Cu/Au nanoparticles embedded in g-C3N4 nanosheets toward efficient photocatalytic CO2/NO conversion and H2 generation

Efficient separation of photogenerated charge carriers is essential for enhancing photocatalytic redox reactions, including CO 2 reduction, NO removal, and H 2 generation. In this study, a highly active g-C 3 N 4 -based photocatalyst was developed by loading finely dispersed Cu nanoparticles onto Au modified g-C 3 N 4 nanosheets. A mechano-chemical pre-treatment step proved critical for achieving a homogeneous distribution of metal species within the g-C 3 N 4 framework. While Au-incorporated g-C 3 N 4 alone exhibited poor photocatalytic performance which is attributed to the strong blue-green luminescence indicative of rapid charge recombination, the subsequent introduction of Cu dramatically enhanced the catalytic activity of the material. The preferential growth of Cu species at Au sites plays a key role, as the synergistic Cu-Au co-incorporation significantly improved charge carrier transport efficiency and broadened the light absorption range. As a result, the Cu/Au-g-C 3 N 4 nanosheets composites demonstrate outstanding photocatalytic performance. A high H 2 evolution rate of 4802 µmol g -1 h -1 was achieved under light irradiation. In photocatalytic CO 2 reduction, CO and CH 4 were produced at rates of 6.64 and 3.42 µmol g -1 h -1 , respectively. Notably, the catalyst exhibits excellent NO removal capability, achieving a 64% NO conversion rate with an impressively low NO 2 selectivity of only 4.2%, a parameter of particular importance for minimizing secondary environmental hazards. These enhancements are attributed to the rapid charge separation pathways established by the Au-Cu dual-metal system, increased adsorption affinity of Cu sites toward NO and CO 2 molecules. Collectively, these findings highlight g-C 3 N 4 -based heterojunctions as highly promising multifunctional photocatalysts with broad potential across energy and environmental applications. • A highly efficient Cu and Au incorporated g-C 3 N 4 based photocatalyst was fabricated. • The photocatalyst showed a high H 2 generation rate of 4802 μmol g -1 h -1 . • In case of photocatalytic CO 2 reduction, the CO and CH 4 evolution rate of the optimized composites were 6.64 and 3.42 μmol g -1 h -1 , respectively. • The photocatalyst exhibited excellent NO removal rate of 64% with low NO 2 selectivity of 4.2%.