Simultaneous electrocatalytic hydrogen production and hydrazine removal from acidic waste water

This work reports a strategy of replacing the traditional oxygen evolution reaction with hydrazine oxidation reaction for hydrogen production in acidic media. The as-prepared PtCo alloy electrocatalyst can not only remarkably reduce the energy input for hydrogen production with an outstanding stability, but also efficiently decontaminate hydrazine effluent with a hydrazine removal efficiency up to 100%. • A proton exchange membrane hydrazine electrolyzer (PEMHE) design was developed for hydrogen production in acidic media. • PtCo alloy electrocatalysts can reduce the energy input for hydrazine assisted water splitting with an outstanding stability of over 3000 h in acidic media. • Proton exchange membrane hydrazine electrolyzer can achieve the mass hydrogen production under 100 mA cm −2 for at least 60 h. • Proton exchange membrane hydrazine electrolyzer can decontaminate hydrazine sewage with removal efficiency up to 100%. The application of proton exchange membrane water electrolyzer (PEMWE) technology has long been limited by the excessive energy consumption and poor catalyst durability because of the harsh corrosive and oxidative conditions that are related to the anodic oxygen evolution reaction (OER) in acidic electrolytes. Herein, we circumvent this challenge by adopting alternative hydrazine oxidation reaction (HzOR) as the anodic half-reaction, integrated with the cathodic hydrogen evolution reaction (HER) for sustainable hydrogen production. To this end, we further developed a PtCo alloy nanosheets electrocatalyst that can efficiently catalyze both the HzOR and HER with ultralow potentials. Specifically, the overall hydrazine splitting driven by the PtCo alloy requires only 0.28 V at 10 mA cm −2 along with outstanding stability of more than 3000 h. We further proposed a PEM hydrazine electrolyzer (PEMHE) design to promote the practical application. The device can not only produce hydrogen with a high yield rate of 1.87 mmol h −1 cm −2 at a practical current density of 100 mA cm −2 with a long durability of 60 h, but also effectively decontaminate hydrazine sewage with the hydrazine removal efficiency up to 100%. Our work provides a new solution to simultaneous mass hydrogen fuel production and hydrazine hazard removal from acidic waste water at minimized energy consumption.