Solar-Powered Gram-Scale Ammonia Production from Nitrate

The photoelectrochemical (PEC) method has the potential to be an attractive route for converting and storing solar energy as chemical bonds. In this study, a maximum NH₃ production yield of 1.01 g L^-1 with a solar-to-ammonia conversion efficiency of 8.17% through the photovoltaic electrocatalytic (PV-EC) nitrate (NO₃ ^-) reduction reaction (NO₃ ^-RR) is achieved, using silicon heterojunction solar cell technology. Additionally, the effect of tuning the operation potential of the PV-EC system and its influence on product selectivity are systematically investigated. By using this unique external resistance tuning approach in the PV-EC system, ammonia production through nitrate reduction performance from 96 to 360 mg L^-1 is enhanced, a four-fold increase. Furthermore, the NH₃ is extracted as NH₄Cl powder using acid stripping, which is essential for storing chemical energy. This work demonstrates the possibility of tuning product selectivity in PV-EC systems, with prospects toward pilot scale on value-added product synthesis.