Theoretical insights of nickel-based dual-metal atoms supported on C2N sheets for urea electrooxidation

Abstract

The electrocatalytic urea oxidation reaction (UOR) enables energy-saving hydrogen production and waste degradation but requires efficient catalysts due to its complex, sluggish 6-electron transfer mechanism. In this study, we designed a series of stable 3d transition metal heterometal atom pairs (TMNi, TM refers to Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, or Zn) supported on the C2N substrate as UOR catalysts, systematically investigating their potential to enhance the activity of Ni2/C2N. Among these, CrNi/C2N displayed a superior capability to lower the limiting potential of the UOR compared to CuNi/C2N and Ni/C2N. The enhanced catalytic CrNi/C2N system primarily stems from the stronger TM–Ni interactions, notable differences in charge distribution, more localized electronic states, and a higher d-band center associated with CrNi/C2N relative to CuNi/C2N and Ni2/C2N. These attributes not only ensure the stability of the well-dispersed CrNi pairs on C2N but also amplify the ability of the active center to adsorb and activate reaction intermediates. Moreover, CrNi/C2N demonstrates good selectivity for the UOR by exhibiting reduced susceptibility to forming NO2 by-products and undergoing the competing oxygen evolution reaction. This theoretically driven work identifies CrNi/C2N as the top-performing UOR dual-metal-atom catalysts, combining 0.99 V limiting potential with selective N2 generation through electronic structure modulation, offering guidance for advanced catalyst design through the strategic use of transition metal heterometal atom pairs. Keywords: Urea oxidation reaction; C2N; Dual-atom catalyst; Nickel-based compounds; DFT calculations.