Modulating the proton transfer kinetics via Ru single atoms for highly efficient ammonia synthesis

The electrochemical nitrate reduction reaction (eNO3RR) is an appealing technology for converting environmentally toxic NO3− to ammonia (NH3). This approach was usually obstructed by the multi-proton/electron involved process. Here, we report a catalyst with Ru single atoms supported on Co3O4 (Ru SAs-Co3O4). The as-developed Ru SAs-Co3O4 catalyst shows a remarkable NH3-evolving activity with a faradic efficiency of 94.92% ± 4.02% at the potential of −0.2 V (vs. RHE) and a generation rate of 1,843.45 ± 57.14 μmol h−1 cm−2 at the potential of −0.5 V. Further investigations revealed that the Ru SAs play a dual role in simultaneously accelerating the proton transfer and modulating the d-electron structures of the neighboring Co sites, which led to a lower energy barrier of the rate-determining step. Eventually, by combining the eNO3RR and electrosynthesis of 5,5′-azotetrazolate at a two-electrode system, an energy-saving NH3 synthesis, while simultaneously producing value-added chemicals, was successfully achieved. [Display omitted] •A tandem catalyst with Ru single atoms supported on Co3O4 denoted as Ru SAs- Co3O4•The catalyst shows a high NH3 yield rate (1,843.45 μmol h−1 cm−2) and FE (94.92%)•Kinetic studies suggest Ru SAs could accelerate the proton transfer for boosting the eNO3RR Ammonia production by the electrochemical nitrate reduction reaction (eNO3RR) provides an intriguing approach for both environmental denitrification and sustainable fuel production. The eNO3RR involves multi-proton transfer steps, and the sequential generation and consumption of adsorbed hydrogen (Hads) is strongly relevant to the rate-determining step. Here, we report a tandem catalyst comprising Ru single atoms supported on Co3O4 (Ru SAs-Co3O4). The surface coverage of Hads on the catalyst was regulated by the loading of Ru SAs, thus simultaneously facilitating the reduction of nitrate and suppressing hydrogen evolution in the eNO3RR. Under optimized conditions, the Ru SAs-Co3O4 catalyst exhibited remarkable NH3-evolving activity. Further investigations revealed that Ru SAs play a dual role in accelerating the proton transfer and modulating the d-electron structures of the neighboring Co sites, collectively leading to a lower energy barrier of the rate-determining step. A novel catalyst composed of Ru single atoms (SAs) supported on Co3O4 was developed for efficient NO3− to NH3 conversion. The Ru SAs play a dual role in simultaneously accelerating the proton transfer and modul