Sub-10 nm metal-dispersed crystalline C3N5 for photocatalytic CO2 reduction to produce formic acid and acetic acid

Abstract

The N-rich carbon nitride allotrope, C₃N₅, is a promising candidate for solar-driven CO₂ conversion (CO2RR) due to its electronic and light absorption properties. Its crystalline form is an ideal base for further modification through metal loading. This work compares different metals (Ag, Bi, Mg, W) dispersed on crystalline C₃N₅ (CCN) through a facile photodeposition method, confirmed by transmission electron microscopy to result in nanoparticulate Ag with a 10.62 nm average diameter. 1.5 wt% was the optimal amount of Ag-dispersed on CCN (Ag1.5) with the highest performance for CO 2 RR, with an apparent quantum efficiency of 5.3 for CO.The production of CO, formic acid and acetic acid on Ag1.5 was improved by 4, 17 and 3.8times compared to CCN, respectively. This stems from the catalytic ability, increased light absorption of Ag1.5, and rapid charge transfer across CCN to Ag from time-resolved photoluminescence. Crucial reaction intermediates (e.g. *COOH, Ag + ^-CO*, HCO₃ ) were identified through in-situ diffuse reflectance infrared Fourier transform spectroscopy, confirming C-C bonding and CO₂ activation on Ag1.5. As such, this work represents great strides for the synergy of metal loading and structural engineering in carbon nitride toward artificial photosynthesis.