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Article

Exsolved Nanoparticles Decorated Double Perovskites as High-Performance Anodes for Direct-Ammonia Solid Oxide Fuel Cells

by
Yongning Yi
1,†,
Jiaming Chen
1,†,
Meigui Xu
1,
Guangming Yang
1,
Ran Ran
1,
Wei Zhou
1,
Wei Wang
1,* and
Zongping Shao
1,2,*
1
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 210009, China
2
WA School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, Perth, WA 6845, Australia
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Catalysts 2023, 13(6), 996; https://doi.org/10.3390/catal13060996
Submission received: 8 May 2023 / Revised: 1 June 2023 / Accepted: 9 June 2023 / Published: 12 June 2023
(This article belongs to the Special Issue Research Advances in Electrocatalysts for Fuel Cells)
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Abstract

:
Due to the high energy density, mature production technology, ease of storage and transportation, and the no carbon/sulfur nature of ammonia fuel, direct-ammonia solid oxide fuel cells (DA-SOFCs) have received rapidly increasing attention, showing distinct advantages over H2-fueled SOFCs and low-temperature fuel cells. However, DA-SOFCs with conventional Ni-based cermet anodes still suffer from several drawbacks, including serious sintering and inferior activity for ammonia decomposition, strongly limiting the large-scale applications. To tackle the above-mentioned issues, exsolved NiCo nanoparticles decorated double perovskite oxides are fabricated and employed as high-performance anodes for DA-SOFCs in this work. By optimizing the Ni doping amount in Sr2CoMo1−xNixO6−δ (x = 0.1, 0.2 and 0.3), the reduced Sr2CoMo0.8Ni0.2O6−δ (r-SCMN2) anode exhibits superb catalytic activity for ammonia cracking reaction and high anti-sintering capability. More specifically, the electrolyte-supported single cell with r-SCMN2 nanocomposite anode delivers superior power outputs and operational durability in ammonia fuel as compared with other r-SCMN anodes owing to the significantly promoted nanoparticle exsolution and stronger interaction between alloy nanoparticles and the support. In summary, this study presents an effective strategy for the design of efficient and stable nanocomposite anodes for DA-SOFCs.

Graphical Abstract

1. Introduction

In recent years, due to ever-increasing environmental pollution and energy crisis caused by the excessive utilization of fossil fuels such as global warming and climate change, the development of advanced technologies for the utilization of alternative clean and sustainable energies has attracted increasing attention [1,2,3,4,5,6,7]. Fuel cells are considered as highly promising energy conversion devices due to low emissions and high efficiencies [8,9,10,11,12,13,14]. Particularly, solid oxide fuel cells (SOFCs) exhibit distinct merits over other fuel cells, such as all-solid structure and fuel flexibility [15,16,17,18,19]. In theory, all the combustible fuels can be used for SOFCs, such as hydrogen (H2), ammonia (NH3), and hydrocarbons [20,21,22,23,24]. However, the H2 fuel for SOFCs suffers from several drawbacks, such as no natural sources and limited infrastructures for the transport and storage [25,26,27,28]. Compared to H2, hydrocarbons, including methane and natural gas, are more promising as fuels for SOFCs owing to the ease in transportation and abundant resources. However, the conventional nickel (Ni)-based anodes in SOFCs suffer from severe sulfur poisoning and carbon deposition when using hydrocarbon fuels, greatly restricting the long-term stability of SOFCs [29,30,31]. Therefore, the utilization of carbon/sulfur-free fuels is highly crucial for high-performance and durable SOFCs. Ammonia (NH3) is a carbon/sulfur-free fuel with the advantages of high volumetric energy density, ease in transportation/storage, and matured synthesis technology. It has attracted particular interests as a promising fuel for SOFCs recently [32,33,34,35].
Based on the potential reactions in the anode chamber of direct-ammonia (DA)-SOFCs [36], the ideal anodes should show high (electro)catalytic activity for NH3 decomposition reactions (NDR) and H2 oxidation reactions (HOR). Although the conventional Ni-based anodes exhibited superior HOR activity, they still suffered from serious particle agglomeration and low NDR activity at lower temperatures, leading to inferior power outputs and operational durability of DA-SOFCs [37]. Therefore, the design and development of alternative anodes to replace Ni-based cermets are highly crucial to achieve highly efficient and durable DA-SOFCs. Perovskite oxides have been regarded as promising anodes for DA-SOFCs due to their excellent structural and compositional flexibility and high chemical and thermal stability [38,39,40,41,42]. However, pure perovskite-based anodes suffer from low catalytic activity for NDR and HOR [43,44]. Thus, perovskite oxides have been employed as promising substrates to support in situ exsolved metal nanoparticles (NPs), exhibiting superior (electro)catalytic activity/stability for both NDR and HOR by stabilizing the surface NPs [36,45,46,47]. For instance, we have fabricated La0.55Sr0.30TiO3−δ-based anode with exsolved NiCo alloy NPs for DA-SOFCs, showing considerable (electro)catalytic activity and stability owing to the strong interaction between the exsolved NPs and substrate, outstanding anti-sintering capability, and the balance of NH3 adsorption and N2 desorption processes. The single cell with exsolved NPs composite anode exhibited a high PPD of 361 mW cm−2 at 800 °C and favorable operational stability of 120 h at 700 °C operated on NH3 fuel [45]. Nevertheless, such nanocomposite suffered from limited NDR catalytic activity, which was attributed to the inferior catalytic activity of La0.55Sr0.30TiO3−δ substrate for NDR, restricting the further enhancement in the performance of DA-SOFCs. Therefore, it is important to design efficient perovskite oxide-based support with the exsolved NPs to realize highly efficient and durable DA-SOFCs. Very recently, we have reported a slightly Ru substitution strategy to facilitate the exsolution of alloy NPs in active Pr0.6Sr0.4Co0.2Fe0.8O3−δ (PSCF)-based matrix. The slightly Ru doping effectively increased the amount of exsolved NPs with remarkably reduced particle sizes, and enhanced the nanoparticle/substrate interaction as compared with the Ru-free counterpart, remarkably boosting the (electro)catalytic performance of the anode for NDR and HOR [46]. DA-SOFCs with the Ru-doped anode exhibited much higher PPDs than DA-SOFCs, with PSCF anode at 800 °C and better operational durability.
Double perovskite oxides (A′A″B′B″O6−δ), as an important class of perovskite oxides, have also been reported as efficient anodes for SOFCs due to the higher electrical conductivity and better chemical/thermal stability than those of single perovskites (ABO3) [48,49,50,51,52,53]. However, there are few investigations of double perovskite oxides as anodes for DA-SOFCs due to the inferior NDR catalytic activity of pure-phase double perovskites. Thus, the combination of NPs exsolution and double perovskite-based substrates may be a potential and useful strategy to enhance the performance of perovskite-based anodes for DA-SOFCs. Herein, Sr2CoMo1−xNixO6−δ (SCMN, x = 0.1, 0.2, and 0.3; denoted as SCMN1, SCMN2, and SCMN3, respectively) double perovskites are employed as efficient substrates to anchor alloy NPs through exsolution for the application as anodes for DA-SOFCs. Upon optimizing the Ni doping amount in SCMN, SCMN2 nanocomposite anode exhibited the highest (electro)chemical activity for NDR and HOR due to the promoted NPs exsolution in terms of smaller particle size and higher amounts of exsolved NiCo alloy NPs, much improved anti-sintering capability, and enhanced interaction between NPs and double perovskite matrix. Consequently, SCMN2-based DA-SOFCs delivered higher power outputs and better durability than those with SCMN1, SCMN3, and conventional Ni-based cermet anodes. This work provides an effective and simple strategy for designing highly anti-sintering, active, and stable nanocomposite anodes for DA-SOFCs, promoting the practical applications of this technology.

2. Results and Discussion

The crystal structural information of various SCMNs and reduced Sr2CoMo1−xNixO6−δ (r-SCMN, x = 0.1, 0.2, and 0.3; denoted as r-SCMN1, r-SCMN2, and r-SCMN3, respectively) perovskite oxides were analyzed by X-ray diffraction (XRD), with results displayed in Figure 1a,b and Figure S1. Similar to Sr2CoMoO6−δ (SCM), the as-synthesized SCMN samples exhibited a tetragonal structure and no NiO phases were detected [54], demonstrating the successful doping of Ni into the SCMN perovskite lattice (Figure 1a). As depicted in Figure 1b and Figure S1, after the treatment at 800 °C in pure H2 for 1 h, three SCMN samples with different Ni doping contents exhibited phase transitions accompanied by the exsolution of NiCo NPs and/or the impurity phases [45]. It should be noted that excessive exsolution of B-site cations in SCMN with higher Ni doping concentration may lead to the destruction of the perovskite structure [55]. The main phase of SCMN1 and SCMN2 was changed from Sr2CoMoO6−δ to Sr3MoO6 (JCPDS No.00-027-1441) [56] while the main phases of SCMN3 were Sr3Mo2O7 (JCPDS No.00-052-1252) [57] and SrMoO4 (JCPDS No.01-085-0809) [58] after the reduction. H2 temperature-programmed reduction (H2-TPR) was used to investigate the reducibility and NPs/substrate interaction in various SCMN samples as depicted in Figure 1c. As can be seen, the SCMN samples with larger Ni doping amounts exhibited much higher NPs/substrate interaction as evidenced by the higher temperatures on H2 consumption peaks. SEM was employed to obtain the morphological information of various SCMN perovskites before and after the reduction treatment as depicted in Figure S2 and Figure 1d–f. The as-prepared SCMN samples showed smooth surface and micron-sized particles (Figure S1). After reduction, numerous NPs were exsolved from the double perovskite lattice, which were uniformly distributed on the surface of SCMN substrate. Furthermore, r-SCMN2 displayed a much larger amount of exsolved NiCo NPs with remarkably reduced particle sizes as compared with the r-SCMN1 and r-SCMN3 (Figure 1d–f), leading to the increased Brunauer–Emmett–Teller (BET) specific surface area of r-SCMN2, as depicted in Figure S3.
To further investigate the exsolution behavior of alloy NPs in r-SCMN1, r-SCMN2, and r-SCMN3 samples, scanning transmission electron microscope (STEM)-energy-dispersive X-ray (EDX) and high-resolution (HR)-transmission electron microscopy (TEM) were employed as displayed in Figure 2, Figures S5 and S6. Numerous NPs with an average particle size of ∼20 nm were observed in r-SCMN2 anode, which were well distributed and partially anchored on the substrate surface, indicating a strong interaction between the NPs and the substrate (Figure 2a) [59]. Based on the HR-TEM images in Figure 2b, lattice spacings of around 0.291, 0.197, and 0.205 nm were observed in r-SCMN2 anode, corresponding to the (440), (002), and (111) diffraction planes of Sr3MoO6, Sr2(CoNi)MoO6, and NiCo alloy, respectively. On the contrary, r-SCMN1 and r-SCMN3 samples exhibited a much smaller amount of exsolved NiCo alloy NPs with a much larger average particle size of ~50 nm than those of r-SCMN2 (Figures S4 and S5), demonstrating that the proper Ni doping amount in SCM was beneficial for the exsolution of NiCo alloy NPs. The STEM-EDX results also confirmed the successful exsolution of NiCo alloy NPs in all the three reduced SCMN samples (Figure 2c,d, Figures S4 and S5).
X-ray photoelectron spectroscopy (XPS) technique was used to analyze the oxidation states of various SCMN and r-SCMN anodes, as depicted in Figure 3 and Figure S6. As can be seen, no obvious changes were observed in the Sr 3d spectra of SCMN2 and r-SCMN2 samples (Figure 3b), while the Mo5+/Mo6+ ratio of SCMN2 sample was slightly increased after reduction as depicted in Figure 3c. In addition, the Co 2p spectra of unreduced SCMN samples showed two broad peaks (Figure 3d), which were fitted to two subpeaks of Co3+ (796.9 and 780.0 eV) and Co2+ (795.1 and 781.7 eV), respectively. After reduction, XPS spectra for Co cations of r-SCMN2 were fitted into three subpeaks of Co3+ (795.5 and 780.0 eV), Co2+ (797.2 and 781.5 eV), and Co0 (794.4 and 779.2 eV), indicating the successful Co cation exsolution from the perovskite lattice [55,60]. Similar to Co 2p, the Ni 2p in SCMN2 were mainly expressed as Ni2+ species (855.6 eV), while Ni0 species were observed at 853.8 eV in Ni 2p XPS spectra of r-SCMN2 [47,61]. Furthermore, the amount of Co0 species in r-SCMN2 was much higher than those of r-SCMN1 and r-SCMN3, demonstrating the promoted NiCo alloy NPs exsolution induced by proper Ni doping concentration.
It is well known that ideal anodes for DA-SOFCs should exhibit excellent catalytic activity and durability for NDR. Thus, the catalytic activities of various r-SCMN anodes for NDR were evaluated as displayed in Figure 4a. Three r-SCMN anodes all exhibited high NH3 conversion rates of around 100% at 750–800 °C. In addition, the r-SCMN2 showed higher catalytic activity than those of r-SCMN1 and r-SCMN3 at reduced temperatures due to the higher amount and smaller particle sizes of exsolved NiCo alloy NPs. For instance, the r-SCMN2 anode exhibited a much higher NH3 conversion rate of 89.4% at 650 °C than those of r-SCMN1 (79.3%) and r-SCMN3 (71.6%). As depicted in Figure 4b, the durability of r-SCMN2 sample for NDR at 800 °C was also tested. As can be seen, the r-SCMN2 anode showed a highly durable NH3 conversion rate at around 98% during 242 h for NDR test, highlighting the superior stability of r-SCMN2 anode for DA-SOFCs.
To evaluate the performance of various r-SCMN anodes in practical DA-SOFCs, electrolyte-supported SOFCs with a configuration of r-SCMN anode/Sm0.2Ce0.8O1.9 (SDC) electrolyte/Sm0.5Sr0.5CoO3−δ (SSC) cathode were prepared and tested. The thicknesses of the anode, electrolyte, and cathode were around 15, 350, and 15 µm, respectively (Figure S7). To estimate the potential phase reaction between SDC electrolyte and r-SCMN anodes, SDC and SCMN2 samples were mixed by physical mixing at a weight ratio of 1:1, which was then annealed in air at 1000 °C for 2 h. As displayed in Figure S8, no obvious phase reactions between the SDC electrolyte and r-SCMN2 anode were observed based on the XRD patterns. As depicted in Figure S9a,e, the cell with r-SCMN2 anode delivered high peak power densities (PPDs) of 465, 380, 314, and 239 mW cm−2 at 800, 750, 700, and 650 °C in H2 and 350, 266, 194, 141 mW cm−2 at 800, 750, 700, and 650 °C in NH3. For comparison, the single cell with Ni-SDC anode was also tested in H2 and NH3 fuels. The cells with r-SCMN1, r-SCMN2, r-SCMN3, and Ni-SDC anodes generated PPDs of 437, 465, 409, and 281 mW cm−2 at 800 °C in H2, respectively (Figure 5a). The cells with r-SCMN2 exhibited a high PPD of 437 mW cm−2 at 800 °C in H2, which was 1.06, 1.13, and 1.65 times more than those of the cells with r-SCMN1, r-SCMN3, and Ni-SDC anodes, respectively. After switching from H2 to NH3 fuel, the cells with r-SCMN1, r-SCMN2, r-SCMN3, and Ni-SDC anodes produced PPDs of 327, 350, 296, and 219 mW cm−2 at 800 °C in NH3, respectively (Figure 5b). The r-SCMN2-based cell shows the high PPD of 350 mW cm−2 at 800 °C in NH3, which was 1.07, 1.18, and 1.59 times higher than those of the cells with r-SCMN1, r-SCMN3, and Ni-SDC anodes, respectively. The higher power outputs of r-SCMN2 anode-based single cell in H2 and NH3 fuels were attributed to the higher amount and smaller particle sizes of exsolved NiCo NPs, providing more active centers for NDR and HOR. However, the cells with r-SCMN1, r-SCMN2, r-SCMN3, and Ni-SDC anodes exhibited lower PPDs in NH3 fuel than those of the cells that operated on H2 fuel (Figure S9 and Table S1), which may be assigned to the unreacted NH3 and/or the dilution effect of N2 products.
Based on the electrochemical impedance spectroscopy (EIS) profiles of single cells with various anodes in Figure 5c,d and Table S2, the cell with r-SCMN2 exhibited much lower polarization resistance (Rp) compared to the r-SCMN1, r-SCMN3, and Ni-SDC anodes in both H2 and NH3 fuels, agreeing well with the I-V and I-P results, which was assigned to the higher (electro)catalytic activity for NDR and HOR. The r-SCMN2-based cell exhibited low Rp of 0.027, 0.041, 0.063, and 0.198 Ω cm2 in H2 at 800 to 650 °C and 0.041, 0.054, 0.158, 0.410 Ω cm2 in NH3 at 800 to 650 °C. More specifically, the r-SCMN2-based cell exhibited a much lower Rp of 0.063 Ω cm2 than those of the cells with r-SCMN1 (0.095 Ω cm2), r-SCMN3 (0.203 Ω cm2), and Ni-SDC (0.437 Ω cm2) as anodes in NH3 fuel at 800 °C. It should be noted that both the ohmic resistance (Ro) and Rp values of the cells in NH3 fuel were obviously larger than those of H2-fueled SOFCs with various anodes, as shown in Figure S10, due to the endothermic nature of NDR and the incomplete decomposition of NH3 fuel, leading to decreased real operational temperatures and increased Ro/Rp values. In addition, the power output of DA-SOFCs with r-SCMN2 anode was higher than most of the DA-SOFCs with reported anodes in the literature (Table S3) [31,45,46,62,63,64], further demonstrating the superiority of r-SCMN2 nanocomposite anode for DA-SOFCs.
It has been reported that the conventional Ni-based anodes suffered from severe sintering operated on NH3 fuel at elevated temperatures, strongly restricting the long-term operational durability of DA-SOFCs [65]. Therefore, it is important to evaluate the operational durability of DA-SOFCs with alternative perovskite-based anodes. The stability tests of the cells with various r-SCMN and Ni-SDC anodes were conducted under the conditions of NH3 fuel, 100 mA cm−2, and 800 °C, with the results displayed in Figure S11. The SOFCs with r-SCMN1, r-SCMN2, r-SCMN3, and Ni-SDC anodes exhibited voltage degradation rates of 0.91, 0.74, 0.98, and 14.6 mV h−1, respectively. It is clearly observed that DA-SOFCs with r-SCMN anodes showed superior operational stability to that of the cell with Ni-SDC anode, which was assigned to the better anti-sintering capability of r-SCMN anodes than that of Ni-SDC anode in NH3 fuel (Figure S12). Furthermore, r-SCMN2-based cell displayed better durability for 250 h than those of r-SCMN1 and r-SCMN3-based cells in NH3 fuel, which was attributed to the stronger interaction between the double perovskite substrate and exsolved NPs, which effectively inhibited the NPs aggregation.

3. Materials and Methods

3.1. Synthesis and Fabrication

The powders of SCMN anodes, SSC cathode, and SDC electrolyte were synthesized via a sol–gel route [66,67]. For a typical synthesis, stoichiometric amounts of Sr(NO3)2, Co(NO3)2·6H2O, (NH3)4Mo7O24·6H2O, and Ni(NO3)2·6H2O were heated at 80 °C under stirring. Ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) were added to act as complexing agents at a molar ratio of 1:1:2 for total metal ions, EDTA and CA, in order to mix the metal ions evenly. NH3·H2O was used to adjust the pH value of the aqueous solution to around 7. An atropurpureus gel was obtained after the removal of water in the solution by evaporation, which was pre-decomposed at 200 °C to obtain the precursors. The as-synthesized precursors were then annealed at 1100 °C for 6 h in air to obtain the final products. The SSC cathode and SDC electrolyte were also prepared via the same method, and the samples were annealed at 1000 °C for 5 h and 800 °C for 5 h, respectively. The r-SCMN samples were prepared by treating the SCMN powders in pure H2 atmosphere at 800 °C for 1 h. The SDC pellets were obtained by dry-pressing and were annealed at 1400 °C for 10 h. The anode and cathode slurry were prepared by mixing the powders in isopropanol, glycol and glycerol with a ball milling process (30 min, 400 rpm), spray-painted on the different sides of the electrolyte with an active area of 0.45 cm2, which were annealed at 1000 °C for 2 h in air. Finally, silver pastes and silver wires were used as collector and current lead for single cell, respectively. The operation temperature range of single cell ranged from 650 to 800 °C.

3.2. Characterization

XRD (D8 advance Bruker, Germany) with Cu-Kα radiation was employed to analyze the crystal structures of the samples by using a receiving slit of approximately 0.2–0.4 mm. The data were tested in a step-scan model between 2θ = 10–90° with intervals of 0.02°. TEM (FEI Tecnai G2 F30), STEM, and field emission scanning electron microscopy (FE-SEM, JEOL-S4800) were used to examine the microstructures of the powders and single cells. EDX analyzer (FEI Tecnai G2 F30 STWIN) was employed to obtain EDX mapping images operated at 300 kV. Thermo ESCALAB 250 was used to acquire XPS spectra. BET-specific surface areas of various samples were investigated by obtaining the nitrogen adsorption–desorption isotherms on a Quantachrome AutoSorb-iQ3 instrument at liquid nitrogen temperature. H2-TPR was investigated by the BELCAT-A equipment with a thermal conductivity detector (TCD). The catalytic activities of various samples for NDR were tested in a quartz tube reactor at 500–800 °C [68]. About 0.2 g of anode particles were placed in the reactor. The flow rates of NH3 and Ar (diluting gas) were fixed at 10 and 80 mL min−1 [STP], respectively. A gas chromatograph (GC-9860) with a chromatographic column (PLOT Q) and a TCD was used to analyze the gas compositions after NDR. The Keithley 2420 source meter was used to measure I-V and I-P curves of single cells through the 4-probe mode. The H2 and NH3 fuels were fixed at 80 mL min−1 [STP] at the anode side of the cell, while the cathode side was exposed to the air. EIS profiles of single cells were acquired by a Solartron 1260 frequency response analyzer and Solartron 1287 potentiostat under open circuit voltage conditions, with frequencies ranging from 0.1 to 1 MHz.

4. Conclusions

In this work, SCMN double perovskites were employed as efficient substrates to construct nanocomposite anodes for DA-SOFCs by NPs exsolution strategy. By tailoring the Ni doping concentration in SCMN, the r-SCMN2 nanocomposite exhibited superior (electro)catalytic activity for NDR and HOR, which was attributed to the promoted alloy NPs exsolution and enhanced interaction between substrate and NPs as compared with r-SCMN1 and r-SCMN3 anodes. The single cell with r-SCMN2 anode displayed a high PPD of 350 mW cm−2 and a reasonable operational stability of 250 h with a voltage degradation rate of 0.74 mV h−1 in NH3 fuel at 800 °C, outperforming the cells with the r-SCMN1, r-SCMN3, and Ni-SDC anodes because of the better anti-sintering capability, stronger interfacial interaction, and higher amount of active centers for NDR. This work reports a highly active and durable double perovskite-based nanocomposite anode for DA-SOFCs, accelerating the practical applications of DA-SOFCs.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal13060996/s1, Figure S1: XRD patterns of reduced SCMN and SCM samples; Figure S2: SEM images of (a) SCMN1, (b) SCMN2 and (c) SCMN3 samples; Figure S3: Nitrogen adsorption/desorption isotherms of SCMN1, SCMN2 and SCMN3 samples (a) before and (b) after the reduction; Figure S4: (a) TEM, (b) HR-TEM, (c) STEM and (d) EDX mapping images of r-SCMN1 sample; Figure S5: (a) TEM, (b) HR-TEM, (c) STEM and (d) EDX mapping images of r-SCMN3 sample; Figure S6: XPS spectra of SCMN1 and SCMN3 samples before and after the reduction: (a,d) XPS survey, (b,e) Co 2p and (c,f) Mo 3d; Figure S7: Typical cross-sectional SEM images of a fuel cell with r-SCMN2 anode; Figure S8: XRD patterns of SDC, SCMN2 and SDC+SCMN2 composite (1:1, weight ratio) prepared by physical mixing after a calcination at 1000 °C for 2 h in air; Figure S9: I-V and I-P curves of SOFCs with (a,d) r-SCMN1, (b,e) r-SCMN2 and (c,f) r-SCMN3 anodes operated on H2 (a–c) and NH3 (d–f) fuels at 650–800 °C; Figure S10: EIS spectra of SOFCs with (a,d) r-SCMN1, (b,e) r-SCMN2 and (c,f) r-SCMN3 anodes operated on H2 (a–c) and NH3 (d–f) fuels at 650–800 °C; Figure S11: Operational stability of single cells with r-SCMN1, r-SCMN2, r-SCMN3 and Ni-SDC anodes operated on NH3 fuel under a certain current density of 100 mA cm−2 at 800 °C. Figure S12: SEM images of (a,b) Ni-SDC, (c,d) r-SCMN1, (e,f) r-SCMN2 and (g,h) r-SCMN3 anodes before (a,c,e,g) and after (b,d,f,h) the treatment in NH3 fuel at 800 °C for 30 h; Table S1: PPDs comparison of the single cells with r-SCMN anodes at different temperatures in H2 and NH3 fuels; Table S2. Rp of the single cells with r-SCMN anodes at different temperatures in H2 and NH3 fuels; Table S3: PPDs comparison of DA-SOFCs with r-SCMN1, r-SCMN2 and r-SCMN3 anodes developed in this work and other representative anodes reported in the literature.

Author Contributions

Investigation, formal analysis, visualization, writing—original draft, data curation, validation, Y.Y. and J.C.; writing—review and editing, funding acquisition, M.X.; writing—review and editing, G.Y. and R.R.; project administration, W.Z.; supervision, conceptualization, writing—review and editing, funding acquisition, W.W.; supervision, writing—review and editing, Z.S. All authors have read and agreed to the published version of the manuscript.

Funding

This work is supported by National Natural Science Foundation of China (No. 22279057 and 22108121).

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflict of interest.

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Catalysts 13 00996 g001 550
Figure 1. (a) XRD patterns of various SCMN samples. (b) XRD patterns of SCMN2 and r-SCMN2 samples. (c) H2-TPR profiles of various SCMN samples. SEM images of (d) r-SCMN1, (e) r-SCMN2, and (f) r-SCMN3 samples.
Figure 1. (a) XRD patterns of various SCMN samples. (b) XRD patterns of SCMN2 and r-SCMN2 samples. (c) H2-TPR profiles of various SCMN samples. SEM images of (d) r-SCMN1, (e) r-SCMN2, and (f) r-SCMN3 samples.
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Figure 2. (a) TEM, (b) HR-TEM, (c) STEM, and (d) EDX mapping images of r-SCMN2 sample.
Figure 2. (a) TEM, (b) HR-TEM, (c) STEM, and (d) EDX mapping images of r-SCMN2 sample.
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Figure 3. XPS spectra of SCMN2 and r-SCMN2 samples: (a) XPS survey, (b) Sr 3d, (c) Co 2p, (d) Mo 3d, and (e) Ni 2p. (f) Co 2p spectra of r-SCMN1, r-SCMN2, and r-SCMN3 samples.
Figure 3. XPS spectra of SCMN2 and r-SCMN2 samples: (a) XPS survey, (b) Sr 3d, (c) Co 2p, (d) Mo 3d, and (e) Ni 2p. (f) Co 2p spectra of r-SCMN1, r-SCMN2, and r-SCMN3 samples.
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Figure 4. (a) Catalytic activity of various r-SCMN anodes for NDR at 500–800 °C. (b) Catalytic stability test of the r-SCMN2 anode for NDR at 800 °C.
Figure 4. (a) Catalytic activity of various r-SCMN anodes for NDR at 500–800 °C. (b) Catalytic stability test of the r-SCMN2 anode for NDR at 800 °C.
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Figure 5. I-V and I-P curves of single cell with various r-SCMN and Ni-SDC anodes in (a) H2 and (b) NH3 fuels at 800 °C with corresponding EIS spectra in (c) H2 and (d) NH3 fuel.
Figure 5. I-V and I-P curves of single cell with various r-SCMN and Ni-SDC anodes in (a) H2 and (b) NH3 fuels at 800 °C with corresponding EIS spectra in (c) H2 and (d) NH3 fuel.
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Yi, Y.; Chen, J.; Xu, M.; Yang, G.; Ran, R.; Zhou, W.; Wang, W.; Shao, Z. Exsolved Nanoparticles Decorated Double Perovskites as High-Performance Anodes for Direct-Ammonia Solid Oxide Fuel Cells. Catalysts 2023, 13, 996. https://doi.org/10.3390/catal13060996

AMA Style

Yi Y, Chen J, Xu M, Yang G, Ran R, Zhou W, Wang W, Shao Z. Exsolved Nanoparticles Decorated Double Perovskites as High-Performance Anodes for Direct-Ammonia Solid Oxide Fuel Cells. Catalysts. 2023; 13(6):996. https://doi.org/10.3390/catal13060996

Chicago/Turabian Style

Yi, Yongning, Jiaming Chen, Meigui Xu, Guangming Yang, Ran Ran, Wei Zhou, Wei Wang, and Zongping Shao. 2023. "Exsolved Nanoparticles Decorated Double Perovskites as High-Performance Anodes for Direct-Ammonia Solid Oxide Fuel Cells" Catalysts 13, no. 6: 996. https://doi.org/10.3390/catal13060996

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