Intermetallic Single-Atom Alloy In–Pd Bimetallene for Neutral Electrosynthesis of Ammonia from Nitrate

Harvesting recyclable ammonia (NH3) from the electrocatalytic reduction of nitrate (NO3RR) offers a sustainable strategy to close the ecological nitrogen cycle from nitration contamination in an energy-efficient and environmentally friendly manner. The emerging intermetallic single-atom alloys (ISAAs) are recognized to achieve the highest site density of single atoms by isolating contiguous metal atoms into single sites stabilized by another metal within the intermetallic structure, which holds promise to couple the catalytic benefits from intermetallic nanocrystals and single-atom catalysts for promoting NO3RR. Herein, ISAA In–Pd bimetallene, in which the Pd single atoms are isolated by surrounding In atoms, is reported to boost neutral NO3RR with a NH3 Faradaic efficiency (FE) of 87.2%, a yield rate of 28.06 mg h–1 mgPd–1, and an exceptional electrocatalytic stability with increased activity/selectivity over 100 h and 20 cycles. The ISAA structure induces substantially diminished overlap of Pd d-orbitals and narrowed p–d hybridization of In-p and Pd-d states around the Fermi level, resulting in a stronger NO3– adsorption and a depressed energy barrier of the potential-determining step for NO3RR. Further integrating the NO3RR catalyst into a Zn–NO3– flow battery as the cathode delivers a power density of 12.64 mW cm–2 and a FE of 93.4% for NH3 production.