Large-Current CO₂ Electromethanation Through Active Hydrogen Regulation Over Carbon Nitride

Electromethanation of CO₂ has received intensive attention due to its high calorific value and convenient storage along with transportation to accommodate industrial demands. However, it is limited by sluggish multi-step proton-coupled electron transfer kinetics and undesired ^*H coupling under high current density, posing great challenges to its commercialization. Herein, carbon nitride (CN) with superior hydrogen adsorption ability is used as an active-hydrogen adsorption and supply material. Through a facile liquid-assisted exfoliation and electrostatic self-assembly strategy to strengthen its interfacial contacts with Cu₂O catalysts, yielding a strengthened CH₄ production 52 times higher than that of pristine Cu₂O. Flow-cell test ultimately achieved FE_CH4 and remarkably CH₄ partial current density of 61% and 561 mA cm^-2, respectively. With in situ ATR-FTIR spectra and DFT calculations, it is established that strengthened interfaces enabled abundant ^*H tethered by ─C─N═C─ sites in CN nanosheets and oriented to the ^*CO hydrogenation to ^*CHO and ^*CHx on Cu species. This work reveals the profound influence of fine-expanded interfaces with dimensional materials on the product distribution and yield through the active-hydrogen management, which is of reference value for other small-molecule electro-polarization dominated by the proton-coupled electron transfer (PCET) process (e.g., N₂, O₂, etc.).