Synergy Between Hydroxyl and Oxygen Vacancy Enhances CO Adsorption on Oxide Surface

Oxide catalysts often outperform their metal counterparts in selectivity for CO hydrogenation reactions. However, their wide applications are hindered by inherently lower CO conversion rates, primarily attributed to the weak adsorption of CO on oxide surfaces. In this work, we report that the combination of hydroxyl (OH) groups and oxygen vacancies (V_O) on a single-layer MnO_x surface creates a synergistic effect that facilitates strong CO adsorption. As such, CO can stably adsorb on the MnO_x surface under ultra-high vacuum at room temperature, with a desorption temperature exceeding that on the benchmark Pt(111) surface. In contrast, CO fails to adsorb on MnO_x surfaces containing only OH groups or only V_O. Moreover, the CO coverage on the MnO_x surface can be tuned by adjusting the relative concentrations of OH groups and V_O. Theoretical calculations reveal that the presence of neighbouring OH further increases charge accumulation at Mn sites surrounded with V_O, which provides more electrons for CO-surface bonding and consequently strengthens CO adsorption. This work highlights the cooperative role of surface OH and V_O in enhancing CO adsorption, providing valuable insight into CO activation on metal oxide surfaces and offering guidance for improving syngas conversion reactions.