ACS Catal.: Mo5+/Mo6+可逆转化协同质子耦合电子转移用于CO2光还原，CH4选择性接近100%

第一作者：常州大学 Qian Liang

通讯作者：浙江海洋大学 周英棠，上海科技大学 彭蒸，常州大学 李忠玉，苏州大学  康振辉

DOI：https://doi.org/10.1021/acscatal.4c04994

调节质子耦合电子转移（PCET）过程以避免还原活性位点上质子和电子区域的不平衡是光催化CO₂还原反应中决定产物选择性的关键。作者发现可逆的Mo⁵⁺/Mo⁶⁺作为介质可以调节Bi₂MoO₆纳米片/In₂O₃微管（BI）催化剂的质子和电子转移过程。形成的质子耦合电子转移使太阳能-甲烷效率达到0.15%，CH₄选择性接近100%，在纯水中CH₄产率为46.37 μmol g^-1 h^-1。实验和理论计算清楚地验证了作为H₂O氧化中心的In位点提供质子，利用Mo位点对质子和电子进行调控形成近似的电中性质子/电子对，这些质子/电子对联合转移到作为CO₂吸附/还原中心的Bi位点上，从而在Bi位点上实现精确的氢化，结合* CH₃O关键中间体形成CH₄。

Figure 1. Schematic illustration and characterization of the BI catalyst. (a) Synthetic route of the BI catalyst and schematic illustration of enhanced CO2RR activity with good mass transfer. (b) XRD patterns of Bi2MoO6, In2O3, and BI catalysts. (c) EPR and (d) UV−vis diffuse reflection spectra of In2O3, Bi2MoO6, and BI40. (e) SEM image of BI40 and TEM image of a pure In2O3 tube (inset). (f) STEM-EDX mapping analysis of BI40. (g) HRTEM image of BI40.

Figure 2. Photocatalytic performance of CO2RR. (a) Gas evolution performance of 5 h over optimal BI40 under simulated sunlight irradiation. (b) Yields of CO and CH4, and CH4 selectivity over In2O3, Bi2MoO6, and BI catalysts. (c) AQE values under different wavelengths. (d) Performance comparison of BI40 with reported photocatalysts (Table S5). (e) Stability testing of optimal BI40 for CO2RR. (f) Mass spectra of products for photocatalytic 13CO2 conversion over BI40.

Figure 3. In situ NAP-XPS spectra. XPS spectra of (a) Bi 4f, (b) Mo 3d, and (c) In 3d under the following conditions (from bottom to top): ex situ XPS spectra of Bi2MoO6 and In2O3; in situ NAP-XPS spectra of BI40 under UHV; after introduction of CO2 and H2O (the ratio of PCO2 to PH2O is 19:1, Ptotal = 0.5 mbar), corresponding to exposure to simulated solar illumination. (d) Change transfer mechanism of BI. (e) Schematic illustration of the effect of Bi and Mo sites on CO2RR. In situ NAP-XPS spectra of (f) O 1s and (g) C 1s for BI40 under UHV, after introduction of CO2 and H2O (the ratio of PCO2 to PH2O is 19:1), corresponding to exposure to simulated solar illumination. (h) Photograph of BI40 in UHV under the dark/light irradiation condition.

Figure 4. Interpretation of photocatalytic mechanisms. (a) In situ Raman spectra of BI40 with CO2-saturated H2O under different irradiation times. (b) CO2-TPD of Bi2MoO6, In2O3, and BI40. (c, d) Charge density difference on the interface between the catalyst and adsorbed CO2. (e) Electron localization function on Bi2MoO6 and BI40. (f) Partial density of states (PDOS) of the d-orbital in Bi2MoO6 and BI40. (g) Schematic illustration of CPET using reversible Mo5+/Mo6+.

Figure 5. Characterization of the formed species during CO2RR. (a) In situ FTIR spectra of BI40 for the CO2RR. (b) Free energy diagram of the reduction of CO2 to CH4 over Bi2MoO6 and BI40. (c) Schematic illustration of CO2 reduction to CH4 over the BI catalyst.

Concerted Proton-Coupled Electron Transfer by Mo5+/Mo6+ Reversible Transformation for CO2 Photoreduction with Nearly 100% CH4 Selectivity

https://doi.org/10.1021/acscatal.4c04994