Gold and nanosized titanium carbide MXene heterozygotes as highly efficient visible-light responsive photocatalysts for ammonia synthesis

Utilizing sunlight to drive photocatalytic conversion of N2 into NH3 is a promising approach to mitigate the substantial energy consumption associated with the Haber–Bosch process. However, significant challenges remain unaddressed before the practical application of photocatalysts can be realized. Various materials and nanoscale design strategies have been investigated with the aim of achieving a high quantum yield. Among these, MXenes can be a promising photocatalyst for NH3 synthesis due to its excellent N2 fixation performance. In this work, we investigate the use of nanosized Ti3C2 MXene and plasmonic gold nanoparticles (AuNPs) for NH3 synthesis with visible light. We observed a formation of heterozygote structures between AuNPs and reduced nanosized Ti3C2, resulting in a 4.4-fold increase in the photocatalytic activity compared to that of reported microscale Ti3C2 with AuNPs nanocomposites. The improved photocatalytic performance is originated from the enhanced light absorption of AuNPs, and the efficient N2 fixation by the nanosized Ti3C2 MXene with a reduced chemical state, which is demonstrated experimentally with gas chromatographic analysis. The various experimental conditions involving catalysts, concentration, pH, and scavengers are investigated, the highest photocatalytic performance was achieved with the heterozygote structures of AuNPs and nanosized Ti3C2 MXene under optimized conditions, and yielding 5334 μmol gcat−1 h−1 of ammonia, an amount at least 13-fold higher than that of previously developed photocatalysts.