All-non-noble metal alkaline-based water electrolysis with NiFeP bamboo-like cathode

Abstract

Climate change and environmental concerns have driven restrictions on fossil fuel usage and increased the focus on green hydrogen as a clean energy carrier. Herein, we report a bamboo-like unified electrode composed of nickel-iron phosphide (UE-NiFeP) as a hydrogen evolution reaction (HER) catalyst for the alkaline water electrolyzer (AWE) and the anion-exchange membrane water electrolyzer (AEMWE). The NiFeP unified electrode (UE-NiFeP) exhibited bamboo-like structures with periodic ridges, resulting in higher HER activity and stability than the NiFeOx unified electrode (UE-NiFeOx) and the conventional NiFeOx electrode (CE-NiFeOx). Density functional theory (DFT) simulations further confirmed the superior HER performance of UE-NiFeP by showing that phosphidation optimizes the adsorption strength of HER intermediates. After its application in practical AWE and AEMWE, the performance of UE-NiFeP were superior to those with UE-NiFeOx and CE-NiFeOx, achieving a current density of 1947 mA cm-2 at 1.9 V under AEMWE conditions. When compared with those of AEMWE with non-noble metal OER and HER catalysts, this performance is among the top-performing systems reported to date, thereby enabling the production of low-cost green hydrogen. Additionally, the AEMWE performance with UE-NiFeP was durable without significant degradation for 350 h under a constant current density of 1000 mA cm-2. Furthermore, the excellent performance of the single cell with UE-NiFeP was also retained in a 5-layer AEMWE stack configuration.