Highly Mesoporous Cobalt-Hybridized 2D Cu₃P Nanosheet Arrays as Boosting Janus Electrocatalysts for Water Splitting

Recently, developing economical electrocatalysts with high performance in water decomposition has become a research hotspot. Herein, two kinds of cobalt-hybridized Cu₃P nanostructure array electrocatalysts (including highly mesoporous 2D nanosheets and sugar gourd-like 1D nanowires) were controllably grown on a nickel foam substrate through a simple hydrothermal method combined with a subsequent phosphating treatment method. An electrocatalytic test indicated that the as-prepared 2D nanosheet array exhibited excellent activity and stability toward hydrogen evolution reaction under alkaline conditions, which offered a low overpotential of 99 mV at 10 mA/cm² and a small Tafel slope of 70.4 mV/dec, whereas a competitive overpotential of 272 mV was required for oxygen evolution reaction. In addition, the 2D nanosheet array delivered a low cell voltage of 1.66 V at 10 mA/cm² in a symmetric two-electrode system, implying its huge potential in overall water decomposition. The electrocatalytic performance is superior to the as-prepared 1D nanowire array and most of the Cu₃P-related electrocatalysts previously reported. Experimental measurements and first-principles calculations show that the excellent performance of the 2D nanosheet array can be attributed to its unique 2D mesoporous structure and hybridization of cobalt, which not only provide a large electrochemically active surface and fast electrocatalytic reaction kinetics but also weaken the binding strength of electrocatalytic reaction intermediates. The present study provides a simple and controllable approach to synthesize Cu₃P-based bimetallic phosphide nanostructures, which can be used as boosting Janus electrocatalysts for water decomposition.