Local Charge Modulation Induced the Formation of High-Valent Nickel Sites for Enhanced Urea Electrolysis

초록

Ni-based electrocatalysts are considered to be significantly promising candidates for electrocatalytic urea oxidation reaction (UOR). However, their UOR activity and stability are severely enslaved by the inevitable Ni group self-oxidation phenomenon. In this study, the glassy state NiFe LDH with uniform Cu dopant (Cu-NiFe LDH) by a simple sol-gel strategy is successfully synthesized. When served as the UOR catalyst, Cu-NiFe LDH required a 123 mV lower potential for UOR at both 10 and 100 mA cm-2 in comparison with the conventional anodic OER. It can also operate steadily for more than 300 h at 10 mA cm-2. The in-depth investigation reveals that Cu incorporation can optimize the local electronic structure of Ni species to induce high-valent Ni sites. The high-valent Ni sites would act as the active center during the proposed energetically favorable UOR route, which directly reacts on the high-valent Ni sites without self-oxidation inducing the formation of NiOOH species, resulting in a boosted electrocatalytic UOR activity and stability. The Cu dopant regulates the local charge distribution of Ni atoms, leading to the formation of high-valent Ni sites with superior activity and thus accelerating the UOR kinetics. image

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