Phosphorus-doping promotes the electrochemical etching of metals to nanoporous electrodes for efficient and durable overall water splitting

Ruohan Feng ^a , Zhenhua Ye ^b , Qu Jiang ^a , Chuanwei Li ^b,**, Jianfeng Gu ^b , Fang Song ^a,*

a State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China

b Institute of Materials Modification and Modelling, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China

Abstract

Electrocatalysts play a central role in electrochemical water splitting to store renewable energy in the chemical fuel of hydrogen. Nanoporous metal electrodes are promising to boost hydrogen production efficiency while challenging in synthesis. Here, a phosphorus-doping assisted electrochemical etching strategy is developed to construct highly nanoporous surfaces on metal electrodes, leading to a remarkable catalytic performance for overall water splitting under lab-level or industrial electrolysis conditions. Specifically, the nanoporous FeCoNiCu foil shows 46 times higher electrochemical surface area, lowering the overpotentials by 102 mV for oxygen evolution reaction and 157 mV for hydrogen evolution reaction. The viability of the strategy is further demonstrated in the prevailing industrial electrodes of nickel meshes, enabling a cell voltage of only 1.931 V under the harsh industrial electrolytic condition (80 ◦C, 30 wt% KOH, and a current density of 500 mA cm− 2 ). It is 126 mV lower than that of a bare nickel mesh-based electrolyzer and corresponds to a ~4% improvement in energy-conversion efficiency. This work offers a facile and ease-to-scale-up approach for the upgrading of widespread metal electrodes, possessing great prospects in energy conversion and storage devices including electrolyzers, fuel cells, batteries, and supercapacitors.