Efficient photoelectrocatalytic ammonia synthesis over graphene oxide-modified Fe-based metal-organic frameworks with...

Photoelectrochemical (PEC) N₂ reduction reaction (NRR) using renewable solar energy enables the production of ammonia (NH₃) from H₂O as a hydrogen source under ambient conditions. However, the weak N₂ adsorption and activation and the low light utilization efficiency lead to low NH₃ yield. Herein, we investigate the effect of different Fe-O units on the photoelectrocatalytic ammonia synthesis using Fe-based metal-organic frameworks (MOFs), and modulate the conductivity of MOFs through the electronic interaction between graphene oxide (GO) and ligands to reduce the recombination of photogenerated carriers, thereby enhancing the PEC nitrogen reduction activity. Theoretical calculations suggest that the electron transfer from GO to MIL-88B via hydrogen bonding and the pathway from carbonyl oxygen in the ligand to metal‑oxygen clusters, improves the conductivity of the catalyst. Specially, the optimized MIL-88B/GO-8 photocathode exhibits an excellent NRR performance with maximum ammonia yield rate of 21.4 mg h^-1 m^-2 at -0.4 V and a Faraday efficiency of 9.7 % at -0.3 V. This work indicates that the efficient optoelectronics utilization through the synergism between MOFs and carbon-based conductive components in composite catalysts provides a potential for an efficient NRR under ambient conditions.