Photoelectrochemical Nitrate Reduction to Ammonia on Ordered Silicon Nanowire Array Photocathodes

As a new path to green ammonia production, photoelectrochemical nitrate reduction reaction (PEC NO3RR) is investigated for the first time. An Au-decorated ordered silicon nanowire (O_SiNW) array photocathode demonstrates 95.6 % of Faradaic efficiency (FE) to ammonia at 0.2 V-RHE, which represents a more positive potential than the thermodynamic reduction potential of nitrate by utilizing photovoltage. The high FE is possible because both Si and Au surfaces are inactive for competing water reduction to hydrogen. The O_SiNW array structure is favorable to promote the PEC NO3RR relative to planar Si or randomly-grown Si nanowire, by enabling the uniform distribution of small Au nanoparticles as an electrocatalyst and facilitating the mass transport during the reaction. The results demonstrate the feasibility of PEC nitrate conversion to ammonia and would motivate further studies and developments.

Automated summary

The study investigates the photoelectrochemical nitrate reduction reaction (PEC NO3RR) for green ammonia production, achieving a high Faradaic efficiency of 95.6% using an Au-decorated ordered silicon nanowire (O_SiNW) array photocathode. The O_SiNW structure is favorable for promoting the reaction and utilizing photovoltage to achieve high ammonia production efficiency.