Hierarchical superhydrophilic/superaerophobic CoMnP/Ni2P nanosheet-based microplate arrays for enhanced overall water splitting

Abstract

The development of efficient and stable non-noble metal bifunctional electrocatalysts for overall water splitting in acidic and alkaline media is highly desirable for industrial water electrolysis, but remains a profound challenge. Herein, for the first time, we report a general urea-modulated hydrothermal phosphorization strategy to directly grow hierarchical CoMnP/Ni₂P nanosheet-based microplate arrays on Ni foam (NF). Thanks to the unique hierarchical structure, CoP–MnP synergism, and superhydrophilicity and superaerophobicity of the CoMnP/Ni₂P/NF arrays, the optimized CoMnP/Ni₂P/NF shows high activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with low overpotentials in 0.5 M H₂SO₄ (HER: 84 mV; OER: 165 mV) and 1 M KOH (HER: 108 mV; OER: 209 mV) at a current density of 10 mA cm⁻², outperforming most of the reported electrocatalysts. Moreover, the assembled two-electrode electrolyzer with CoMnP/Ni₂P/NF as both the anode and cathode delivers a low cell voltage of 1.54 V at 10 mA cm⁻² with robust stability in alkaline electrolyte. More importantly, highly active and stable overall water splitting in acidic medium on a non-noble bifunctional electrocatalyst is realized, and only 1.43 V cell voltage is required to achieve 10 mA cm⁻² current density. This work not only creates an excellent non-noble bifunctional electrocatalyst for overall water splitting in acidic and alkaline media, but also provides a universal and practical way to prepare other nanostructured metal phosphides for diverse electrocatalytic reactions.