Engineering Stable Surface Oxygen Vacancies on ZrO₂ by Hydrogen-Etching Technology: An Efficient Support of Gold...

The surface structure of supports is crucial to fabricate efficient supported catalysts for water-gas shift (WGS). Here, hardly reducible ZrO₂ was etched with hydrogen (H), aiming to modify surface structures with sufficient stable oxygen vacancies. After deposition of gold species, the obtained khaki ZrO₂-H notably improved WGS catalytic activities and stabilities in comparison to the traditional white ZrO₂. The characterization results and quantitative analysis indicate that sufficient surface oxygen vacancies of ZrO₂-H support give rise to more metallic Au⁰ species and higher microstrain, which all boost WGS catalytic activities. Furthermore, optoelectronic properties were successfully used to correlate with their WGS thermocatalytic activities, and then a modified electron flow process was proposed to understand the WGS pathway. For one thing, the introduction of surface oxygen vacancies narrowed the band gap of ZrO₂ and decreased the Ohmic barrier, which facilitated the flow of "hot-electron". For another thing, the conduction band electrons can be easily trapped by oxygen vacancies of ZrO₂ supports, and then these trapped electrons immediately take part in reduction of H₂O to H₂. Thus, the electron recombination was suppressed and the WGS catalytic activity was improved. It is worth extending H₂-etching technology to improve other thermocatalytic reactions.