Strong electronic coupling of CoNi and N-doped-carbon for efficient urea-assisted H2 production at a large current density

Abstract

Exploiting efficient urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) catalysts are significant for energy-saving H2 production through urea-assisted water electrolysis, but it is still challenging. Herein, carbon-encapsulated CoNi coupled with CoNiMoO (CoNi@CN-CoNiMoO) is prepared by solvothermal method and calcination to enhance the activity/stability of urea-assisted water electrolysis at large current density. It exhibits good activity for UOR (E10/1,000 = 1.29/1.40 V) and HER (E−10/−1000 = −45/−245 mV) in 1.0 M KOH + 0.5 M urea solution. For the UOR||HER system, CoNi@CN-CoNiMoO only needs 1.58 V at 500 mA cm−2 and shows good stability. Density functional theory calculation suggests that the strong electronic interaction at the interface between NiCo alloy and N-doping-carbon layers can optimize the adsorption/desorption energy of UOR/HER intermediates and accelerate the water dissociation, which can expedite urea decomposition and Volmer step, thus increasing the UOR and HER activity, respectively. This work provides a new solution to design UOR/HER catalysts for H2 production through urea-assisted water electrolysis.