Cycad-leaf-like crystalline-amorphous heterostructures for efficient urea oxidation-assisted water splitting

Abstract

Developing efficient bifunctional catalysts for urea oxidation reaction (UOR)/hydrogen evolution reaction (HER) is important for energy-saving hydrogen production. Herein, a catalyst with crystalline-amorphous heterostructure supported by NiCo alloy on nickel foam (NiCoO-MoO_x/NC) is reported for the first time. Through simple molybdenum salt etching, 2D NiCo alloy nanosheets are transformed into a unique 3D cycad-leaf-like structure with a super-hydrophilic surface. Simultaneously, the synergistic effect between crystalline NiCoO and amorphous MoO_x improves the UOR and HER activity, merely requiring 1.28 V and −45 mV potentials to reach ±10 mA cm⁻², respectively. Particularly, the UOR kinetics of NiCoO-MoO_x/NC is enhanced significantly compared to that of NiCoO/NC. The electronic structure of NiCoO is modified by MoO_x, enabling the rapid generation of NiOOH and CoOOH active species, which would accelerate the synergistic electrocatalytic oxidation of urea molecules. This work inspires the design of highly active and stable bifunctional catalysts for urea assisted H₂ production.