Heterostructure between super-aerophobic phosphate coatings and molybdate hydrate electrode for efficient urea electrolysis and hydrogen production

Abstract

Urea electrolysis can replace water electrolysis as the anode reaction, reducing the voltage required for hydrogen production and mitigating urea-induced environmental pollution. In this work, we synthesized NMOH (NiMoO₄·xH₂O) nanorod arrays on nickel foam (NF) via a hydrothermal method and then constructed an NMOH@Pi heterostructure through high-temperature phosphating, where Pi represented phosphate components of the shell. The heterointerface between NMOH and Pi enhances electronic interactions, improving electrical conductivity, intermediate adsorption, and reaction kinetics. Additionally, the super-hydrophilicity and super-aerophobicity of NMOH@Pi/NF enhance electrolyte immersion and bubble detachment, promoting mass transport. The Ni active sites are modulated by Mo, P, and O atoms, preventing further oxidation of Ni²⁺ during urea oxidation. Phosphorus doping stabilizes oxygen vacancies (Ov), improving catalytic performance. By the aid of the above designed favorable factors, the NMOH@Pi/NF catalyst achieves UOR and HER current densities of 100 mA cm⁻² at only 1.410 and 0.176 V, respectively. This work provides new insights for designing bimetallic or multimetallic synergistic electrocatalysts.