Electronic modulation of Co2P nanoneedle arrays by the doping of transition metal Cr atoms for a urea oxidation reaction

Abstract

Urea electrolysis is of great interest for energy-related applications, but it is limited by a complex six-electron transfer process with slow kinetics. Herein, the in situ growth of Cr-doped Co₂P homogeneous nanoneedle arrays on nickel foam substrates (Cr-Co₂P/NF) was reported for the first time by a typical hydrothermal and low-temperature phosphorization process. The appropriate amount of Cr doping was found to promote the electronic modulation of active centers and the expansion of the specific active surface area, resulting in the superior performance of the urea oxidation reaction (UOR). It is noteworthy that Cr_0.4-Co₂P/NF exhibited a superior performance of the UOR at an onset potential of 1.290 V and a cell voltage of 1.333 V at 50 mA cm⁻² in 1 M KOH containing 0.5 M urea, which is one of the best catalytic activities reported so far. The experimental results demonstrate that the enhanced catalytic activity can be attributed to favorable electronic regulation, an improved charge transfer rate and increased exposure to active sites. Density functional theory (DFT) calculation indicates that the appropriate doping of Cr effectively regulates and controls the adsorption energy of urea and the conductivity of the Co₂P material itself. This work provides new ideas for the development of robust catalysts for the electrolysis of urea through doping strategies.