Developing catalysts capable of efficiently utilizing both visible and near-infrared wavelengths of the solar spectrum for CO2 hydrogenation has led to growing interest in reduced TiO2 materials. Achieving efficient long-wavelength solar light harvesting requires a high concentration of oxygen vacancies (OV). However, extensive OV formation can lead to atomic rearrangements within TiOX, causing a dispersion of OV throughout the material, as opposed to creating localized and distinct OV sites typical of crystalline TiOX, which interact directly with reactants. In this study, we synthesized amorphous black TiOX (AM-TiOX) catalysts and thoroughly characterized their surface properties, including acidity and the desorption bond strengths of H2 and CO2. Density functional theory (DFT) simulations were performed to analyze the hydrogen adsorption profile and structural changes in the material due to OV formation. We found that hydrogen mobility on the surface is restricted due to strong hydrogen bonding. The CO2 hydrogenation process was investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), enabling the development of a reaction pathway to elucidate the catalyst’s selectivity towards CO and the effect of light irradiation on product formation rates. Notably, m-HCO3* formation was favored, with CO and CH4 production proceeding primarily via the formate pathway. To enhance catalyst stability against oxidation during reaction, the surface was decorated with Ru particles. The findings of this study are relevant to catalysts that leverage extensive Oᵥ formation as a strategy to extend light responsiveness, as well as to the design of catalysts for CO2 hydrogenation to CO.
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Nano Research 2025, 18(3): 94907218
Published: 03 March 2025
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