Redistributing Interfacial Charge Density of Ni12p5/Ni3p Via Fe Doping for Ultrafast Urea Oxidation Catalysis at Large Current Densities

Abstract

Large-scale industrial application of urea electrolysis has prompted one to explore inexpensive and efficient urea oxidation reaction (UOR) catalysts that can achieve large current densities (≥ 500 mA cm-2) at relatively low potentials. In response, for the first time the robust UOR catalysts are developed via in-situ construction of the Fe-doped Ni12P5/Ni3P heterojunction nanosheets on the macroporous 3D NiFe foam skeleton (denoted as Fe-(Ni12P5/Ni3P)). The introduction of Fe element can not only strengthen the interfacial electric field and induce the spontaneous charge redistribution for heterogeneous Ni12P5/Ni3P, but also effectively lower the reaction energy barrier during stepwise UOR process. Benefiting from the unique ultra-thin nanosheets and the optimized electronic structure, the well-designed Fe-(Ni12P5/Ni3P) possesses more exposed active sites and faster electron and mass transfer, thus exhibiting superior catalytic UOR activity. Encouragingly, the Fe-(Ni12P5/Ni3P) can deliver the industrial-level current density of 800 mA cm-2 just at 1.4 V as well as a splendid Tafel slope of 28.2 mV dec-1. This catalyst also manifests remarkable durability under high current densities. As a consequence, our work opens up a brand-new-path in rational design of excellent UOR catalysts with high activity and stability to enable energy-saving electrolytic hydrogen production on industrial scale.

Keywords: Fe substitution, phosphide, Heterojunction, charge redistribution, Urea oxidation reaction