Electrochemical water splitting plays a critical role in high purity hydrogen production. To lower capital cost and energy consumption, efficient catalysts are required to boost the hydrogen evolution reaction (HER), especially in alkaline media. Although PtRu alloy materials are still considered the state-of-the-art catalyst for the HER under alkaline media, large-scale application is hindered by its scarcity and high cost. NiMo alloy catalysts can be potential Pt-free alternatives to drive the sluggish kinetics of the HER under alkaline media, but their HER activity is still not ideal due to the limitation of Volmer step. Herein, we investigated the impact of trace levels of PtRu catalysts on NiMo electrodes towards the HER by incorporating advantages of both PtRu and NiMo catalysts to minimize cost and maintain a promising HER activity. Trace levels of PtRu catalysts from 0.0173 to 0.2648 mg cm(-2) were loaded on commercial NiMo foam electrodes by a facile electrodeposition technique utilizing ppm concentration levels of PtRu in electrolyte. The results show that 0.0173 mg cm(-2) PtRu loading on NiMo electrode can significantly enhance HER activity compared to the pristine NiMo foam electrode (Tafel slopes drop from similar to 170 to similar to 60 mV dec(-1)) due to the remarkable decline of energy barriers towards water dissociation and hydrogen adsorption. Meanwhile, the rate determining step (RDS) switches from the Volmer step to the Heyrovsky step when the PtRu loading increases to 0.0675 mg cm(-2). Promising catalytic stability is observed at 100 mA cm(-2) over the course of 50 h with a PtRu loading of 0.1198 mg cm(-2). This work demonstrates a potential strategy to decrease the cost and simultaneously maintain superior HER performance by integrating trace levels of PtRu catalyst with NiMo foam electrodes.

Metallic interconnects in direct methanol solid oxide fuel cells (SOFCs) are prone to being oxidized during operation, leading to electrical degradation and compromising the overall performance of the stack. The oxidation behavior of SUS441 stainless steel and the protective effect of a La0.2Sr0.8TiO3-s (LST) coating were investigated under a methanol-steam atmosphere at 750 degrees C, relevant to anode atmosphere. LST coatings, synthesized via solid-state reaction and was applied by screen printing. After 1000 h oxidation, coated SUS441 formed only a approximate to 4.8 mu m thick oxide scale, compared to approximate to 11.6 mu m on uncoated steel. The area-specific resistance increased moderately (9.67-16.36 mS2 center dot cm2), significantly lower than uncoated samples (216.46 mS2 center dot cm2). The oxidation rate constant decreased by an order of magnitude. These results highlight the efficiency of LST coating in enhancing oxidation resistance and electrical stability. Furthermore, the details about protective mechanisms of LST coating are illustrated.

A series of commercial Oxygen Evolution Reaction (OER) IrO2-based materials doped with acid-stable titanium and niobium species were comprehensively characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS), and X-ray Scattering. Electrocatalysts were integrated into Membrane Electrode Assembly (MEA) using a fabrication method developed under the US DOE H2NEW consortium. An electrolysis performance in a commercial setup as well as a laboratory screening system was performed at conditions relevant to industrial application. According to the comprehensive characterizations, the studied materials are closer to doped iridium oxides rather than core-shell structures. In an electrolysis cell, the IrO2/TiOx catalyst slightly outperforms the IrO2/NbOx based on the activity. It was demonstrated that the operation of electrolysis cells at elevated temperatures and the implementation of thinner Nafion-type membranes allows for substantially increased performance, which is consistent with the literature report. This work provides valuable baselines including characterization and performance for guiding future research in this direction.

In the past few decades, tremendous attention has been devoted to enhancing the activity of oxygen evolution reaction (OER) catalysts for hydrogen production, while the cost and long-term stability of catalysts, which can play an even more important role in industrialization, have been much less emphasized. Herein, we engineered an OER electrode from abundant stainless steel (SS) via facile approaches, and the obtained electrode consists of a Ni-rich oxide surface layer with a Fe-rich metal substrate. An outstanding activity was observed with an overpotential of 316 mV at 100 mA cm-2 in 1 M KOH electrolyte. Additionally, an electrode self-replenishing concept is proposed in which a Ni-rich catalyst layer can be regenerated from a metallic substrate due to the difference in diffusion and dissolution rates of metal oxides/hydroxides, and this regeneration is validated by various characterizations. A recorded degradation rate of 0.012 was observed at 1000 mA cm-2 for 1000 h. The facile engineering of OER electrodes from SS combined with the self-replenishing catalyst can potentially address the cost, activity, and long-term stability barriers.

In the past few decades, tremendous attention has been devoted to enhancing the activity of oxygen evolution reaction (OER) catalysts for hydrogen generation, while the cost and long-term stability of OER catalysts, which can play an even more important role in large-scale electrolysis industrialization, have been much less emphasized. Herein, we engineered an OER electrode from cheap and abundant stainless steel (SS) via facile approaches. An outstanding activity is observed with a low overpotential at 10 mA cm-2 and a small Tafel slope, which is among the best performances in the published literature. Additionally, a self-repairing catalyst concept on the electrode is proposed in which the Ni-rich catalyst layer can regenerate from the metallic substrate under the OER induction due to the different diffusion and dissolution rates of metal oxides/hydroxides. The facile engineering of OER electrodes from SS combined with the self-repairing catalyst can potentially address the cost and long-term stability barriers for OER catalysts in alkaline electrolysis.

High-performance catalysts are extremely required for controlling NH3 emission via selective catalytic oxidation (SCO), and the anchoring structural feature of active sites is a key prerequisite for developing them. This study confirms the importance of hydroxyl groups on vacancy-deficient reducible oxides as active groups. On the one hand, spontaneous atomic dispersion of active metal Ir is promoted by the abundant terminal hydroxyl groups. On the other hand, Ir cations anchor on the TiO2 surface through exchange with H+ in Ti-OH groups, and thus occupy the Bronsted acid sites. The adsorption strength of NH3 is another key factor affecting the reaction rate-determining step, namely NH3 dehydrogenation, which occurs at a faster rate in the coordinated L-NH3 rather than the ionic B-NH4+. Meanwhile, the coordinated L-NH3 significantly avoids the competitive adsorption of water vapor in the NH3-SCO reaction by reducing the number of hydrogen bonding. The TOF of preferred 0.8Ir/TiO2 sample is significantly higher than 0.2Ir/TiO2 sample, although Ir is almost always atomic dispersed. Finally, NH3 conversion is 85% in a wet circumstance (5% H2O) at 240(degrees)C (GHSV = 85 000 h(-1)), with a N-2 selectivity of up to 65% on 0.8Ir/TiO2 sample.

Low ionic conductivity and unsatisfactory mechanical properties of the solid polymer electrolytes hinder their applications of in solid-state lithium metal batteries. Herein, we design a polymer-in-salt solid electrolyte (PISSE) with multiple Li+ transport paths and crosslinked polymer chain networks, endowing the PISSE with both high mechanical strength and high ionic conductivity. The optimized PISSE can therefore reach ionic conductivity of 3.03x10-4 S cm-1 (25 degrees C) and the mechanical strength of 0.811MPa. The percolation model explains that the salt-rich clusters account for the extra fast ion transfer paths; whereas, the crosslinking structure compensates the loss of mechanical strength at high salt concentration. Finally, the in situ polymerization of PISSE promotes the electrode-electrolyte interface compatibility, resulting in the Li//PISSE60%@LiFePO4 cells with 71% (initial capacity: 111.8 mAh g- 1) of capacity retention after 800 cycles at 0.5 C. Moreover, the PISSE also exhibits compatibility with high voltage cathode LiFe0.2Mn0.8PO4 cells up to 4.3V. Therefore, this work provides a practical strategy to fabricate stable solid electrolytes for next-generation lithium metal batteries.

Lithium-sulfur batteries (LSBs) with high energy density are promising for energy storage. However, conventional polypropylene-based separator cannot avoid polysulfides shuttling which impedes the practical application of LSBs. Herein, an in-situ ionothermal synthesis strategy that concurrently applies ionic liquid as the solvent, template and high-yield carbon source is proposed for the facile preparation of nanoporous carbon/oxide composite separator modifiers. The composites exhibit features of high polarity, self doping, oxygen vacancy, heteroatom doping, abundant defects and high electronic conductivity. Theoretical and experimental studies suggest that the composites can efficiently trap and convert polysulfides for high-performance LSBs. Indeed, in the composite-modified LSBs with next-generation roll-to-roll dry-processed high-loading sulfur cathodes, enhanced performance is achieved, revealing the effectiveness of the composites as functional materials towards separator modification. Therefore, the proposed strategy and its delivered nanoporous composites exhibit excellent versatility and practicality for high-performance LSBs.

Metal-supported solid oxide fuel cells (MS-SOFCs) have attracted increasing attention due to their superior mechanical strength, relatively low material cost, and capability of fast thermal cycling, as compared to the conventional all-ceramic solid oxide fuel cell. However, fabrication of MS-SOFCs still remains challenging. This study reports a cost-effective powder metallurgical manufacturing route for producing MS-SOFCs. Stainless steel 430L (SS430L) powder is selected for producing the metal support due to its relatively low cost and good thermal expansion compatibility. MS-SOFC button cells with the SS430L/YSZ|Ni/YSZ|YSZ|LSCF structure were successfully prepared by co-sintering and ultrasonic pyrolytic spraying. We found that the trace oxygen level in the dilute H 2 /Ar gas mixture could play a drastic role in laboratory sintering of the SS430L support; local oxygen control is essential, particularly to avoid Cr oxidation. The addition of no more than 10% YSZ as a second phase to SS430L substantially minimized over-sintering of the SS430L support, leading to a more porous metallic-type substrate, while the electrical conductivity and thermal expansion were not much affected. The fabricated MS-SOFC button cells with the SS430L/YSZ|Ni/YSZ|YSZ|LSCF structure delivered a maximum power density of 180 mW cm -2 at 800°C with an open-circuit voltage of 1.13 V, using dry hydrogen as the fuel and ambient air as an oxidant. A cell tested at 750°C showed relatively good stability for a period of 140 h. While the performance still needs further optimization, the high OCV and good stability indicated that the reported powder metallurgy route is a promising method, and the relevant experimental details, particularly on producing metallic and oxidation-free porous supports, are critical for the preparation of MS-SOFCs.

A novel acetic-acrylic (AA) approach was developed to obtain La0.6Sr0.4CoO3−δ (LSC) using lanthanum oxide, acetate, and acrylic acid as the starting materials. We synthesized several LSC products with varying acrylic acid (L) and metal salt (M) molar ratios (L/M). The precursors and the final products were thoroughly characterized. When the L/M molar ratio is 0.9, the high-purity nano LSC powders were obtained by heating at 900 °C. The conductivity of LSC bulk sample was equal to 2534 and 2430 S cm−1 at 650 and 700 °C, respectively. This sintered LSC was used in a cathode with polarisation resistances (Rp) of 0.190 and 0.084 Ω·cm2 at 650 and 700 °C, respectively. It was observed that at 700 and 650 °C, the power density of an anode with a structure that might be defined as Ni-3YSZ/8YSZ/GDC/LSC-0.9 was 947 and 585 mW cm−2, respectively. Our results revealed that the high-performance LSC powders could be synthesized by the acetic-acrylic synthesis method, applicable to a large scale.

Hundreds of oxygen evolution reaction (OER) electrocatalysts have been developed over the past few decades, and their performances are evaluated and compared at ambient temperature. However, the effect of ambient temperature variation on OER electrocatalyst performance has received less attention, which may play a remarkable role in the electrocatalytic activity. In this work, we systematically investigated the influence of ambient temperature variation on electrocatalyst performance toward OER. The results show that the slight ambient temperature variation has a significant effect on OER catalyst performance based on the changes of overpotential (10 mA cm-2) and Tafel slope. Both remarkable chances are observed on transition metal (Ni) and noble metal (IrO2) electrocatalysts, and the overpotentials decrease around 81 mV with a temperature increase by 20 degrees C (from 10 degrees to 30 degrees C) for both Ni and IrO2 electrocatalysts with the Tafel slope drops of 36.9 and 29.5 mV dec-1, respectively. A similar trend is also found in the electrochemically active surface (ECSA) normalized performance and the charge transfer resistance. This study demonstrates that reporting the actual operating temperature for OER is not only recommended but also necessary to evaluate and compare electrocatalyst activities from different materials systems properly, and neglecting the ambient temperature variation effect can highly mislead conclusions.

Two commercially available stainless steel mesh substrates (316 SS and 304 SS) were evaluated as electrodes for oxygen evolution reaction (OER) in natural seawater electrolysis. The results show the 304 SS is less stable against corrosion under neutral (pH of 8.5) and low alkaline (0.1 M NaOH, pH of 12.8) seawater electrolytes because of the direct metal dissolution and chlorine evolution reaction (CER), and the 316 SS is superior to 304 SS in terms of electrocatalytic activity and resistance to corrosion under the same media. The performance of 304 SS is comparable to 316 SS under the high alkaline (1 M NaOH, pH of 13.7) seawater electrolyte, where the CER and metal dissolution are suppressed by OER. The overpotential for 304 and 316 SS is around 430 mV at 10 mA cm-2, and the Tafel slopes are below 50 mV dec-1 under the high alkaline (1 M NaOH) seawater electrolyte, showing promising performance. The poor resistance to corrosion of 304 SS is attributed to the low Mo content, and it is supposed that the stability of both 304 and 316 SS can be improved further with the addition of Mo content. This work expands on promising substrates for natural seawater electrolysis, with cost and performance advantages.

Solid oxide fuel cell (SOFC) is an electrochemical device for power generation with high efficiency and low emission. Ammonia is a low-cost and carbon-free hydrogen carrier that can be directly used as a fuel for SOFC. To further improve the performance and stability of SOFC fueled by ammonia (NH3–SOFC), the design of NH3–SOFC anode for efficient and stable utilization of NH3 is critical. In this paper, the decomposition rates of NH3 over four kinds of cheap metal catalysts (nickel, iron, copper and 304 stainless steel) were tested based on metal flakes with known fixed dimensions, and the empirical correlations of the decomposition rate over different catalysts were derived. These correlations are independent of catalyst structure parameters and only related to the catalyst material and the decomposition temperature, which are important basis for realizing the oriented design of NH3–SOFC anode.

Methane is regarded as one of the ideal fuels for solid oxide fuel cell (SOFC) due to its huge reserves and transportation properties. In this study, a 3D numerical model coupling with chemical reaction, electrochemical reaction, mass transfer, charge transfer, and heat transfer is developed to understand the heat and mass transfer processes of methane steam direct internal reforming based on double-sided cathodes (DSC) SOFC. After the model verification, the parametric simulations are performed to study the effects of operating voltage, inlet temperature, and steam to carbon (S/C) ratio on the performance of a DSC. It is found that the non-uniform distribution of flow rate among channels results in non-uniform distribution of each physical field. Increasing the inlet temperature significantly enhances the performance of DSC, however, when the temperature is above 1073 K, the concentration loss and the temperature gradient of DSC increase, which is not conducive to the long-term operation of the DSC. In addition, we revealed the effect of the S/C ratios on the heat and mass transfer process. This study provides an insight into the heat and mass transfer process of SOFC with a mixture of steam and methane and operating conditions for enhancing the performance.

One of the key challenges for ammonia-fed anion exchange membrane fuel cells is to the ammonia electro-oxidation reaction (AEOR) at anode, which has sluggish kinetics and generates atomic nitrogen (N-ads) poisoning the Pt catalyst. In this study, a comparative study on Pt/Ta3N5, Pt/Ta2O5, Pt/carbon black, and Pt plate are conducted in order to clarify the promoting effect of the support materials for Pt catalysts. X-ray photoelectron spectroscopy analysis and density functional theory calculations reveal that the support materials significantly affect the electron condition of the Pt, resulting in the tuned adsorption energy of N-ads on Pt surface. The electrochemical analysis demonstrates that the weakened adsorption of N-ads lowers the coverage of N-ads on Pt surface, resulting in the enhanced performance and stability of Pt catalysts for AEOR. In particular, Pt/Ta3N5 catalyst exhibits a current density of 5.92 mA cm(-2) of AEOR at -0.34 V vs. SCE, which is higher than that of Pt/Ta2O5 (2.56 mA cm(-2), -0.35 V vs. SCE) and Pt/C (4.45 mA cm(-2), -0.26 V vs. SCE). The achievements in this study demonstrate the importance of controlling the type of supports for the development of an active electrocatalyst for continuous AEOR. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Ammonia is regarded as a promising alternative fuel for solid oxide fuel cells (SOFCs) compared with hydrogen due to its low cost and ease for transportation and storage. The conventional anode Ni/yttria-stabilized zirconia (Ni/YSZ) of SOFCs can serve as an efficient catalyst for ammonia decomposition at high temperatures above 700 degrees C but its catalytic activity decreases rapidly at lower temperatures, leading to an undesirable degradation of cell performance. Here we report a low-temperature ammonia decomposition catalyst Ba-modified Ni/yttria-stabilized zirconia (Ba-Ni/YSZ) prepared by a one-pot solid-liquid (SL) method. Enhanced performance can be obtained for Ba-Ni/YSZ compared with that of Ni/YSZ catalysts, indicating that the addition of Ba promotes the catalytic activity. X-ray photoelectron spectroscopy (XPS) and Temperature-programmed reduction with H-2 (H-2-TPR) characterizations of Ba-Ni/YSZ catalysts indicate that Ba changes the electronic structure of Ni and facilitates the interaction between Ni and support. The kinetics analysis demonstrates that the modification by a small amount of Ba species alleviated the negative effect of the hydrogen poisoning on the active sites of Ni/YSZ catalysts. Besides, the Ba-Ni/YSZ catalyst is introduced into the flat-tube SOFC with symmetric double-sided cathodes (DSC), and significantly improves the electrochemical performance of directly ammonia-fed DSC cells at low temperatures. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

Reversible solid oxide cells have received increasing attention due to high efficiency. Cobalt-free perovskite electrode has compatible thermal expansion coefficient matching with the electrolyte and the reversible operation to inhibit the segregation of Sr. Herein a novel cobalt-free La0.6Sr0.4Fe0.8Ni0.2O3-delta perovskite is developed and investigated as oxygen electrode for reversible solid oxide cells. The electrochemical performance of La0.6Sr0.4Fe0.8Ni0.2O3-delta oxygen electrode in fuel cell mode and electrolysis mode is investigated in detail. The maximum power density of 961 mW cm(-2) and polarization resistance of 0.142 52 cm(2) at 800 degrees C can be achieved in fuel cell mode. While the cell is operated in electrolysis mode, the current density ranges from 0.53 A cm(-2) at 750 degrees C to 1.09 A cm(-2) at 850 degrees C with 50 vol % absolute humidity at 1.3 V, and the hydrogen generation rate can reach up to 1348.5 mL (cm(2) h)(-1) with 90 vol % absolute humidity at 800 degrees C. The reversible solid oxide cells show excellent reversibility and stability during 144 h medium-term reversible operation. The results indicate that La0.6Sr0.4Fe0.8Ni0.2O3-delta has a bright prospect as the oxygen electrode material for reversible solid oxide cells.

Solid oxide fuel cells (SOFCs) possess excellent fuel flexibility, which enlarges the field of application of SOFCs. Herein, we report flat-tube SOFCs with double-sided cathodes (DSC). Such structure has inner channels across the anode support of the cell, and thus provide a chamber for the internal reforming of the fuels. Moreover, the symmetric structure and thick anode support of the DSC cells significantly enhances the structural strength of the cell. In this study, hydrogen, ammonia, and humidified hydrocarbons including methane, coke oven gas, and ethanol were supplied to the anode of the flat-tube SOFCs. The cell performance and long-term stability against the kinds of main fuels, the content of water, the temperatures, and the current density were investigated in details. In addition, the catalytic processes of these fuels within the anode were estimated by analyzing the exhaust gases.

Fe3C (cementite) is a widely used material with excellent mechanical and magnetic properties; therefore the preparation method of Fe3C has been widely concerned. In this paper, dense and high-purity bulk Fe3C samples were prepared based on the solid-phase reaction of iron and carbon under high temperature and high pressure, and the influence of raw material type, particle size, sintering temperature, pressure, and holding time are investigated for the sintered samples. It shows that the densest samples were produced under the sintering pressure and temperature of 4 GPa and 1000 ̊C when the Fe and graphite particles were 9 \begin{document}$ {\text{μ}}{\rm{m}}$\end{document} and 1.3 \begin{document}$ {\text{μ}}{\rm{m}}$\end{document} respectively.

采用固液复合法合成了钐钕共掺杂的氧化铈(Sm0.075Nd0.075Ce0.85O2-δ:SNDC).研究了球磨罐、球磨珠材质和球磨转速对粉体物相、成分、形貌及烧结行为的影响.结果表明:制备的SNDC物相纯净,为近似球型的纳米粉体.采用聚四氟乙烯罐和氧化锆球磨珠所制粉体纯度高.采用氧化铝球磨罐或球磨珠会引入杂质Al、Si和Ca.采用氧化铝罐和氧化锆球磨珠会额外引入Zr和Y,且球磨转速400 r/min杂质引入量高于300 r/min的.掺杂YSZ明显抑制了SNDC烧结,Al2O3可促进SNDC烧结,降低烧结致密温度约200℃.