Direct Electrolysis of Municipal Reclaimed Water for Efficient Hydrogen Production Using a Bifunctional Non-Noble-Metal Catalyst.

Water electrolysis for green H production traditionally requires a stable supply of renewable electricity and pure water. However, spatial separation of renewables and water resources as well as water scarcity per capita in China necessitate unconventional water resources for electrolysis. Reclaimed water produced from municipal wastewater treatment plants is widely distributed with quality improved significantly in recent years, which may be a promising alternative to feedstock. However, there are few reports on the direct use of this wastewater for H production. Here, we present a direct electrolysis of reclaimed water for decentralized H production by developing a highly efficient and stable bifunctional 3D-dandelion-like (DL) vanadium(V)-doped CoP catalyst grown on Ni foam (NF) in an alkaline electrolyzer. The V-CoP-DL/NF electrode decreases 6.5 and 25% overpotentials of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, compared to noble-metal Pt (HER) and IrO (OER) catalysts, and exhibits exceptional durability, as a voltage required for overall reclaimed water splitting only increases by 80 mV (1.81-1.89 V) after 90 days of operation at a current density of 10 mA cm. The maximum stable current can reach 1000 mA cm. The impacts of potential pollutants in reclaimed water on the performance of electrolysis and the behavior of major wastewater ions in alkaline electrolyte were investigated. The observed exceptional performance is attributed to the catalyst's unique nanostructure, which enhances charge transfer and reactant/electrolyte diffusion. The growth strategy further enhances the conductivity and stability of the catalyst. This work underscores the feasibility of utilizing reclaimed water instead of pure water as the feedstock for sustainable hydrogen production.