Electrocatalytic Hydrogen Evolution in Neutral pH Solutions: Dual-Phase Synergy

Abstract

Electrolysis in neutral pH solutions (e.g., wastewater and seawater) presents a transformative way for environmentally friendly, cost-effective hydrogen production. However, one of the biggest challenges is the lack of active, robust hydrogen evolution reaction (HER) catalysts. In this work, we present a catalyst with dual-active sites of MoP<sub>2</sub> and MoP, which function synergistically to promote HER in neutral pH solutions. In our microbial electrolysis cell (MEC) test, which uses neutral pH wastewater as feedstock, this catalyst delivers an average HER current density of 157 A m<sup>–2</sup><sub>cathode-surface-area</sub>, higher than Pt catalyst (145 A m<sup>–2</sup><sub>cathode-surface-area</sub>)—with the same amount of catalyst loading, ~5 times higher than the state-of-art Pt group metal-free catalysts in MECs. Our catalyst also outperforms Pt in natural seawater with ~10% higher and more stable HER current density. The fundamental reason for the enhanced HER performance is identified to be the synergy between MoP2 and MoP phases, with MoP<sub>2</sub> promoting H<sub>2</sub>O dissociation and MoP efficiently converting H<sub>ad</sub> into H<sub>2</sub>.