Highly active non-noble electrocatalyst from Co2P/Ni2P nanohybrids for pH-universal hydrogen evolution reaction

Abstract

Many water sources including seawater, industrial wastewater and residential water are naturally promising ingredients for hydrogen production from water electrolysis, in which an efficient hydrogen-evolving electrocatalyst is required to work energetically under different pH environments. However, very few of non-noble electrocatalysts exhibit promising hydrogen-evolving activities in both neutral and alkaline solutions at present. Here we demonstrate that a highly porous hydrogen-evolving electrocatalyst, which is established by in-situ formation of Co2P/Ni2P nanohybrids with a nanometer size on a conductive CoNi foam, presents very outstanding pH-universal catalytic activities for hydrogen evolution in a wide pH range demanding extremely low overpotentials of 65.7 and 51 mV to yield 10 mA/cm2 with exceptionally operational durability in 1 M phosphate buffer solution (PBS, pH ≈ 6.5) and 1 M KOH (pH = 14), respectively, and 46 mV to deliver 20 mA/cm2 stably in 0.5 M H2SO4 (pH ≈ 0.3). More interestingly, it is worth mentioning that this catalyst can bear huge current densities up to 177, 1700 and 1000 mA/cm2 once the overpotential is increased to 0.2 V in neutral, alkaline and acidic solutions, respectively. These catalytic activities outperform most of the documented non-noble electrocatalysts composed of transition metal phosphides, selenides, sulfides, etc., and match or even surpass noble Pt catalysts. It probably represents the best hydrogen-evolving activity among the ever-reported Earth-abundant catalysts for HER hitherto, which is probably arisen from the large surface area, the exposure of numerous active sites and strong interfacial interactions between Co2P and Ni2P particles. This discovery may pave a new avenue toward the development of robust inexpensive electrocatalysts for hydrogen production in unfavorable neutral or alkaline media.