Photocatalysis is a promising and convenient strategy to convert solar energy into chemical energy for various fields. However, photocatalysis still suffers from low solar energy conversion efficiency. Developing state of the art photocatalysts with high efficiency and low cost is a huge challenge. Transition metal nitrides (TMNs) as a class of metallic interstitial compounds have attracted significant attention in photocatalytic applications. In fact, TMNs exhibit multifunctional properties in various photocatalytic systems. This review is the first attempt that summarizes recent research on TMNs‐based materials in various photocatalytic applications. Different roles of TMNs materials in photocatalytic systems including semiconductor active components, co‐catalysts, inter‐band excitation, and surface plasmon resonance components are systematically discussed and summarized. The fundamentals, latest progress, and emerging opportunities for further improving the performances of TMNs‐based materials for photocatalysis are also discussed. Finally, some challenges facing TMNs, and perspectives on their future that are relevant for furthering research in the area of photocatalysis are also proposed.

Transition metal nitrides are of considerable interest for energy conversion and storage applications. Given this, synthesis of nanostructured 3D transition metal nitrides is of contemporary interest. Here, a hard templating simple and efficient pathway to synthesize 3D ordered‐mesoporous ternary nitrides NiCo2N is reported using the mesoporous silica KIT‐6 hard template. Benefitting from its large surface area and accessible pores, uniform shape, and enhanced infiltration capacity for electrolyte, mesoporous NiCo2N demonstrates superior electrode performance for oxygen evolution reaction (OER) in alkaline medium. As‐synthesized mesoporous ternary nitride NiCo2N shows desirable performance with very low overpotential (289 mV), and yields ≈10 mA cm−2 geometric current density. This is lower than the values of IrO2 and that of mesoporous binary nitrides CoN and Ni3N electrocatalysts. NiCo2N shows a small Tafel slope and smallest semicircle. Moreover, as‐synthesized NiCo2N exhibits low loss of activity after 10 h test for OER in alkaline solution. This work explores a promising way to produce OER electrocatalyst Co–Ni‐based ternary nitrides for water splitting applications.

HIGHLIGHTS• 3D mesoporous Ni 3 FeN was constructed through hard templating and thermal nitridation.• Ni 3 FeN exhibits superior electrochemical performance for OER with a small overpotential of 259 mV to achieve a 10 mA cm −2 .• Ni 3 FeN can also deliver a lower charging voltage and longer lifetime than RuO 2 in a rechargeable Zn-air battery.ABSTRACT As sustainable energy becomes a major concern for modern society, renewable and clean energy systems need highly active, stable, and low-cost catalysts for the oxygen evolution reaction (OER). Mesoporous materials offer an attractive route for generating efficient electrocatalysts with high mass transport capabilities. Herein, we report an efficient hard templating pathway to design and synthesize three-dimensional (3-D) mesoporous ternary nickel iron nitride (Ni 3 FeN). The as-synthesized electrocatalyst shows good OER performance in an alkaline solution with low overpotential (259 mV) and a small Tafel slope (54 mV dec −1 ), giving superior performance to IrO 2 and RuO 2 catalysts. The highly active contact area, the hierarchical porosity, and the synergistic effect of bimetal atoms contributed to the improved electrocatalytic performance toward OER.In a practical rechargeable Zn-air battery, mesoporous Ni 3 FeN is also shown to deliver a lower charging voltage and longer lifetime than RuO 2 . This work opens up a new promising approach to synthesize active OER electrocatalysts for energy-related devices.

Highly efficient electrocatalysts for oxygen evolution (OER) and hydrogen evolution reactions (HER) are critical in the development of efficient and sustainable alternative energy. Toward this goal, we report on the nanocasting synthesis of a three-dimensionally (3D) mesoporous CoP/CoCr2O4 heterojunction as efficient bifunctional electrodes for use in overall water splitting in alkaline media. The phosphorization of mesoporous Co2CrO4 nanocast from a KIT-6 hard silica template leads to phase transformation and separation, spontaneously forming a heterojunction between CoP and spinel CoCr2O4 with attractive nanostructured properties (large surface area of 83 m2/g with 4.8 nm diameter accessible mesopores). This phosphide–spinel oxide heterojunction catalyst yields excellent catalytic activity for both OER and HER with overpotentials of only 290 and 212 mV, respectively, to achieve the benchmark current density of 10 mA cm–2 in a 1.0 M KOH electrolyte. Moreover, CoP/CoCr2O4 shows small Tafel slopes with outstanding durability and long-life stability in alkaline media. Finally, the bifunctionality of CoP/CoCr2O4 for both OER and HER was shown by producing symmetric electrodes in an alkaline water electrolyzer, resulting in a low cell voltage of 1.68 V with 24 h durability, making it among the best Co-based electrocatalysts for overall water splitting. Such bifunctionality suggests a cost-effective heterojunction-based system for water electrolysis using inexpensive earth-abundant metals. The simple route to achieving an effective bifunctional material, which can be applied to various transition-metal-based homo- or heterojunctions, offers a paradigm for templated bifunctional electrode materials.

Prussian blue derived Fe2N nanoparticles to efficiently improve the photocatalytic H2-generation rate over pure g-C3N4 nanosheets.

A new means of producing MOF derived TMN materials, which in conjunction with suitable dyes, offer high-efficiency and low-cost avenues for making photocatalysts for hydrogen production.

Difluoro(methylene)cyclopropanes (F2MCPs) were prepared directly by difluorocarbene addition to allenes, and the resulting F2MCPs were converted into a variety of difluoro(methylene)cyclopropane derivatives through Heck reactions and electrophilic substitutions. The ring‐opening reactions of F2MCPs with I2 are reported and a plausible reaction mechanism is also discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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