Heteroatom Modification of Nanoporous Nickel Surfaces for Electrocatalytic Water Splitting

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.