Copper-based catalysts are widely regarded as promising candidates for electrocatalytic nitrate reduction (NO3RR), an environmentally benign route to ammonia synthesis, yet their efficiency is often constrained by nitrite accumulation and insufficient active hydrogen (*H) supply at high current densities. Here, isolated Cu atoms were anchored into a hollow Co3S4 polyhedral framework (Cu-Co3S4), generating a sulfur bridged asymmetric active center. Electrochemical and computational studies reveal that Co3S4 functions as an efficient *H donor, transferring hydrogen species to Cu sites through a sulfur bridge mediated reverse hydrogen spillover process, thereby accelerating the hydrogenation of nitrogen intermediates. By precisely tuning the Cu site density to balance nitrogen intermediate adsorption with *H supply, the optimized Cu1.01wt%-Co3S4 catalyst delivers an exceptional NH3 yield rate of 94.52 mg h-1 mgcat. -1 (18.90 mg h-1 cm-2) and a Faradaic efficiency (FE) of 95.18% at -0.8 V vs reversible hydrogen electrode. The catalyst also exhibits remarkable durability over 300 h at -200 mA cm-2 and performs effectively in zinc-nitrate batteries. These findings highlight the importance of coupling intermediate activation with hydrogenation kinetics and provide guiding principles for the rational design of high efficiency NO3RR electrocatalysts.
Li et al. (Wed,) studied this question.