Indium Phosphide Quantum Dots Integrated with Cadmium Sulfide Nanorods for Photocatalytic Carbon Dioxide Reduction

Photocatalytic conversion of CO₂ into storable fuels is an attractive way to simultaneously address worldwide energy demands and environmental problems. Semiconductor quantum dots (QDs) have gained prominence as candidates for photocatalytic applications due to their many advantages, which include tunability for advanced electronic, optical, and surface properties. Indium phosphide (InP) quantum dots are semiconducting QDs with enormous potential for solar-driven CO₂ reduction. Their advantages include a tunable bandgap, diverse surface chemistry, and nontoxicity. InP QDs and CdS nanorods were integrated using a simple and inexpensive method. CO₂ photoreduction by the CdS-InP composites was evaluated in aqueous solution using triethanolamine as a sacrificial donor. The crystal structures, surface compositions, and morphologies were investigated via X-ray diffraction analysis, X-ray photoelectron spectroscopy, and transmission electron microscopy, respectively. The UV-visible diffuse reflectance spectra of the CdS-InP composites indicated efficient visible light utilization in the 500–550 nm range. The results of photoelectrochemical and photoluminescence analyses illustrated effective charge separation in the composites. The photocatalytic activity of the as-synthesized composites was superior to that of pure CdS. The CO evolution rate of the optimized composite was 216 μmol h⁻¹ g⁻¹ during the first three hours of irradiation and increased steadily over the next 62 hours. We also studied the influences of different solvents, the hole scavenger concentration, and catalyst loading on the performance of the optimized composite.