An old catalyst and light speed up CO2 reduction
The RWGS reaction (CO₂ + H₂ ↔ CO + H₂O) enables the conversion of CO₂ into carbon monoxide, a key feedstock for syngas and the subsequent production of fuels and chemicals. The main challenge is the high energy demand, as high temperatures are typically required to achieve the desired reaction rates. In this study, we demonstrated that visible light can enhance the activity even of a well-established industrial Cu/ZnO/Al₂O₃ (CZA) catalyst.
Upon illuminating CZA with visible light, we achieved an almost sixfold higher CO formation rate compared with the reaction in the dark, with the light effect being strongest at temperatures below 230 °C. Blue photons (400–500 nm) proved most effective, where the catalyst reached a high apparent quantum yield of up to 47%. Illumination was also accompanied by a pronounced decrease in the activation energy for CO formation (83 → 44 kJ mol⁻¹), indicating a light-induced change in the reaction mechanism rather than a purely thermal effect.
Using in situ/operando approaches (including transient DRIFTS and kinetic analysis), we investigated the mechanistic origin and found that under illumination CO is formed predominantly via the carboxylate pathway (COOH*). The key effect of light is accelerated H₂ dissociation and an approximately fivefold higher surface coverage of active H*, which promotes the conversion of carboxylate intermediates to the final products. Overall, the results confirm that appropriate illumination can improve the performance of catalytic processes—even on established industrial catalysts—without the need to develop new materials.
More info: https://www.sciencedirect.com/science/article/pii/S1385894725125291?via%3Dihub
Contact: petar.djinovic(at)ki.si