Present State and Future Outlook of Ammonia Production through Photocatalytic Nitrate Reduction

Abstract

Ammonia (NH3) production has gained increasing attention owing to its versatility in both industrial and agricultural applications, as well as its potential as a next-generation energy carrier with a high hydrogen density. Given the energy-intensive and environmentally impactful nature of the Haber–Bosch process, there is a pressing need for a sustainable NH3 synthesis method under ambient conditions. Nitrate (NO3−) emerges as a compelling nitrogen source due to its numerous advantages over inert nitrogen (N2) gas, such as its relatively low dissociation energy and high aqueous solubility. Moreover, NO3− is a common contaminant found in wastewater, posing a threat to aquatic ecosystems. The photocatalytic NO3− reduction to NH3, which utilizes sunlight to convert contaminants into value-added chemicals, aligns perfectly with the need for sustainable solutions. This perspective reviews the latest advancements in the field of photocatalytic NO3− to NH3 conversion. The mechanism behind the conversion of NO3− to NH3 is briefly explained, and photocatalysts exhibiting high selectivity and activity in NH3 production, along with other influential factors, are summarized. Additionally, current challenges and future prospects within this field are discussed.This perspective will provide a valuable guidance for future research in the realm of photocatalytic NH3 production via NO3− reduction.