• • The optimal Cu/WO3 heterojunction delivers an ammonia yield rate of 158.66 μmol h−1 cm−2 and a Faradaic efficiency of 98.27%, exceeding typical monometallic Cu benchmarks by a substantial margin; this performance directly addresses the industrial requirement for high-current-density NRA electrolyzers where HER competition otherwise erodes ammonia selectivity.
• • Carbothermal shock reduction achieves ultra-high temperatures in short bursts, preventing active-site accumulation and yielding highly dispersed Cu/WO3 heterojunctions; this synthesis route is compatible with roll-to-roll carbon fiber processing, offering a scalable pathway to electrode fabrication without precious-metal loadings.
• • EPR and DFT calculations confirm that WO3 sites accelerate water dissociation to generate hydrogen radicals (H*), while Cu sites selectively adsorb NO3−; this spatial separation of functions suppresses HER and enables a low-overpotential hydrogen radical-mediated pathway, which is critical for reducing energy consumption in electrochemical ammonia production.
• • The heterojunction design eliminates the rate-determining step bottleneck of nitrate-to-nitrite conversion on monometallic Cu, where satisfactory NH3 yield and Faradaic efficiency are otherwise achieved only at high overpotentials with inevitable HER; the demonstrated 98.27% Faradaic efficiency at the reported yield rate indicates that parasitic HER current is largely eliminated under optimized conditions.