Electrocatalytic nitrate reduction reaction (NO3RR) is of great significance for wastewater remediation and ammonia (NH3) synthesis. However, efficient NO3RR catalysts and a clear mechanistic understanding are still lacking. Single-atom alloy (SAA) offers a new design space for NO3RR with its unique atomic and electronic structures. Here, high-throughput density functional theory (DFT) calculations were performed to systematically investigate the catalytic potential and reaction mechanism of Cu-based SAAs for NO3RR to NH3. A volcano relationship between the descriptor ∆E*NO − ∆E*OH and the limiting potential (UL) was established. The results show that Al/Cu (111) achieves an ultra-low UL of −0.18 V. The strong hybridization between Al-p and O-p orbitals enables p electrons to be injected more readily into anti-bonding orbitals, thereby effectively weakening N-O bond and lowering the reaction energies of protonation steps. The stronger O affinity of Al site allows Al/Cu (111) to break free from the constraints imposed by conventional linear scaling relations and exhibit excellent NO3RR activity. Moreover, Al/Cu (111) protects the active sites from competitive H adsorption, leading to enhanced selectivity. This work establishes p-orbital engineering as a design principle for Cu-based single-atom alloys beyond conventional d-band tuning, providing valuable theoretical guidance for NO3RR catalyst design.
