**Contents**



## **About the Editor**

## **Nasser A. M. Barakat**

Nasser A. M. Barakat (Professor) obtained his PhD in Chemical Engineering from Hunan University, China in 2004. From 2007 to 2009 he was a postdoctoral Research Fellow at the Bionanosyetm Engineering Department, Jeonbuk National University, Jeonju, South Korea. From 2010 to 2018, he was a faculty member in the Organic Materials and Fiber Engineering Department, Jeonbuk National University, Jeonju, South Korea. Currently, he is working as a professor in the Chemical Engineering Department, Minia University, Egypt. From 2013 to 2018, he was hired a visiting professor in King Saud University, Riyadh, Saudi Arabia. He was selected among the "World Ranking of Top 2% Scientists" in 2021, which was created by experts at Stanford University, USA; he has Rank # 374 (out of 4637) in Energy, and Rank # 683 (out of 6089) in Materials among the top 2% researchers list. According to the AD Scientific Index, in the field of chemical engineering, Prof. Barakat's rank is 1, 1, 2 and 359 in Minia university, Egypt, Africa and the world, respectively.

## **Preface to "Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices"**

Indeed, the precious metals possess fantastic catalytic and electrocatalytic activities; however, the rarity and consequent high cost of these metals forced the applicants to use nonprecious metals as alternatives in the research and industrial fields. Synthesis in nanoscale can distinctly enhance the catalytic activities of the nonprecious metals. The tiny size of the nanostructures makes using them in a free state a difficult task; therefore, the immobilization of the metallic nanostructures on proper supports became an urgen<sup>t</sup> and hot research topic. Advanced energy devices are the most important target to utilize the immobilized nonprecious metals as electrodes. Consequently, writing a book that contains the up-to-date reported strategies in the immobilization of nonprecious metals' nanostructures is highly recommended. Based on the size and morphology of the nanostructures, the immobilization methodology and used support were decided. It was realized that carbonaceous supports, specifically graphene and carbon nanofibers, were widely exploited as supports due to their high adsorption capacity and excellent electric conductivity. Consequently, this book focused on the hot research dealing with these two carbonaceous supports. The editor has carefully selected pioneering researchers in the field of invoking the immobilized nonprecious metals as electrodes in advanced energy devices to contribute to this book. Overall, in this book, the readers will find a valuable collection of fantastic and up-to-date applications of immobilized nonprecious metals on graphene and carbon nanofiber supports as electrocatalysts.

> **Nasser A. M. Barakat** *Editor*

## *Editorial* **Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices**

**Nasser A. M. Barakat**

> Chemical Engineering Department, Minia University, Elminia 61519, Egypt; nasser1995@hotmail.com

The expected near depletion of fossil fuels encourages both the research and industrial communities to focus their efforts to find effective and sustainable alternatives. Electrochemical devices, including fuel cells, batteries, supercapacitors, solar cells, etc., have been found to be the optimal life raft away from this dilemma. Aside from the potential for power generation from untraditional energy sources such as wastewater, electrochemical devices are highly recommended from an environmental point of view. The zero-emission of the exhaust gases greatly helps to solve one of the most dangerous problems currently facing the planet: the increasing climate temperature. Therefore, it would not be an exaggeration to claim that the development of electrochemical devices is considered an existential demand.

In the first era of these promised devices, precious metals such as platinum, palladium, and ruthenium were the main constituents in the manufacture of both cathodes and anodes. However, their high cost constrains the commercial application of these devices [1]. Compared to anodes, precious metal-based compounds as cathode materials were widely exploited. However, the thermodynamic potential of ORR (1.23 V vs. NHE at standard conditions) is so high that the Pt electrode cannot remain pure. Accordingly, the performance decreases due to the formation of PtO [2,3]. Consequently, non-precious metals must be used as electrodes in electrochemical devices not only for cost-decreasing reasons but also for the long-term use of these devices. In this regard, numerous non-precious electrodes have been introduced for different electrochemical devices including fuel cells [4–6], supercapacitors [7], batteries [8], and others [9–12].

Since most of the electrochemical reactions can be considered a combination of adsorption and chemical reaction, carbonaceous materials are widely invoked as supports for different functional materials. Specifically, carbon nanostructures including graphene, carbon nanotubes, and carbon nanofibers show a distinguished enhancement in electrocatalytic activity. Their large surface area and well-known high adsorption capacity improves both mass transfer and reaction(s) kinetics operations. Therefore, different techniques have been proposed for the immobilization of the functional materials on proper supports.

In this regard, this Special Issue entitled "Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices" aims to collect innovative and high-quality research. Along with being a highly informative review article in the field of green hydrogen production, this issue contains nine articles introducing different functional non-precious materials immobilized on various supports. Moreover, the gues<sup>t</sup> editor did his best to focus on popularly discussed topics to draw the maximum amount of attention from the researchers working in the advanced energy devices field. Consequently, a variety of interesting topics are covered in this issue including urea electrooxidation, dye sensitized solar cells, oxygen reduction reactions, and methanol & ethanol electrooxidation.

In summary, the current Special Issue covers cutting-edge techniques for addressing open problems about the use of non-precious metals in the most appealing energy devices and the immobilization of these functional materials on appropriate supports. Finally, the gues<sup>t</sup> editor wishes to thank the editorial staff for their professional help as well as all the contributed authors for their outstanding scholarly contributions.

**Citation:** Barakat, N.A.M. Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices. *Catalysts* **2022**, *12*, 607. https://doi.org/10.3390/ catal12060607

Received: 13 May 2022 Accepted: 25 May 2022 Published: 2 June 2022

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**Copyright:** © 2022 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

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**Conflicts of Interest:** The author declares no conflict of interest.
