Ultralow-voltage hydrogen production and simultaneous Rhodamine B beneficiation in neutral wastewater

Electrocatalytic water splitting for hydrogen production is hampered by the sluggish oxygen evolution reaction (OER) and large power consumption and replacing the OER with thermodynamically favourable reactions can improve the energy conversion efficiency. Since iron corrodes easily and even self-corrodes to form magnetic iron oxide species and generate corrosion currents, a novel strategy to integrate the hydrogen evolution reaction (HER) with waste Fe upgrading reaction (FUR) is proposed and demonstrated for energy-efficient hydrogen production in neutral media. The heterostructured MoSe₂/MoO₂ grown on carbon cloth (MSM/CC) shows superior HER performance to that of commercial Pt/C at high current densities. By replacing conventional OER with FUR, the potential required to afford the anodic current density of 10 mA cm⁻² decreases by 95%. The HER/FUR overall reaction shows an ultralow voltage of 0.68 V for 10 mA cm⁻² with a power equivalent of 2.69 kWh per m³ H₂. Additionally, the Fe species formed at the anode extract the Rhodamine B (RhB) pollutant by flocculation and also produce nanosized magnetic powder and beneficiated RhB for value-adding applications. This work demonstrates both energy-saving hydrogen production and pollutant recycling without carbon emission by a single system and reveals a new direction to integrate hydrogen production with environmental recovery to achieve carbon neutrality. © 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences