Edge and defect sites in porous activated coke enable highly efficient carbon-assisted water electrolysis for energy-saving hydrogen production

Developing energy-efficient water electrolysis (WE) process is critical to the mass production of H₂. As the theoretical thermodynamics potential for carbon oxidation into CO₂ is 0.21 V, the introduction of carbon is possible to reduce the power consumption for WE to 1/6. Herein, we adopt three kinds of microporous activated coke to study the electrochemical carbon oxidation reaction (ECOR) properties. Experimental and computational results demonstrate that carbon atoms located at edges and defects could be active sites in ECOR, whereas C[dbnd]O groups generated after electro-oxidized inhibit the process of ECOR. Additionally, a new Fe(II)/Fe(III) redox-coupled hydrogen evolution reaction system is designed for WE. The assembled electrolyzer only requires a voltage of 1.2 V to achieve a current density of 97 mA cm⁻² without any metal catalyst at the anode and the corresponding electricity consumption is 2.87 kWh Nm⁻³ (H₂). These findings provide a promising strategy for low-cost, efficient H₂ production.