Tungsten bronze Cs_0.33WO₃ nanorods modified by molybdenum for improved photocatalytic CO₂ reduction directly from air

Abstract

Photocatalytic CO₂ reduction is thought to be a promising strategy in mitigating the energy crisis and several other environmental problems. Hence, modifying or developing suitable semiconductors with high efficiency of photocatalytic CO₂ reduction property has become a topic of interest to scientists. In this study, a series of Mo-modified Cs_0.33WO₃ tungsten bronze were prepared using a “water-controllable releasing” solvothermal method to produce effective photocatalytic CO₂ reduction performance. Interestingly, Mo atoms replaced W partially within the hexagonal crystal structure, leading to a significant increase in photocatalytic CO₂ reduction activity of Cs_0.33WO₃. The 5% Modoped compound displayed the best performance, with the production yield rates of 7.5 µmol g⁻¹ h⁻¹ for CO and 3.0 µmol g⁻¹ h⁻¹ for CH₃OH under low concentration of CO₂ under anaerobic conditions, which is greatly higher than those of pure Cs_0.33WO₃ (3.2 µmol g⁻¹ h⁻¹ for CO and 1.2 µmol g⁻¹h⁻¹ for CH₃OH) and Mo-doped W₁₈O₄₉ (1.5 µmol g⁻¹ h⁻¹ for CO and 0 µmol g⁻¹ h⁻¹ for CH₃OH). More importantly, the as-prepared Mo-doped Cs_0.33WO₃ series could also induce the photocatalytic reduction of CO₂ directly from the air in the presence of oxygen, which is beneficial for practical applications. The superior photocatalytic performance of Mo-doped Cs_0.33WO₃ series over the popular reduced WO₃ may be due to the increase in light absorption induced by the localized surface plasmon resonance (LSPR) effect of Mo⁵⁺, large improved charge separation ability, and the co-effect of Mo and Cs in crystal. This study provides a simple strategy for designing highly efficient photocatalysts in low concentration of CO₂ reduction.

摘要

光催化还原CO₂被公认为一种很有潜力缓解能源危机和环 境污染的方法. 理所当然地, 改性或者开发合适的光催化材料使其 拥有高的光催化CO₂还原活性成为了一个研究热点. 在本工作中, 我们用一种“控制水释放”的水热法制备了一系列钼改性的钨青铜 Cs_0.33WO₃, 以期该物质能拥有良好的光催化CO₂还原性能. 有趣的 是, 通过部分Mo取代晶体中的W, Cs_0.33WO₃的光催化CO₂还原性能 得到显著提高, 明显优于纯的Cs_0.33WO₃和Mo掺杂的W₁₈O₄₉. 5%Mo 掺杂的Cs_0.33WO₃在厌氧气氛中展现出了最优的光催化还原低浓度 CO2性能, 其中CO产率为7.5 μmol g⁻¹ h⁻¹, 而甲醇产率为 3.0 μmol g⁻¹ h⁻¹. 更重要的是, Mo掺杂的Cs_0.33WO₃系列在氧气存 在的条件下, 能够直接光催化还原空气气氛中的CO₂, 这有利于其 实际应用. Mo掺杂的Cs_0.33WO₃光催化活性优于其他对应材料, 主 要原因是Mo⁵⁺的等离子共振引起的光吸收增强、大大提高的电荷 分离能力以及Mo和Cs在晶体中的共同作用等. 本工作可能为设计 用于高效低浓度CO₂还原的光催化材料提供一种简易的方法.