RESUMO
The electrocatalytic conversion of nitrate (NO3 - ) to NH3 (NO3 RR) at ambient conditions offers a promising alternative to the Haber-Bosch process. The pivotal factors in optimizing the proficient conversion of NO3 - into NH3 include enhancing the adsorption capabilities of the intermediates on the catalyst surface and expediting the hydrogenation steps. Herein, the Cu/Cu2 O/Pi NWs catalyst is designed based on the directed-evolution strategy to achieve an efficient reduction of NO3 â¾. Benefiting from the synergistic effect of the OV -enriched Cu2 O phase developed during the directed-evolution process and the pristine Cu phase, the catalyst exhibits improved adsorption performance for diverse NO3 RR intermediates. Additionally, the phosphate group anchored on the catalyst's surface during the directed-evolution process facilitates water electrolysis, thereby generating Hads on the catalyst surface and promoting the hydrogenation step of NO3 RR. As a result, the Cu/Cu2 O/Pi NWs catalyst shows an excellent FE for NH3 (96.6%) and super-high NH3 yield rate of 1.2 mol h-1 gcat. -1 in 1 m KOH and 0.1 m KNO3 solution at -0.5 V versus RHE. Moreover, the catalyst's stability is enhanced by the stabilizing influence of the phosphate group on the Cu2 O phase. This work highlights the promise of a directed-evolution approach in designing catalysts for NO3 RR.
RESUMO
The electrocatalytic conversion of nitrate (NO3 â¾) to NH3 (NO3 RR) offers a promising alternative to the Haber-Bosch process. However, the overall kinetic rate of NO3 RR is plagued by the complex proton-assisted multiple-electron transfer process. Herein, Ag/Co3 O4 /CoOOH nanowires (i-Ag/Co3 O4 NWs) tandem catalyst is designed to optimize the kinetic rate of intermediate reaction for NO3 RR simultaneously. The authors proved that NO3 â¾ ions are reduced to NO2 â¾ preferentially on Ag phases and then NO2 â¾ to NO on Co3 O4 phases. The CoOOH phases catalyze NO reduction to NH3 via NH2 OH intermediate. This unique catalyst efficiently converts NO3 â¾ to NH3 through a triple reaction with a high Faradaic efficiency (FE) of 94.3% and a high NH3 yield rate of 253.7 µmol h-1 cm-2 in 1 M KOH and 0.1 M KNO3 solution at -0.25 V versus RHE. The kinetic studies demonstrate that converting NH2 OH into NH3 is the rate-determining step (RDS) with an energy barrier of 0.151 eV over i-Ag/Co3 O4 NWs. Further applying i-Ag/Co3 O4 NWs as the cathode material, a novel Zn-nitrate battery exhibits a power density of 2.56 mW cm-2 and an FE of 91.4% for NH3 production.
RESUMO
In alkaline solutions, the electrocatalytic conversion of nitrates to ammonia (NH3) (NO3RR) is hindered by the sluggish hydrogenation step due to the lack of protons on the electrode surface, making it a grand challenge to synthesize NH3 at a high rate and selectivity. Herein, single-stranded deoxyribonucleic acid (ssDNA)-templated copper nanoclusters (CuNCs) were synthesized for the electrocatalytic production of NH3. Because ssDNA was involved in the optimization of the interfacial water distribution and H-bond network connectivity, the water-electrolysis-induced proton generation was enhanced on the electrode surface, which facilitated the NO3RR kinetics. The activation energy (Ea) and in situ spectroscopy studies adequately demonstrated that the NO3RR was exothermic until NH3 desorption, indicating that, in alkaline media, the NO3RR catalyzed by ssDNA-templated CuNCs followed the same reaction path as the NO3RR in acidic media. Electrocatalytic tests further verified the efficiency of ssDNA-templated CuNCs, which achieved a high NH3 yield rate of 2.62 mg h-1 cm-2 and a Faraday efficiency of 96.8% at -0.6 V vs reversible hydrogen electrode. The results of this study lay the foundation for engineering catalyst surface ligands for the electrocatalytic NO3RR.
