Heteroatom Modification of Nanoporous Nickel Surfaces for Electrocatalytic Water Splitting
Jingjun Shen, Xingqun Zheng, Lishan Peng, Geoffrey I. N. Waterhouse, Lianqiao Tan, Jiao Yang, Li Li, Zidong Wei
Abstract
Herein, we report heteroatom (N and O)-modified nanoporous Ni surfaces on Ni foam (NF) as a high-performance bifunctional electrode for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysis. Briefly, a Ni(OH)2-decorated NF was prepared by a facile hydrothermal method, which was then subjected to thermal ammonoloysis at temperatures between 300 and 600 °C. The introduction of N atoms significantly modulates the electronic structure of metallic Ni and maintains metallic conductivity for both HER and OER electron-transfer processes. During the OER, a N,O comodified Ni surface is formed in situ, resulting in an optimized Gibbs free energy for the potential-determining step (ΔGpds) of the OER. The compositionally optimized Ni/Ni-N0.28/NF electrode requires a low overpotential of only 63 mV at 10 mA cm–2 for the HER and 320 mV at 20 mA cm–2 for the OER. A water electrolyzer constructed using Ni/Ni-N0.28/NF as the HER and OER electrodes offered excellent performance and durability, outperforming devices based on Pt/C and RuO2 catalysts. The influence of modulation and coverage of the N atom on the HER performance of Ni/Ni-Nn was probed by DFT calculation, with the in situ formation of N, O comodified nanoporous Ni surfaces underpinning the outstanding OER activity of the Ni/Ni-Nn/NF electrodes.