This review summarizes the recent research progress made in nanostructured metal nitrides for electrochemical and photo(electro)chemical water splitting.

In the last decade, perovskite solar cells (PSCs) have undergone unprecedented rapid development and become a promising candidate for a new‐generation solar cell. Among various PSCs, typical 3D halide perovskite‐based PSCs deliver the highest efficiency but they suffer from severe instability, which restricts their practical applications. By contrast, the low‐dimensional Ruddlesden–Popper (RP) perovskite‐based PSCs have recently raised increasing attention due to their superior stability. Yet, the efficiency of RP perovskite‐based PSCs is still far from that of the 3D counterparts owing to the difficulty in fabricating high‐quality RP perovskite films. In pursuit of high‐efficiency RP perovskite‐based PSCs, it is critical to manipulate the film formation process to prepare high‐quality RP perovskite films. This review aims to provide comprehensive understanding of the high‐quality RP‐type perovskite film formation by investigating the influential factors. On this basis, several strategies to improve the RP perovskite film quality are proposed via summarizing the recent progress and efforts on the preparation of high‐quality RP perovskite film. This review will provide useful guidelines for a better understanding of the crystallization and phase kinetics during RP perovskite film formation process and the design and development of high‐performance RP perovskite‐based PSCs, promoting the commercialization of PSC technology.

The fabrication art of the membrane electrode assembly (MEA) in a proton-exchange membrane (PEM) fuel cell strongly correlates to the cell performance. It has been recognized that defects, for example, high interfacial resistance between the catalyst layers (CLs) and the membrane or cracks in the CLs, may occur during the MEA manufacturing process. These defects could greatly influence the electrochemical performance of the fuel cell. To eliminate those defects and improve the cell performance, in this study, a novel fabrication approach of the MEA for PEM fuel cells is developed. With this method, the Nafion ionomer, employed as a PEM, is directly coated onto both the cathode and anode CLs. As a result, not only an excellent interfacial connection between the PEM and CLs is achieved with a low interfacial resistance, but also cracks are eliminated due to Nafion ionomer penetration into the cracks, forming hydrophilic channels with ionic conduction. Those ionic conduction channels improve the water management, lower the mass transport loss, and facilitate the proton transfer, thus maximizing the three-phase boundary and enhancing the utilization of Pt/C catalysts. By adding an expanded polytetrafluoroethylene film, a favorable mechanical property of the MEA is also achieved. This novel MEA exhibits excellent cell performance under low humidity conditions. Under the H 2 /air operation, the cell performance reaches a high maximum power density of 1.35 W cm −2 .

The present work investigates the application of a Nafion separator in aqueous zinc ion batteries.

Cobalt phosphides electrocatalysts have great potential for water splitting, but the unclear active sides hinder the further development of cobalt phosphides. Wherein, three different cobalt phosphides with the same hollow structure morphology (CoP‐HS, CoP2‐HS, CoP3‐HS) based on the same sacrificial template of ZIF‐67 are prepared. Surprisingly, these cobalt phosphides exhibit similar OER performances but quite different HER performances. The identical OER performance of these CoPx‐HS in alkaline solution is attributed to the similar surface reconstruction to CoOOH. CoP‐HS exhibits the best catalytic activity for HER among these CoPx‐HS in both acidic and alkaline media, originating from the adjusted electronic density of phosphorus to affect absorption–desorption process on H. Moreover, the calculated ΔGH* based on P‐sites of CoP‐HS follows a quite similar trend with the normalized overpotential and Tafel slope, indicating the important role of P‐sites for the HER process. Moreover, CoP‐HS displays good performance (cell voltage of 1.67 V at a current density of 50 mA cm−2) and high stability in 1 M KOH. For the first time, this work detailly presents the critical role of phosphorus in cobalt‐based phosphides for water splitting, which provides the guidance for future investigations on transition metal phosphides from material design to mechanism understanding.

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