Regulating the Electrochemical Nitrate Reduction Performance with Controllable Distribution of Unconventional Phase Copper on Alloy Nanostructures

Abstract Electrochemical nitrate reduction reaction (NO ₃ RR) is emerging as a promising strategy for nitrate removal and ammonia (NH ₃ ) production using renewable electricity. Although great progresses have been achieved, the crystal phase effect of electrocatalysts on NO ₃ RR remains rarely explored. Here, the epitaxial growth of unconventional 2H Cu on hexagonal close‐packed ( hcp ) IrNi template, resulting in the formation of three IrNiCu@Cu nanostructures, is reported. IrNiCu@Cu‐20 shows superior catalytic performance, with NH ₃ Faradaic efficiency (FE) of 86% at −0.1 (vs reversible hydrogen electrode [RHE]) and NH ₃ yield rate of 687.3 mmol g _Cu ⁻¹ h ⁻¹ , far better than common face‐centered cubic Cu. In sharp contrast, IrNiCu@Cu‐30 and IrNiCu@Cu‐50 covered by hcp Cu shell display high selectivity toward nitrite (NO ₂ ⁻ ), with NO ₂ ⁻ FE above 60% at 0.1 (vs RHE). Theoretical calculations have demonstrated that the IrNiCu@Cu‐20 has the optimal electronic structures for NO ₃ RR due to the highest d‐band center and strongest reaction trend with the lowest energy barriers. The high electroactivity of IrNiCu@Cu‐20 originates from the abundant low coordination of Cu sites on the surface, which guarantees the fast electron transfer to accelerate the intermediate conversions. This work provides a feasible tactic to regulate the product distribution of NO ₃ RR by crystal phase engineering of electrocatalysts.