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Article

Hydrogen Revolution in Europe: Bibliometric Review of Industrial Hydrogen Applications for a Sustainable Future

by
Diego Vergara
1,*,
Pablo Fernández-Arias
1,*,
Georgios Lampropoulos
2,3 and
Álvaro Antón-Sancho
1
1
Technology, Instruction and Design in Engineering and Education Research Group (TiDEE.rg), Catholic University of Ávila, C/Canteros s/n, 05005 Avila, Spain
2
Department of Applied Informatics, University of Macedonia, 54636 Thessaloniki, Greece
3
Department of Education, University of Nicosia, 1700 Nicosia, Cyprus
*
Authors to whom correspondence should be addressed.
Energies 2024, 17(15), 3658; https://doi.org/10.3390/en17153658
Submission received: 29 June 2024 / Revised: 19 July 2024 / Accepted: 22 July 2024 / Published: 25 July 2024
(This article belongs to the Section A5: Hydrogen Energy)
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Abstract

:
Industrial applications of hydrogen are key to the transition towards a sustainable, low-carbon economy. Hydrogen has the potential to decarbonize industrial sectors that currently rely heavily on fossil fuels. Hydrogen, with its unique and versatile properties, has several in-industrial applications that are fundamental for sustainability and energy efficiency, such as the following: (i) chemical industry; (ii) metallurgical sector; (iii) transport; (iv) energy sector; and (v) agrifood sector. The development of a bibliometric analysis of industrial hydrogen applications in Europe is crucial to understand and guide developments in this emerging field. Such an analysis can identify research trends, collaborations between institutions and countries, and the areas of greatest impact and growth. By examining the scientific literature and comparing it with final hydrogen consumption in different regions of Europe, the main actors and technologies that are driving innovation in industrial hydrogen use on the continent can be identified. The results obtained allow for an assessment of the knowledge gaps and technological challenges that need to be addressed to accelerate the uptake of hydrogen in various industrial sectors. This is essential to guide future investments and public policies towards strategic areas that maximize the economic and environmental impact of industrial hydrogen applications in Europe.

1. Introduction

Hydrogen, a chemical element ubiquitous in the universe, is a key element for the transition to a more sustainable and carbon-free economy, due to its properties as a clean and versatile energy carrier [1]. This colorless gas is found in a wide range of chemical compounds, with water (H2O) being its most common form. Hydrogen, which can be produced from a variety of sources, including renewable energies, represents a promising solution for reducing greenhouse gas emissions in multiple industrial sectors [2]. Hydrogen plays a crucial role in achieving Sustainable Development Goal 7 (SDG 7), which calls for ensuring access to affordable, secure, sustainable and modern energy for all [3]. Traditional methods for hydrogen production are steam methane reforming, coal gasification, biomass gasification, and water electrolysis; however, there exist emerging technologies that have shown promise for efficient hydrogen production [4]. Hydrogen’s ability to store and transport energy efficiently positions it as a key component in the world’s energy future [5].
Hydrogen, with its unique and versatile properties, has several industrial applications [6] that are fundamental for sustainability and energy efficiency (Figure 1), including the following: (i) chemical industry; (ii) metallurgical sector; (iii) transportation; (iv) energy sector; and (v) agri-food sector. One of the most important applications of hydrogen is in the chemical industry, particularly in the production of ammonia [7]. The Haber–Bosch process, which converts hydrogen and nitrogen into ammonia, is essential for the manufacture of fertilizers that support modern agriculture [8]. In addition, hydrogen is used in oil refineries to remove impurities such as sulfur from crude oil [9] thus improving the quality of fuels [10].
In the metallurgical sector, hydrogen plays a crucial role in direct reduction of iron (DRI) [11]. This process uses hydrogen instead of coke to re-reduce iron oxides to metallic iron, resulting in steel production with lower carbon dioxide emissions [12]. This application is particularly relevant in the fight against climate change and in the modernization of steel production, making the process more environmentally friendly and sustainable.
Transportation also benefits significantly from hydrogen [13], especially in applications requiring high energy density and fast refueling times. Hydrogen fuel cell vehicles (FCEVs) [14] are gaining popularity in the commercial transportation sector, including buses, trucks, and heavy-duty vehicles [15]. These vehicles offer the advantage of zero exhaust emissions and can be refueled in comparable times to traditional vehicles [16], making them a viable option for reducing the carbon footprint of transportation [17].
Hydrogen power generation is another industrial application with great potential [18]. Hydrogen power plants can use fuel cells to convert hydrogen into electricity efficiently and without polluting emissions [19]. In addition, hydrogen can be used as a large-scale energy storage medium [20], allowing intermittent renewable energy, such as solar and wind, to be stored and used during periods of high energy demand [21,22,23]. The rise in hydrogen as an energy storage has prompted the implementation of hydrogen generation systems based on electrolyzers [24]. The disruptive solution to energy storage is the solid-state hydrogen storage technology [25].
Finally, the food and electronics industries also benefit from the use of hydrogen. In the food industry, it is used in the hydrogenation of oils and fats [26], improving the texture and stability of food products, as well as in waste management [27,28]. In the electronics industry, hydrogen is essential in the manufacture of semiconductors and advanced materials [29], creating clean and reducing atmospheres necessary for the production of high-purity and high-performance electronic components [30]. These diverse industrial applications highlight the versatility of hydrogen and its potential to transform multiple sectors towards more sustainable and efficient practices.
Conducting a bibliometric review on the industrial applications of hydrogen responds to a critical need in the current context of energy transition and environmental concerns [31,32]. Hydrogen has been highlighted as a promising energy vector with the potential to address key challenges such as decarbonization of energy-intensive industrial sectors, electrification of transport, or in view of its numerous industrial applications [31]. However, a complete understanding of its role and applications in industry requires a thorough evaluation of the available scientific and technical literature.
A bibliometric review can provide an overview of the trends, recent advances, emerging research areas, and knowledge gaps [33]. Thus, in the present bibliometric review, only the research results obtained in the different countries of the European continent are taken into account, and the results obtained will be compared with the hydrogen consumption data per end-use obtained in different European regions in the year 2022 [34]. This comparison of the results obtained in the bibliometric review with the hydrogen end-use consumption will provide a valuable roadmap for researchers, companies, and policymakers, facilitating the identification of collaboration opportunities, areas of innovation, and possible areas of investment to further boost the development and implementation of hydrogen-related technologies in the industrial sector in Europe. Finally, this bibliometric review can be considered when analyzing the evolution of the EU hydrogen strategies [35] and its integration into the energy system (COM/2020/299) [36].
To achieve this research objective, this paper has been structured in the following sections: (i) Materials and Methods: describes in detail the procedure carried out to develop the bibliometric review; (ii) Results: presents the research findings, using tables, graphs and figures to illustrate the data collected; (iii) Discussion: interprets these results and compares them with industrial hydrogen consumption in Europe; and (iv) Conclusions: the main findings are summarized and the contributions of the study are highlighted.

2. Materials and Methods

The bibliographic database Scopus was used for the selection of articles with the aim of covering the largest possible number of scientific results. The reason for using Scopus as the reference bibliographic database is its high impact, as well as the large number of scientific results it contains. The selection of articles was carried out in June 2024. In addition, to increase the precision in the selection of the sample size to be analyzed, the PRISMA protocol guidelines were used. The PRISMA protocol is a guideline used to improve the transparency and quality of systematic reviews and meta-analysis reports. This protocol is structured in several phases as follows [37,38]: (i) Identification, where an exhaustive search of relevant studies is performed in bibliographic databases; (ii) Selection, where the studies found are filtered, eliminating duplicates and assessing the relevance of each one based on the inclusion and exclusion criteria; (iii) Eligibility, where the full texts of the selected studies are reviewed to confirm their adequacy to the pre-established criteria; and (iv) Inclusion, where the finally chosen studies are integrated into the review and analyzed to extract data and synthesize results.
These phases of the PRISMA protocol ensure a rigorous and structured approach, increasing the reproducibility and reliability of systematic reviews [39,40]. Finally, as far as the search string is concerned, several keywords were incorporated together with a combination of Boolean operators ((“Hydrogen” OR “H2”) AND (“industrial applications” OR “industrial use” OR “industrial sector”)).
As shown in Figure 2 below, in the Identification phase, a total of 7274 potentially relevant results were obtained. This large initial dataset underlined the need to have different inclusion and exclusion criteria in the subsequent Screening phase, as well as the need to filter out duplicate studies and those that did not meet the pre-established requirements. The inclusion criterion used was country, including only countries of affiliation, grouped into the following: (i) European Union: Austria, Belgium, Bulgaria, Croatia, Republic of Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain and Sweden; (ii) United Kingdom; and (iii) countries included in the European Free Trade Association (EFTA): Denmark, Switzerland, Iceland and Liechtenstein.
This process reduced the number of studies to 1854 results, which represents a significant elimination of irrelevant results for the present investigation. The elimination of results other than scientific articles reduced the results to 1497. Of these results, only those written in English, 1472, were considered. After review of duplicate results, the population remained at 1471. The more thorough review of titles and abstracts in this phase allowed for a more accurate assessment of the relevance of each study, with 33 being eliminated as irrelevant to the present study. Finally, in the Eligibility phase, a detailed review of the texts of the remaining studies was performed, resulting in the inclusion of 675 studies in the final bibliometric review.
In order to carry out the subsequent bibliometric analysis, the following different software were used: (i) the software environment for statistical computing and graphics R 4.3.3 and the package biblimoetrix; (ii) and VOSviewer 1.6.16, software tool for constructing and visualizing bibliometric networks.

3. Results

First, the most relevant results obtained in this research are shown below. Table 1 contains the main information from the bibliometric analysis performed with Bibliometrix, providing a comprehensive and detailed view of the key results obtained. This table serves as an essential tool to understand the overall research landscape and to identify patterns and trends in scientific production. First, the table shows the total number of papers analyzed (675), which provides an indication of the magnitude of the study. In addition, it includes data on the time period covered by the research (1951–2023), which allows us to contextualize trends and changes over time. Other crucial information includes the annual growth rate (3.63%) and the average citations per doc (89.85). It also identifies the number of results written by a single author (22) and the number of co-authors per doc (5.14).
Figure 3 shows the time trend of research on industrial hydrogen applications in the period 1980–2023. If the complete timespan (1951–2023) is analyzed, it is possible to observe how the interest and scientific activity in Europe has changed over time. In the time period 1951–1988 (Stage I), the interest of the European scientific community in industrial hydrogen applications was practically nonexistent. On the other hand, from 1988 to 2002 (Stage II), it is possible to observe a significant growth of publications, with about 10 articles per year. From 2002 to the present (Stage III), it is possible to observe a stage of rapid growth, with more than 1 article per month (more than 12 articles per year). It is necessary to take into account that as far as research results are concerned, the year 2022 is not yet a consolidated year, for this reason it is not possible to draw conclusions until then.
Table 2 provides a detailed overview of the most influential journals and publications in the field of study that were analyzed (i.e., the top sources). By highlighting the main sources, the table also helps researchers to select suitable journals for the publication of their own work, based on the impact and visibility they offer. The top sources for research on industrial hydrogen applications (Table 2) are “International Journal of Hydrogen Energy” (7.2 impact factor), “Surface and Coatings Technology” (5.4 impact factor), and “Appplied Microbiology and Biotechnology” (5.0 impact factor).
Analysis of the most relevant articles provided an exhaustive analysis of the most influential papers in the field of study, highlighting those that have had the greatest impact on the scientific community. Table 3 includes detailed information on the most relevant articles in the field, including indicators such as “Total Citations”, “Total Citations per Year” (TC per year), and “Normalized Total Citations” (normalized TC). The combination of these indicators provides a more complete and nuanced view of the articles that have contributed significantly to the development of the field of study, identifying both pioneering works and those that continue to influence current research.
Looking at total citations, five of these most cited papers are above 1000: Trovarelli (1996) [41], Mueller (2006) [42], Popov (2004) [43], Kondratenko (2013) [44] and Erdemir (2006) [45]. The TC (total citations) per year indicator allows to evaluate the annual influence of an article, showing how many times it has been cited each year since its publication. This indicator is crucial for understanding the relevance and persistence of an article’s impact over time. Only Trovarelli (1996) [41], Mueller (2006) [42], and Kondratenko (2013) [44] obtained a score higher than 100 on this indicator. On the other hand, normalized CT adjusts total citations according to the year of publication, offering a more equitable comparative perspective between articles published in different years. This indicator is especially useful for assessing the true influence of a paper, eliminating temporal biases and allowing for fairer comparisons between recent and older studies. In this case, the most influential article and not the most cited, being also the most recent, is Kondratenko [44] (2013), which obtained in this indicator a value of 14.82.
The distribution of authors’ publications provides a detailed analysis of the contribution of researchers to the field of study, focusing on the number of articles published and the percentage of professors among the authors. This analysis identifies trends and evaluates the concentration of scientific production. These data suggest a strong influence of the industrial applications of hydrogen in the scientific community, but also the lack of reference researchers in the field (Table 4). This statement is confirmed when analyzing that only 228 authors (7.1% of the total) have written between two and five papers, while only 5 authors (0.16% of the total) have contributed more than five papers on the subject.
On the other hand, Table 5 highlights the institutions with the highest number of publications, providing a measure of leadership and research capacity in the specific area. This not only identifies the main players in research, but also allows an assessment of the geographical distribution of scientific activity. It is possible to identify a strong concentration of researchers in the field in Denmark, with the predominant position of Technical University of Denmark (49 articles) and Aarhus University (22 articles). In second place are central European institutions such as Delft university of Technology (The Netherlands) (18 articles), University of Twente (The Netherlands) (17 articles) and Rwth Aachen University (Germany) (18 articles). Finally, contributions from Southern European countries include the University of Porto (Portugal) (25 articles) and Politecnico di Milano (Italy) (22 articles). It should be noted that there are no relevant institutions in the field in Eastern European countries or in the United Kingdom.
The analysis of the most cited countries in this bibliometric study provides valuable insight into the global influence and impact of research on industrial hydrogen applications in Europe. First, the number of single-country articles (SCP) and the number of multi-collaborative articles (MCP) provide insight into the dynamics of collaboration within and outside the country. A high number of articles reflects a high scientific output (Figure 4). A high SCP indicates a strong independent research output within the country, while a high number of MCP signals a trend towards international collaboration.
The frequency of publication and the MCP ratio provide additional information on the temporal distribution of research and the proportion of multi-collaborative research, which may indicate a more collaborative and global research strategy. In view of the results obtained, Germany and Italy are the countries with the highest scores on these indicators. Spain, France, and United Kingdom are in second place as reference countries in terms of influence and global impact of research on industrial hydrogen applications.
Figure 5 of the most cited countries shows not only the total number of citations (TC) that each country has received, but also the average number of citations per article, which gives a more accurate picture of the impact of the research produced in those countries. The total number of citations (TC) reflects the relevance and visibility of a country’s research in the global scientific community. Italy, Germany, France, United Kingdom, and Belgium are the countries with the highest TC and therefore the countries whose research has been widely recognized and referenced by other researchers, indicating a high quality and relevance of their scientific production. The average number of citations per article, on the other hand, provides a measure of the efficiency and average impact of the articles produced in each country. A high average number of citations per article suggests that, on average, each publication from that country has a significant impact, which may be indicative of a high quality of research and an ability to address relevant issues effectively. As far as research on industrial applications of hydrogen is concerned (Figure 5), the countries with the highest average number of citations per article are Belgium, Greece, Italy, Switzerland, and Germany. It is worth noting the special situation of Greece, which, despite not being one of the countries with the highest TC, obtained the highest number of citations per publication.
Finally, if the keywords are analyzed, firstly, by developing the network of influence between them, in the Figure 6 it is possible to observe the existence of three predominant clusters, namely Cluster I (348 items); Cluter II (151 items); and Cluster III (100 items). The short distance between the keywords indicates a stronger or more frequent association between them in the articles reviewed. This may mean that these terms often appear together in the scientific literature, indicating a close conceptual or thematic link. The size of the circles in a keyword network represents the frequency with which each keyword appears in the corpus of the literature analyzed. In terms of the size of the circles, a larger circle indicates that the corresponding keyword is mentioned more frequently in the articles reviewed, suggesting that it is a central concept or of high relevance in the field of study. For example, the terms “hydrogen” or “industrial applications” are highly recurrent themes in this area of research.
Secondly, to deepen the analysis of the most relevant topics in hydrogen industrial applications research, it is possible to identify the central themes by quantitatively analyzing the most relevant keywords in this field. The occurrences indicator shows the total number of occasions in which the keyword appears, while the total link strength is a crucial metric to quantify and visualize the strength of connections in a network, allowing researchers to identify the most central and influential elements in a field of study.
In the Top 10 most relevant keywords in the field (Table 6), topics such as “hydrogen-ion concentration”, “nonhuman”, “pH”, “chemistry” and “metabolism” stand out. The first three keywords exceed 100 occurrences and have a link strength of more than 3000. The interrelationship between hydrogen ion concentration, pH, chemistry and metabolism in non-human organisms is key to advancing efficient and sustainable industrial applications. The concentration of hydrogen ions is critical as it determines the pH of solutions, significantly affecting the chemistry of industrial processes.
Accurate pH control is vital for optimizing chemical reactions, ensuring efficiency and safety in sectors such as food, drug, and chemical manufacturing. In addition, the study of metabolism in non-human organisms, such as bacteria and fungi, is crucial for industrial biotechnology. These microorganisms are used in the production of biofuels, enzymes, and other compounds of commercial interest [51], where pH adjustment is essential to maximize metabolic activity and production yields.

4. Discussion

First of all, the distribution of topics identified in the bibliometric review previously developed is shown below. It should be borne in mind that a result may be included in different themes. As can be seen in Figure 7, the most relevant topics are those related to chemical applications, with Chemistry and Chemical Engineering accounting for more than 60% of the results. The results related to Materials Science also stand out, mainly due to the importance of hydrogen-assisted embrittlement in materials [52] and Energy and Engineering, with each area having a specific weight of more than 20%. In similar weights are Biochemistry, Genetics and Molecular Biology, Physics and Astronomy, and Environmental Science. The rest of the topics have a minimum specific weight compared to the previous ones.
In the following section, the bibliometric review is further developed, and the scientific results found for the different industrial applications of hydrogen are explored. To achieve this objective, along with the search string initially used: ((“Hydrogen” OR “H2”) AND (“industrial applications” OR “industrial use” OR “industrial sector”)), new additional search criteria related to the different industrial applications of hydrogen are added (Table 7). In view of the results obtained, it is possible to confirm the statement made above about the predominant position of chemical engineering research within the industrial applications of hydrogen.
Germany, United Kingdom, Spain, France, and Italy are the countries with the greatest interest in the different research areas analyzed. Netherlands, appears as one of the countries with greater interest in hydrogen applications for transport and energy, while Poland has a high interest in metallurgical, agricultural, and electronic applications. Finally, Portugal is positioned as a European reference in research on hydrogen applications in the agricultural sector. These results reflect a particular scenario in which Denmark has the most relevant institutions in Europe in terms of research on the industrial applications of hydrogen (Table 5), yet it is not among the most relevant in Europe in terms of research on industrial applications considered in this research.
By comparing these findings with the results obtained in the present bibliometric review with hydrogen consumption data in different European countries [30], a deeper analysis of the situation of industrial hydrogen applications at the European level can be developed. This scenario reflects different hydrogen consumption patterns, depending on their needs and industrial as well as energy policies. Some countries are mainly producers, while others are net consumers. In order to carry out this comparison, it has been necessary to establish a criterion based on the comparison of research results in industrial hydrogen applications and hydrogen consumption in the different applications. This criterion has made it possible to establish different geographical areas (GA) as follows: (i) GA-I: high scientific productivity (more than 100 results) and high hydrogen consumption (more than 550 ky/year); (ii) GA-II: high scientific productivity (more than 100 results) and low hydrogen consumption (less than 100 kt/year); (iii) GA-III: low scientific productivity (less than 100 results) and high hydrogen consumption (greater than 550 ky/year); (iv) GA-IV: low scientific productivity (less than 100 results) and low energy consumption (less than 100 kt/year); and (v) GA-V: low scientific productivity and intermediate energy consumption (less than 550 kt/year and greater than 100 kt/year).
As can be seen in Figure 8, Germany, France, Spain, Italy, Netherlands, and the United Kingdom lead in both scientific production and hydrogen consumption (GA-I), thanks to their ambitious renewable energy projects and systems, and their advanced research. Other countries such as Greece, Portugal, Sweden, and Norway also show notable industrial consumption of hydrogen, supported by national policies that encourage research and development of hydrogen technologies. These countries have been deploying hydrogen in applications such as steel production, refineries and the chemical sector, where green and blue hydrogen are gradually replacing fossil fuels. It is worth noting that there are no countries in GA-II, with high scientific productivity and low hydrogen consumption.
On the other hand, there are no countries with extensive research in the matter that nevertheless consume little hydrogen. Taking into account consumption expectations [30], the existence of a country in these conditions is very complicated and finally, there are countries with still low consumption of hydrogen and little scientific research in this regard, among which are Iceland, Denmark, Croatia, Ireland, Slovenia, etc.
Germany is the major hydrogen consumer, driven by its large industrial base and aggressive decarbonization targets [53]. Meanwhile, Spain is becoming a major producer of green hydrogen, taking advantage of its abundant renewable energy resources [54]. Overall, although Europe has a mix of hydrogen producers and consumers [18], cross-border trade remains essential to meet regional demand and optimize the use of renewable resources [55].
If the six countries located in the GA-I (Germany, France, Spain, Italy, Netherlands, and the United Kingdom) had their hydrogen consumption analyzed according to its different industrial applications (Figure 9), it would be possible to observe that refining is the industrial application with the highest hydrogen consumption in Europe. It is interesting to note that in countries such as Spain, refining, together with ammonia, is the main industrial application of hydrogen, but refining remains the most important. In Italy, hydrogen is used in refineries and the chemical industry, and there are plans to expand its use in transport and power generation [54].
In the other countries, like France and the United Kingdom, in addition to refining and ammonia, other chemical uses have important specific weights in terms of consumption. Finally, Germany and the Netherlands are positioned as the European countries with the most diversified industrial consumption of hydrogen [56], where, in addition to the aforementioned applications, the industrial heat and methanol represent a relevant consumption of hydrogen.

5. Conclusions

Research on the industrial applications of hydrogen has grown and garnered diversified interest in recent years, especially within the European Union. Bibliometric studies reveal a significant increase in the scientific publications related to hydrogen, reflecting the strategic importance that European countries attach to this technology as a sustainable solution for industrial decarbonization. This boom in research aligns with the EU’s goals of reducing carbon emissions and improving energy efficiency in various industrial sectors. The bibliometric analysis highlights interdisciplinary and transnational collaboration, which is crucial to meeting the technical and economic challenges presented by large-scale hydrogen deployment.
The great European power in terms of scientific production and consumption of hydrogen for different industrial applications is Germany. On the other hand, countries such as France, Spain, and Italy, although their production of scientific publications on hydrogen has increased, are still in the initial stages of large-scale industrial adoption. However, these countries are making significant progress in developing pilot projects and building green hydrogen plants, suggesting potential growth in the near future. European policies and investments in infrastructure will be decisive in accelerating this process and achieving the climate objectives established by the European Union.
The need for all European countries to increase their scientific production on the industrial applications of hydrogen is vital so that the continent can position itself as a world power in this emerging field. The transition towards cleaner and more sustainable energies is a global priority, and hydrogen is presented as a key element in this process. Increasing research and development around the industrial applications of hydrogen will allow Europe to not only reduce its dependence on fossil fuels, but also lead technological innovations that could revolutionize various industrial sectors, from manufacturing to agriculture and transport. By encouraging greater collaboration and scientific production, European countries will be able to share knowledge, optimize resources, and accelerate the development of advanced hydrogen technologies, thus strengthening their competitiveness on the global stage and contributing significantly to the fight against climate change.

Author Contributions

Conceptualization and methodology, D.V. and P.F.-A.; validation, D.V., P.F.-A. and Á.A.-S.; formal analysis, P.F.-A.; investigation D.V., P.F.-A. and Á.A.-S.; writing—original draft preparation, D.V., P.F.-A., G.L. and Á.A.-S.; writing—review and editing, D.V. and P.F.-A.; supervision, G.L. and Á.A.-S.; project administration, D.V. and P.F.-A. All authors have read and agreed to the published version of the manuscript.

Funding

Diputación de Ávila (Spain) for the project 2020–2024 PT 2022_002, in the framework of CTC, Innovation and Entrepreneurship of the Territorial Development Programme of Ávila and its Surroundings.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding authors.

Acknowledgments

The authors wish to acknowledge the financial support provided by the following Spanish Institutions: Diputación de Ávila (Spain), in the framework of CTC, Innovation and Entrepreneurship of the Territorial Development Programme of Ávila and its Surroundings.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Industrial applications of hydrogen.
Figure 1. Industrial applications of hydrogen.
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Figure 2. Outline of the PRISMA Protocol.
Figure 2. Outline of the PRISMA Protocol.
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Figure 3. Scientific production evolution of industrial applications of hydrogen in Europe.
Figure 3. Scientific production evolution of industrial applications of hydrogen in Europe.
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Figure 4. Top 10 most relevant European countries by corresponding author.
Figure 4. Top 10 most relevant European countries by corresponding author.
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Figure 5. Top 10 most cited European countries.
Figure 5. Top 10 most cited European countries.
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Figure 6. Net of the most relevant keywords.
Figure 6. Net of the most relevant keywords.
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Figure 7. Status of research on industrial hydrogen applications in different European countries throughout the 21st Century.
Figure 7. Status of research on industrial hydrogen applications in different European countries throughout the 21st Century.
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Figure 8. European status of research on industrial applications and hydrogen consumption.
Figure 8. European status of research on industrial applications and hydrogen consumption.
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Figure 9. European hydrogen consumption by end-use in industrial applications.
Figure 9. European hydrogen consumption by end-use in industrial applications.
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Table 1. Main information about the bibliometric review.
Table 1. Main information about the bibliometric review.
DescriptionResults
Main information about data
Timespan1951–2023
Sources (Journals, Books, etc.)329
Documents675
Annual Growth Rate %3.63
Document Average Age11.9
Average citations per doc89.85
References0
Document contents
Keywords Plus (ID)7782
Author’s Keywords (DE)2118
Authors
Authors3169
Authors of single-authored docs22
Authors collaboration
Single-authored docs22
Co-Authors per Doc5.14
International co-authorships %44.44
Document types
article553
conference paper12
letter1
review108
short survey1
Table 2. Principal scientific sources on this topic.
Table 2. Principal scientific sources on this topic.
SourcesResults
International Journal of Hydrogen Energy32
Surface and Coatings Technology18
Applied Microbiology and Biotechnology13
Industrial and Engineering Chemistry Research13
Chemical Engineering Journal11
Chemsuschem9
Journal of Biotechnology9
Acs Applied Materials and Interfaces8
chemical engineering science8
renewable and sustainable energy reviews8
Table 3. Most global cited papers about industrial applications of hydrogen.
Table 3. Most global cited papers about industrial applications of hydrogen.
PaperReferenceTotal
Citations		TC
per Year		Normalized TC
Trovarelli, A. (1996)[41]3326114.695.50
Mueller, U. (2006)[42]2046107.689.14
Popov, V.N. (2004)[43]173582.628.16
Kondratenko, E.V. (2013)[44]1491124.2514.82
Erdemir, A. (2006)[45]105455.474.71
Welton, T. (2018)[46]66494.868.28
Cametti, M. (2009)[47]62839.256.21
Chavali, M.S. (2019)[48]57595.8310.51
de Vos, R.M. (1998)[49]55520.562.62
Bewilogua, K. (2014)[50]46242.005.35
Table 4. Most global cited papers about industrial applications of Hydrogen.
Table 4. Most global cited papers about industrial applications of Hydrogen.
Documents WrittenNo. of AuthorsProportion of Authors
1293892.71%
21885.93%
3290.92%
490.28%
520.06%
610.03%
710.03%
810.03%
Table 5. Most relevant affiliations about industrial applications of hydrogen in Europe.
Table 5. Most relevant affiliations about industrial applications of hydrogen in Europe.
PositionAffiliationCountryArticles
1Technical University of Denmark Denmark49
3University of PortoPortugal25
4Aarhus universityDenmark22
5Politecnico di MilanoItaly22
6Abo Akademi universityFinland22
7Delft university of technologyThe Netherlands18
8Rwth Aachen UniversityGermany18
9University of TwenteNetherlands17
Table 6. Most relevant keywords about industrial applications of hydrogen.
Table 6. Most relevant keywords about industrial applications of hydrogen.
PositionKeywordOccurrencesTotal Link Strength
1hydrogen-ion concentration1173271
2Nonhuman1053145
3pH1093116
4Chemistry962497
5Metabolism802263
6industrial applications1402190
7Temperature822066
8priority journal842003
9enzyme activity551928
10unclassified drug601778
Table 7. Additional search string and results (data collected from Scopus database in June 2023).
Table 7. Additional search string and results (data collected from Scopus database in June 2023).
Industrial ApplicationAdditional Search StringResultsCountries
ChemicalAND (“Ammonia” OR “Methanol” OR “refining” OR “blending” OR “Chemi *”)770Germany, United Kingdom, Spain, France, Italy
Metallurgical AND (“Steel” OR “iron”)154Germany, United Kingdom, Spain, France, Italy, Poland
TransportAND (“movility” OR “transport” OR “cell”)324Germany, United Kingdom, Spain, France, Italy and Netherlands
EnergyAND (“energy” OR “generation” OR “electricity”)533Germany, United Kingdom, Spain, France, Italy and Netherlands
AgrifoodAND (“fertilizers” OR “agro *” OR “agricu *”)50Germany, United Kingdom, Poland, Italy, Portugal and Greece
ElectronicalAND (“electronical” OR “electro *”)452Germany, United Kingdom, Spain, France, Italy, Poland
* represents 0 or more characters.
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Vergara, D.; Fernández-Arias, P.; Lampropoulos, G.; Antón-Sancho, Á. Hydrogen Revolution in Europe: Bibliometric Review of Industrial Hydrogen Applications for a Sustainable Future. Energies 2024, 17, 3658. https://doi.org/10.3390/en17153658

AMA Style

Vergara D, Fernández-Arias P, Lampropoulos G, Antón-Sancho Á. Hydrogen Revolution in Europe: Bibliometric Review of Industrial Hydrogen Applications for a Sustainable Future. Energies. 2024; 17(15):3658. https://doi.org/10.3390/en17153658

Chicago/Turabian Style

Vergara, Diego, Pablo Fernández-Arias, Georgios Lampropoulos, and Álvaro Antón-Sancho. 2024. "Hydrogen Revolution in Europe: Bibliometric Review of Industrial Hydrogen Applications for a Sustainable Future" Energies 17, no. 15: 3658. https://doi.org/10.3390/en17153658

APA Style

Vergara, D., Fernández-Arias, P., Lampropoulos, G., & Antón-Sancho, Á. (2024). Hydrogen Revolution in Europe: Bibliometric Review of Industrial Hydrogen Applications for a Sustainable Future. Energies, 17(15), 3658. https://doi.org/10.3390/en17153658

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