Photocatalysis for Sustainable Nitrogen Fixation: Fundamentals, Catalyst Design, Nanoarchitectonics, Applications, and Future Prospects

Photocatalytic nitrogen fixation has evolved as potential sustainable technique for producing ammonia in contrast to Haber-Bosch (HB) process. In this process, semiconductor-based materials are utilized in the presence of light and water, thereby making it less energy-intensive and more eco-friendly. However, photocatalytic materials utilized in nitrogen fixation have several disadvantages, including limited chemisorption and activation of nitrogen, low light absorption, rapid charge recombination, and sluggish kinetics. To overcome these issues, design of the catalyst and tailoring of active surface sites are vital so that enhanced performance can be achieved. Also, there is debate about the correct determination of ammonia due to interference by nitrogenous impurities. Taking all these factors into consideration, this review examines the recent reports on enhanced photocatalytic performance of defects modified (vacancy and doping), facet-engineered, and heterojunction-based catalysts for nitrogen fixation. The different ammonia quantification techniques like Nessler's reagent, indophenol method, ion chromatography (IC), etc. have been discussed in detail along with issues associated with them. Finally, the existing challenges and outlook of this emerging technology are presented. It is expected that this review will assist the researchers in understanding the current state of this field and effectively implementing it to pave the way for future advancements.