Atomic Hydrogen Mediated Efficient Electrocatalytic Hydrogenation Reactions

Abstract Although atomic hydrogen (H * ) is a crucial active species during the electrocatalytic hydrogenation process, its excessive production accelerates its self‐quenching into hydrogen (H 2 ), which decreases the reduction efficiency of the target reactant and causes cathode instability. Herein, a universal strategy is proposed to enhance the efficiency of diverse electrocatalytic hydrogenation reactions (such as cyanide (CN − ), nitrate (NO 3 − ), carbon dioxide (CO 2 ), or oxygen (O 2 ) reductions) based on the supply‐demand balance of H * . Through passivating the terminal oxygen sites with unsaturated coordination in Co 3 O 4 with grafted sulfur (Co 3 O 4 ‐S), the free energy for H * generation increases from 0.17 to 0.41 eV, efficiently regulating its production rate to restrain its excess formation. The supply‐demand balance of H * promotes its utilization and suppresses HER, immensely improving the deep hydrogenation of CN − (Faraday efficiency (FE ch 4 /nh 3 /ch 3 nh 2 ): 19.6% → 45.3%), NO 3 − (FE nh 3 : 83% → 100%), CO 2 (FE CO : 25.1% → 51.7%) and O 2 (transferred electrons: 2.6 → 3.6). This electrocatalytic system also exhibits excellent practical application potential, such as the cyanide‐containing wastewater treatment. This work offers a new idea to enhance the utilization efficiency of cathodic active species for electrocatalytic reduction reactions and provides technical support for the design and synthesis of highly efficient and stable electrode materials.