Surface Engineering of Indium Oxide by Nickel Oxide Clusters for Driving Methanol Production from CO ₂ Hydrogenation

High Resolution Image Download MS PowerPoint Slide The hydrogenation of CO 2 into methanol offers a promising approach to carbon sequestration and a potential approach to storing hydrogen derived from renewable energy. Herein, we report a facile surface engineering strategy by anchoring nickel oxide (NiO) clusters onto the surface of the commercial indium oxide (In 2 O 3 ) to drive methanol synthesis. The anchored NiO clusters brought about the transfer of electrons from the NiO cluster to the In 2 O 3 surface, which was revealed through a series of characterizations. This electronic interaction led to an increased level of oxidation of the anchored NiO clusters and facilitated the reduction of the In 2 O 3 surface, thereby generating more active sites such as oxygen vacancies (OVs). More importantly, the anchored NiO clusters contributed to the dissociation activation of H 2 compared to the OV site of pure In 2 O 3 . As a result, the CO 2 conversion and methanol space-time yield were increased by approximately 2-fold and 1.4-fold, respectively. The high-pressure operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) measurements suggested that the methanol production was promoted by the formation of formate (HCOO*) and its subsequent conversion to methoxy species (CH 3 O*). The in situ X-ray adsorption experiments under working conditions indicated that the anchored NiO clusters remained in the oxidized state, with a slight partial reduction. This likely guaranteed the activation of H 2, which not only contributed to the formation of more surface-active OVs during the reaction but also offered more active H species in the stepwise hydrogenation reactions for methanol synthesis.