Artificial Heterointerfaces with Regulated Charge Distribution of Ni Active Sites for Urea Oxidation Reaction.

In contrast to the thermodynamically unfavorable anodic oxygen evolution reaction, the electrocatalytic urea oxidation reaction (UOR) presents a more favorable thermodynamic potential. However, the practical application of UOR has been hindered by sluggish kinetics. In this study, hierarchical porous nanosheet arrays featuring abundant Ni-WO 3 heterointerfaces on nickel foam (Ni-WO 3 /NF) is introduced as a monolith electrode, demonstrating exceptional activity and stability toward UOR. The Ni-WO 3 /NF catalyst exhibits unprecedentedly rapid UOR kinetics (200 mA cm -2 at 1.384 V vs. RHE) and a high turnover frequency (0.456 s -1 ), surpassing most previously reported Ni-based catalysts, with negligible activity decay observed during a durability test lasting 150 h. Ex situ X-ray photoelectron spectroscopy and density functional theory calculations elucidate that the WO 3 interface significantly modulates the local charge distribution of Ni species, facilitating the generation of Ni 3+ with optimal affinity for interacting with urea molecules and CO 2 intermediates at heterointerfaces during UOR. This mechanism accelerates the interfacial electrocatalytic kinetics. Additionally, in situ Fourier transform infrared spectroscopy provides deep insights into the substantial contribution of interfacial Ni-WO 3 sites to UOR electrocatalysis, unraveling the underlying molecular-level mechanisms. Finally, the study explores the application of a direct urea fuel cell to inspire future practical implementations.