Pd-loaded unique urchin-structured Ga2O3 for selective CO2 photoreduction to CH4

Abstract

The effectiveness of photogenerated carrier separation and the restricted number of active sites result in unsatisfactory CO₂ photoreduction efficacy. Furthermore, the CO₂ photoreduction process always shows the drawback of low product selectivity. Herein, a unique urchin-structured Ga₂O₃-based photocatalyst with Pd loading was designed and the relationship between the loading amount and the optimal catalytic performance was investigated. Results show that Ga₂O₃ synthesized at 90 °C with 2% Pd loading amount (2%Pd/Ga₂O₃-90) gives an excellent yield of up to 107.48 μmol g⁻¹ h⁻¹ and 99.5% selectivity of CH₄. The larger specific surface area (44.7 m² g⁻¹) of Ga₂O₃ prepared at 90 °C (Ga₂O₃-90) can provide more active sites, simultaneously, the highly dispersed Pd nanoparticles act as both active sites for CO₂ adsorption and activation and as centers for electron capture to facilitate the photogenerated carrier separation effectively. Furthermore, the in situ DRIFTS spectra and CO adsorption isotherm of 2%Pd/Ga₂O₃-90 confirm the presence of key intermediates such as *CO, and *CHO, indicating that CO can be captured by Pd and further protonated, thereby exhibiting 99.5% selectivity of CH₄. This work provides valuable insights into the preparation of catalysts with a high specific surface area and highly selective CO₂ photoreduction to CH₄.