Carbon‐Oxyanion Atomically Steering Direct Urea Oxidation on NiOOH at Industrial Current Densities
Liqiang Hou, Chaoyue Sun, Zhaoyue Zhang, Haeseong Jang, Zijian Li, Min Gyu Kim, Jaephil Cho, Shangguo Liu, Xien Liu
Abstract
Abstract Developing cost‐effective electrocatalysts for the urea oxidation reaction (UOR) requires overcoming fundamental limitations of Ni‐based systems: sluggish Ni 2+ /Ni 3+ redox kinetics, competing oxygen evolution, and structural instability. Herein, we demonstrate an organic acid‐assisted electrochemical reconstruction strategy to synthesize carbon‐based oxyanion atomically modified β‐NiOOH nanosheets (Activated NiC 2 O 4 /NF) from nickel oxalate precursors. The in situ embedded oxyanions (‐CO x ) confer triple functionality: 1) enabling direct urea oxidation at ultralow potentials (1.253 V@10 mA cm −2 , 1.357 V@2000 mA cm −2 in 6 m KOH + 0.33 m urea) bypassing NiOOH pre‐formation; 2) suppressing competing OER via a 0.23 eV thermodynamic penalty on the deprotonation evolution step; 3) enhancing lattice oxygen stability by increasing the oxygen vacancy formation energy. This synergy delivers record stability (3000 h@100 mA cm −2 ) and near‐unity N‐product selectivity (>95 ± 2% Faradaic efficiency). In a practical alkaline urea electrolyzer (6 m KOH + 0.33 M urea, 80 °C), it achieves 2000 mA cm −2 at 2.089 V, surpassing state‐of‐the‐art systems. Operando studies and DFT calculations reveal that in situ‐generated oxyanions not only promote UOR via an NH 3 intermediate‐assisted pathway but also inhibit the oxygen evolution reaction by suppressing deprotonation evolution at the active sites. This work establishes a paradigm for anionic‐modification engineering in high‐current‐density electrocatalysis.