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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.

Transition metal borides are considered as promising electrocatalysts for water splitting due to their metallic conductivity and good durability. However, the currently reported monometallic and noncrystalline multimetallic borides only show generic and monofunctional catalytic activity. In this work, the authors design and successfully synthesize highly crystalline ternary borides, Mo2NiB2, via a facile solid‐state reaction from pure elemental powders. The as‐synthesized Mo2NiB2 exhibits very low overpotentials for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), that is, 280 and 160 mV to reach a current density of 10 mA cm−2, in alkaline media. These values are much lower from the ones observed over monometallic borides, that is, Ni2B and MoB, and the lowest among all nonprecious metal borides. By loading Mo2NiB2 onto Ni foams as both cathode and anode electrode for overall water splitting applications, a low cell voltage of 1.57 V is required to achieve a current density of 10 mA cm−2, comparable with the value required from the Pt/C||IrO2/C couple (1.56 V). The proposed synthesis strategy can be used for the preparation of cost‐effective, multi‐metallic crystalline borides, as multifunctional electrocatalysts.

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