Size-dependent photocatalytic activity of Au nanoparticles supported on Ti₃C₂ MXene

In this study, we describe the synthesis of gold nanoparticles (AuNPs) and their direct immobilization onto Ti 3 C 2 MXene. This synthetic approach enables precise control over the AuNP size, affording three hybrid materials composed of Ti 3 C 2 MXene decorated with spherical AuNPs of 39, 14, and 9 nm in diameter. The resulting materials were evaluated as photocatalyst in two well-stablished benchmark reactions: the reduction of nitrophenol and the degradation of organic dyes (Rhodamine B, methyl orange and Congo red). The influence of AuNPs size on photocatalytic performance was systematically investigated, revealing that Au x NPs@MXene with the smallest nanoparticles exhibits the highest activity under mild conditions. The hybrid material Au 0.1 NPs@MXene containing the smallest AuNPs (9 nm) provides quantitative yield in just 10 min whereas the other catalyst require 1 or 2 h. Recycling experiments were carried out to assess catalyst stability and deactivation pathways. A gradual loss of activity was only observed for nitrophenol reduction after five cycles, whereas no significant deactivation was detected for dye degradation. These findings underscore the potential of Au x NPs@MXene-based materials as photocatalyst in sustainable transformations.