Active Site Tailoring of Ni‐Based Coordination Polymers for High‐Efficiency Dual‐Functional HER and UOR Catalysis

Abstract

AbstractNi‐based electrocatalysts are regarded as highly promising ones for urea‐assisted electrolytic water hydrogen production technology. However, during the urea oxidation reaction (UOR) process, their activity is significantly constrained by the unavoidable Ni species self‐oxidation reaction, and the harmful liquid‐phase products (NOx−) generated from over‐oxidize urea are also often neglected. Herein, A self‐supported W‐doped Ni‐C3S3N3‐based coordination polymer electrode (W‐NT@NF) with tailored Ni3+ active sites using ligand anchoring and high‐valence metal doping strategies is synthesized, which is certified that this pyrolysis‐free catalyst achieves dual‐functional hydrogen evolution reaction (HER) and UOR performance comparable to reported noble metal/non‐noble metal catalysts, both achieving high current densities approaching 1000 mA cm−2. Density functional theory (DFT) calculations, combined with spectroscopic characterizations that record the dynamic evolution of the catalyst during UOR and oxygen evolution reaction (OER) processes, reveal that the novel and energetically favorable UOR pathway is proposed, which initiates directly by the Ni3+ sites without self‐oxidation and involve the participation of the reconstructed NiOOH species resulting from OER. A combination of in‐line gas chromatography, and ion chromatography analysis indicates that the Faradaic efficiency (FE) of N2 is higher (34%) at lower current densities (<100 mA cm−2), and the FE of NOx− remains below 20% in long‐term electrolysis.