Urchin-like TiO₂/CdS Nanoparticles Forming an S-scheme Heterojunction for Photocatalytic Hydrogen Production and CO₂ Reduction

The use of semiconductor nanoparticle heterojunctions for photocatalytic activities is a very attractive strategy. TiO₂/CdS is widely used in the photocatalytic degradation of pollutants, but there are few reports on photocatalytic hydrogen production and CO₂ reduction. In this work, rod and fishbone CdS nanoparticles were prepared by the hydrothermal method, and S-scheme TiO₂/CdS nanoparticles with sea urchin morphology were designed. With Na₂S and Na₂SO₃ as sacrifice agents, the H₂ yield of TiO₂/CdS was 1.07 mmol·h^-1·g^-1, and with [Ru(bpy)₃]Cl₂·6H₂O as the photosensitizer and TEOA as the sacrifice agent, the rate of CO production from CO₂ reduction was 47.67 μmol·h^-1·g^-1. The preparation rates of H₂ and CO were 9 times and 13.3 times for TiO₂ nanoparticles and 3.1 times and 1.7 times for fishbone CdS/TiO₂ composite particles, respectively. The electron transfer path and photocatalytic mechanism were deduced by EPR, TRPL, UPS, etc. The results showed that the construction of the S-scheme heterojunction enhanced the photocatalytic performance of the catalyst. We synthesized the S-scheme TiO₂/CdS nanoparticle heterojunction for the first time and applied it to the photocatalytic production of H₂ and reduction of CO₂. This work provides an effective reference for designing high-performance inorganic S-scheme heterojunction catalysts.