Developing robust and highly active bifunctional electrocatalysts for overall water splitting is critical for efficient sustainable energy conversion. Herein, heteroatom-doped amorphous/crystalline ruthenium oxide-based hollow nanocages (M-ZnRuOx (MCo, Ni, Fe)) through delicate control of composition and structure is reported. Among as-synthesized M-ZnRuOx nanocages, Co-ZnRuOx nanocages deliver an ultralow overpotential of 17 mV at 10 mA cm-2 and a small Tafel slope of 21.61 mV dec-1 for hydrogen evolution reaction (HER), surpassing the commercial Pt/C catalyst, which benefits from the synergistic coupling effect between electron regulation induced by Co doping and amorphous/crystalline heterophase structure. Moreover, the incorporation of Co prevents Ru from over-oxidation under oxygen evolution reaction (OER) operation, realizing the leap from a monofunctional to multifunctional electrocatalyst and then Co-ZnRuOx nanocages exhibit remarkable OER catalytic activity as well as overall water splitting performance. Combining theory calculations with spectroscopy analysis reveal that Co is not only the optimal active site, increasing the number of exposed active sites while also boosting the long-term durability of catalyst by modulating the electronic structure of Ru atoms. This work opens a considerable avenue to design highly active and durable Ru-based electrocatalysts.

Heteroatom Doped Amorphous/Crystalline Ruthenium Oxide Nanocages as a Remarkable Bifunctional Electrocatalyst for Overall Water Splitting.

Hydrogen energy is regarded as the ultimate energy source for future human society, and the preparation of hydrogen from water electrolysis is recognized as the most ideal way. One of the key factors to achieve large-scale hydrogen production by water splitting is the availability of highly active and stable electrocatalysts. Although non-precious metal electrocatalysts have made great strides in recent years, the best hydrogen evolution reaction (HER) electrocatalysts are still based on noble metals. Therefore, it is particularly important to improve the overall activity of the electrocatalysts while reducing the noble metals load. Alloying strategies can shoulder the burden of optimizing electrocatalysts cost and improving electrocatalysts performance. With this in mind, recent work on the application of noble metal-based alloy electrocatalysts in the field of hydrogen production from water electrolysis is summarized. In this review, first, the mechanism of HER is described; then, the current development of synthesis methods for alloy electrocatalysts is presented; finally, an example analysis of practical application studies on alloy electrocatalysts in hydrogen production is presented. In addition, at the end of this review, the prospects, opportunities, and challenges facing noble metal-based alloy electrocatalysts are tried to discuss.

Design and Synthesis of Noble Metal-Based Alloy Electrocatalysts and Their Application in Hydrogen Evolution Reaction.

Pt loading-dependent transport kinetics and effectiveness of Pt in proton exchange membrane fuel cells

Proton exchange membrane fuel cell (PEMFC) is one of the most promising energy conversion devices with high efficiency and zero emission. However, oxygen reduction reaction (ORR) at the cathode is still the dominant limiting factor for the practical development of PEMFC due to its sluggish kinetics and the vulnerability of ORR catalysts under harsh operating conditions. Thus, the development of high‐performance ORR catalysts is essential and requires a better understanding of the underlying ORR mechanism and the failure mechanisms of ORR catalysts with in situ characterization techniques. This review starts with the introduction of in situ techniques that have been used in the research of the ORR processes, including the principle of the techniques, the design of the in situ cells, and the application of the techniques. Then the in situ studies of the ORR mechanism as well as the failure mechanisms of ORR catalysts in terms of Pt nanoparticle degradation, Pt oxidation, and poisoning by air contaminants are elaborated. Furthermore, the development of high‐performance ORR catalysts with high activity, anti‐oxidation ability, and toxic‐resistance guided by the aforementioned mechanisms and other in situ studies are outlined. Finally, the prospects and challenges for in situ studies of ORR in the future are proposed.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/advs.202300550

Progress and Perspective for In Situ Studies of Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

https://doi.org/10.1016/j.isci.2023.106730

Engineering carbon semi-tubes supported platinum catalyst for efficient oxygen reduction electrocatalysis

It remains a challenge for platinum-based oxygen reduction reaction catalysts to simultaneously possess high mass activity and high durability in proton-exchange-membrane fuel cells. Herein, we report ultrathin holey nanotube (UHT)-structured Pt-M (M = Ni, Co) alloy catalysts that achieve unprecedented comprehensive performance. The nanotubes have ultrathin walls of 2-3 nm and construct self-supporting network-like catalyst layers with thicknesses of less than 1 μm, which have efficient mass transfer and 100% surface exposure, thus enabling high utilization of Pt atoms. Combined with the high intrinsic activity produced by the alloying effect, the catalysts achieve high mass activity. Moreover, the nanotube structure not only avoids the agglomeration problem of nanoparticles, but the low curvature of the tube wall also gives UHT a low surface energy (less than 1/3 of that of the same size nanoparticle), so UHT is more resistant to the Ostwald ripening and is stable. For the first time, the U.S. DOE mass activity target and dual durability targets for load and start-stop cycles are achieved on one catalyst. This study provides an effective structural strategy for the preparation of electrocatalysts with high atomic efficiency and excellent durability.

Ultrathin Nanotube Structure for Mass-Efficient and Durable Oxygen Reduction Reaction Catalysts in PEM Fuel Cells.

Formamidinium lead bromide (FAPbBr3) nanocrystals (NCs) have been demonstrated to exhibit ideal ultrapure green luminescence at 530 nm and to hold great potential in light-emitting diodes, by potentially overcoming the difficulties facing cesium lead bromide (CsPbBr3) NCs. However, compared to all-inorganic lead halide perovskite NCs, organic–inorganic hybrid FAPbBr3 NCs are sensitive to moisture, oxygen, and heat due to their intrinsic instability caused by the organic cations (FA+). Herein, we present an epitaxial growth method for the overgrowth of a large-band-gap cesium lead halide (Cs4PbBr6) shell on the surface of FAPbBr3 NCs. The resulting core/shell NCs show a near-unity photoluminescence quantum yield (PLQY) of 97.1%, the emission with full width at half-maxima of 88 meV, and long-term environmental stability. The introduction of Cs+ into FAPbBr3 NCs can inhibit the migration of FA+ and suppress the phase transformation from cubic phase to tetragonal phase at 60 °C. Furthermore, the existence of shell can provide stronger exciton confinement and improve the thermal stability of FAPbBr3 NCs. The core/shell perovskite NCs developed in this study have the advantages of high PLQY and good stability and may contribute to the field of light-emitting diodes (LEDs). 

Weiwei Chen

Papers

Ultrathin Nanotube Structure for Mass-Efficient and Durable Oxygen Reduction Reaction Catalysts in PEM Fuel Cells.

FAPbBr3/Cs4PbBr6 Core/Shell Perovskite Nanocrystals with Enhanced Stability and Emission: Implications for LEDs

A sodium-ion-conducted asymmetric electrolyzer to lower the operation voltage for direct seawater electrolysis