Recent advances in the development of photocatalytic technology for nitrate reduction to ammonia

The pursuit of achieving net zero emissions by 2050, a target established following the adoption of the SDGs in 2015, has had a significant impact on the industrial sector. The conventional method for producing ammonia (NH3) known as the Haber-Bosch process, currently employed for commercial purposes, has adverse environmental effects and is not economically feasible due to its high operating temperatures and pressures (approximately 500 °C and 200 MPa). This results in the generation of substantial CO2 emissions, inefficient energy usage, and unsustainable reliance on fossil-based raw materials. To address this, researchers are focusing on alternative methods for converting nitrates to ammonia, given that nitrates are pollutants stemming from agriculture, power generation, and related industrial activities. One promising approach under development is photocatalysis which employs solar energy and catalyst to convert nitrates into ammonia using more environmentally friendly and cost-effective means. This review paper provides an extensive and detailed exploration of the reduction of nitrate to ammonia through photocatalytic technology. The discussion encompasses various aspects including thermodynamics and kinetics, photocatalysts development, factors affecting the ammonia production efficiency, the detailed mechanism behind ammonia production based on experimental and DFT calculations approach, challenges, and prospective areas of advancement based on earlier research. In essence, this comprehensive review steers researchers toward the necessary future endeavors that are essential for the broad adoption of the photocatalytic method in addressing nitrates as toxic pollutants.