Self-Assembled Zn_1–xO/TiO₂ Nanocomposite as a Novel p–n Heterojunction for Selective CO₂-to-CO Photoreduction

Abstract

Selective CO2 photoreduction to valuable chemicals is promising for a carbon-neutral future and still remains a challenge. Herein, Zn vacancy-rich ZnO (Zn1–x O) nanoparticles were used as cocatalyst to construct a Zn1–x O/TiO2 nanostructure via the self-assembly process. The existence of Zn vacancies triggered the intimate contact between Zn1–x O and TiO2 through the Ti–O–Zn bonds. Theoretical and experimental results show that the hybridization of Zn1–x O and TiO2 resulted in the formation of a p–n heterojunction, leading to the enhanced separation efficiency of photoinduced electron–hole pairs. As a result, the optimized Zn1–x O/TiO2 nanocomposite exhibited nearly 100% selectivity of CO2-to-CO photoreduction, and the productivity was 4.2 times higher than that of pristine TiO2. In situ Fourier transform infrared spectra along with theoretical calculations were also conducted to investigate the mechanism of the selective photocatalytic CO2-to-CO process. It is concluded that the charge depletion on the TiO2 surface induced by the charge transfer from Zn1–x O to TiO2 can lower the energy barrier of CO* desorption and convert the endothermic CO* desorption process into an exothermic reaction step, thus triggering selective CO production. This work provides a new perspective on the rational fabrication of nanostructures for efficient and selective photocatalytic CO2 conversion through intermediate modulation.

Hierarchical (CdZnCuCoFe)S1.25/ZnIn2S4 Heterojunction for Photocatalytic CO2 Reduction: Insights into S-Scheme Charge Transfer Pathways in Type-I Band Alignment

“…The in situ FTIR spectrometry in the presence of Ar and H 2 O vapor was performed to study the oxidation process. As shown in Figure S5, the absorption peak at 834 cm –1 gradually increased with longer irradiation time, corresponding to the O–O stretching of H 2 O 2 . Thus, it can be concluded that the absence of O 2 was due to the generation of peroxide intermediate.…”

“…As shown in Figure S5, the absorption peak at 834 cm −1 gradually increased with longer irradiation time, corresponding to the O−O stretching of H 2 O 2 . 43 Thus, it can be concluded that the absence of O 2 was due to the generation of peroxide intermediate. Furthermore, a 27 h continuous stability test was performed to assess the practical CO 2 photoreduction applications of the HES/ZIS-10 sample.…”

Photocatalytic Conversion of CO2 to CO with a p–n Heterojunction Based on Core–Shell β-Ga2O3@CoGa2O4 Nanorods

“…Over the past few decades, extensive research has been conducted on various semiconductor materials with the potential to reduce CO 2 in direct sunlight. , However, practical applications of these semiconductors face challenges like limited light absorption and rapid charge recombination . To enhance the efficiency of semiconductor photocatalysts, many approaches have been developed to tackle these issues, such as doping, defect engineering, loading cocatalysts, and heterogeneous structure design . However, the photocatalytic efficiency of photocatalysts is still limited by the ability of separation or combination of photogenerated electron–hole pairs.…”

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

“…To further improve the photocatalytic ability of TiO 2 , researchers recently studied a series of new catalysts for photocatalytic H 2 and CO 2 reduction reactions, such as 3D/2D TiO 2 @Ti 3 C 2 MXene/Bi 2 S 3 , TiO 2 /C 3 N 4 , 3D ZnIn 2 S 4 /TiO 2 and so on. Of course, some scholars use the advantages of precious metals in catalysis to improve the performance of catalysts by incorporating Pt, Au, and Ag. , In addition, the performance of the TiO 2 catalyst was also improved by designing the morphology of composite materials, , Z-scheme heterojunctions, , and p–n heterojunctions . However, there are few research studies on S-scheme heterojunction catalysts constructed with cheap inorganic materials and even fewer research studies on catalysts that can photocatalyze both H 2 production and CO 2 reduction …”