Alloying of Cu with Ru Enabling the Relay Catalysis for Reduction of Nitrate to Ammonia

Abstract Involving eight electron transfer process and multiple intermediates of nitrate (NO 3 − ) reduction reaction leads to a sluggish kinetic and low Faradaic efficiency, therefore, it is essential to get an insight into the reaction mechanism to develop highly efficient electrocatalyst. Herein, a series of reduced‐graphene‐oxide‐supported RuCu alloy catalysts (Ru x Cu x /rGO) are fabricated and used for the direct reduction of NO 3 − to NH 3 . It is found that the Ru 1 Cu 10 /rGO shows the ammonia formation rate of 0.38 mmol cm −2 h −1 (loading 1 mg cm −2 ) and the ammonia Faradaic efficiency of 98% under an ultralow potential of −0.05 V versus Reversible Hydrogen Electode (RHE), which is comparable to Ru catalyst. The highly efficient activity of Ru 1 Cu 10 /rGO can be attributed to the synergetic effect between Ru and Cu sites via a relay catalysis, in which the Cu shows the exclusively efficient activity for the reduction of NO 3 − to NO 2 − and Ru exhibits the superior activity for NO 2 − to NH 3 . In addition, the doping of Ru into Cu tunes the d‐band center of alloy and effectively modulates the adsorption energy of the NO 3 − and NO 2 − , which promotes the direct reduction of NO 3 − to NH 3 . This synergetic electrocatalysis strategy opens a new avenue for developing highly efficient multifunctional catalysts.