Construction of a sea-urchin liked S-Scheme heterojunction: A case study using 3D CoNiO2/W18O49 composite for efficient CO2 photoreduction

The CO₂ photoreduction (CO₂ PR) technique is widely acknowledged as a promising approach to mitigating energy shortage crises. Among various strategies, enhancing the efficiency of charge carrier separation and broadening the spectral response range are effective means to advance the development of CO₂ PR. In this study, a novel S-scheme heterojunction CoNiO₂/W₁₈O₄₉ composite catalyst was synthesized through a two-step hydrothermal method. By leveraging its heterostructure and enhanced visible-light absorption capacity, the composite demonstrates improved carrier separation efficiency and superior CO₂ molecule capture capability, thereby achieving exceptional CO₂ PR performance. The optimized CW-3 sample exhibited remarkable CO and CH₄ evolution rates of 87.17 and 92.42 μmol g⁻¹ h⁻¹, respectively, representing 6-fold and 33-fold enhancements compared to pristine CoNiO₂. Combined theoretical calculations and systematic characterizations conclusively demonstrated the formation mechanism of the intrinsic electric field at the S-scheme heterojunction interface. The composite material simultaneously enhanced visible-light absorption through optimized band alignment and significantly improved charge carrier separation efficiency driven by synergistic interfacial charge transfer and band bending effects. This integrated enhancement mechanism stemmed from the complementary electronic interactions between CoNiO₂ and W₁₈O₄₉ components within the heterostructure architecture.