Green-Emitting Graphene Quantum Dot-Modified Ru/CeO2/SiO2 Nanoislands for Photocatalytic CO2 Reduction

Abstract Photocatalytic CO2 reduction is limited by weak visible-light use and fast carrier recombination in many CeO2-based catalysts. Herein, green-emitting graphene quantum dots (g-GQDs) were coupled with Ru/CeO2/SiO2 nanoislands to build a CeO2-centered photocatalyst. SiO2 disperses the CeO2 nanoislands, Ru promotes electron utilization, and g-GQDs extend the visible-light response while providing an interfacial charge-transfer channel. The apparent optical transition energy decreases from 2.25 eV for CS-2 to 2.06 eV for 3 wt % GQDs/RCS-2, accompanied by lower interfacial resistance and weaker PL emission. As a result, 3 wt % GQDs/RCS-2 gives a CO evolution rate of 12.58 mmol g–1 h–1, 1.69 times that of CS-2, with stable cycling performance. This work provides a simple interface-modulation strategy for improving CeO2-based photocatalytic CO2 reduction.