A hierarchical z-scheme CdS–WO₃ photocatalyst with enhanced CO₂ reduction activity

The development of an artificial photosynthetic system is a promising strategy to convert solar energy into chemical fuels. Here, a direct Z-scheme CdS–WO₃ photocatalyst without an electron mediator is fabricated by imitating natural photosynthesis of green plants. Photocatalytic activities of as-prepared samples are evaluated on the basis of photocatalytic CO₂ reduction to form CH₄ under visible light irradiation. These Z-scheme-heterostructured samples show a higher photocatalytic CO₂ reduction than single-phase photocatalysts. An optimized CdS–WO₃ heterostructure sample exhibits the highest CH₄ production rate of 1.02 μmol h⁻¹ g⁻¹ with 5 mol% CdS content, which exceeds the rates observed in single-phase WO₃ and CdS samples for approximately 100 and ten times under the same reaction condition, respectively. The enhanced photocatalytic activity could be attributed to the formation of a hierarchical direct Z-scheme CdS–WO₃ photocatalyst, resulting in an efficient spatial separation of photo-induced electron–hole pairs. Reduction and oxidation catalytic centers are maintained in two different regions to minimize undesirable back reactions of the photocatalytic products. The introduction of CdS can enhance CO₂ molecule adsorption, thereby accelerating photocatalytic CO₂ reduction to CH₄. This study provides novel insights into the design and fabrication of high-performance artificial Z-scheme photocatalysts to perform photocatalytic CO₂ reduction. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.