Methanol synthesis by CO2 hydrogenation is attractive in view of avoiding the environmental implications associated with the production of the traditional syngas feedstock and mitigating global warming. However, there still is a lack of efficient catalysts for such alternative processes. Herein, we unveil the high activity, 100 % selectivity, and remarkable stability for 1000 h on stream of In2 O3 supported on ZrO2 under industrially relevant conditions. This strongly contrasts to the benchmark Cu-ZnO-Al2 O3 catalyst, which is unselective and experiences rapid deactivation. In-depth characterization of the In2 O3 -based materials points towards a mechanism rooted in the creation and annihilation of oxygen vacancies as active sites, whose amount can be modulated in situ by co-feeding CO and boosted through electronic interactions with the zirconia carrier. These results constitute a promising basis for the design of a prospective technology for sustainable methanol production.

Methanol synthesis by CO 2 hydrogenation is attractive in view of avoiding the environmental implications associated with the production of the traditional syngas feedstocka nd mitigating global warming.H owever,t here still is al acko fe fficient catalysts for such alternative processes. Herein, we unveil the high activity,1 00 %s electivity,a nd remarkable stability for 1000 ho ns tream of In 2 O 3 supported on ZrO 2 under industrially relevant conditions.T his strongly contrasts to the benchmark Cu-ZnO-Al 2 O 3 catalyst, which is unselective and experiences rapid deactivation. In-depth characterization of the In 2 O 3 -based materials points towards am echanism rooted in the creation and annihilation of oxygen vacancies as active sites,w hose amount can be modulated in situ by co-feeding CO and boosted through electronic interactions with the zirconia carrier.T hese results constitute ap romising basis for the design of ap rospective technology for sustainable methanol production.Methanol is akey building block in the chemical industry, [1] with prospects as asustainable energy carrier if its production is accomplished from CO 2 (captured from large-point emitters) and H 2 (retrieved from renewable sources). [2] This application demands novel catalysts as the ternary Cu-ZnO-Al 2 O 3 system currently employed for methanol synthesis from mixed syngas (CO/CO 2 /H 2 )e xhibits limited activity in CO 2 hydrogenation, because of the inhibiting effect of the water byproduct, [3] low selectivity,owing to its significant activity in the parasitic reverse water-gas shift (RWGS) reaction, [4] and insufficient stability,d ue to water-induced sintering of the active phase. [5] Furthermore,t he intricate network of syner-gistic structural and electronic effects between its components hampers the rational optimization of this material. [4a, 6] Among other catalysts studied, [7] only Cu-ZnO-Ga 2 O 3 /SiO 2 and LaCr 0.5 Cu 0.5 O 3 displayed improved methanol formation rates and high selectivities (up to 99.5 %), but their scalability and long-term stability have not been assessed. Recent experiments on Cu/CeO x /TiO 2 model surfaces [8] also showed promising results,but no attempt has been made to translate this material into ap ractically relevant polycrystalline solid.In our quest for as uitable catalyst, we were intrigued by the much simpler In 2 O 3 system. This reducible oxide is commonly used together with SnO 2 as av ery stable conductive transparent layer in organic light-emitting diodes and thin-film transistors. [9] Moreover,i th as demonstrated high activity and selectivity in multiple catalytic transformations involving CO 2 ,i ncluding electrochemical conversion into formic acid, [10] photocatalytic reduction to CO, [11] and methanol steam reforming. [12] Recently,d ensity functional theory (DFT) studies on CO 2 hydrogenation over non-defective [13] and defective [14] In 2 O 3 (110) surfaces suggested that methanol is the most favorable product and that the reaction follows am echanism comprising the cyclic c...

Oxygen vacancies of zinc oxide were followed by photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopies. The green PL emission was associated with oxygen vacancies: its intensity is enhanced upon static thermal treatment under inert or under vacuum, whereas it decreases upon oxygen treatment. A unique EPR signal at g = 1.96 was measured at room temperature after thermal in situ treatment under flow of inert or oxygenated atmospheres, its double integration follows the same trends than the green PL emission and its evolution was shown to probe the oxygen vacancy concentrations. The relative concentration of the related paramagnetic species would be increased/decreased upon trapping/release of the electron associated to the formation/filling of oxygen vacancy. The influence of Ti impurities on the PL and RPE signals was investigated. Finally, it is concluded that the EPR signal is related to oxygen vacancies and its position shift could be explained by the involvement of some mixing orbitals. Thanks to static (PL and EPR) and dynamic (EPR) in situ characterizations, the conditions of formation or filling of oxygen vacancies are discussed depending of the atmosphere and temperature of the pretreatment of kadox and ex-carbonate zinc oxide. High temperature treatments, inert atmospheres, and vacuum lead to the formation of new oxygen vacancies. This process is reversible upon oxygenated atmospheres. The efficiency of such filling up depends on the temperature and starts to prevail on the oxygen vacancy formation below 500 K. It is also shown that few native oxygen vacancies can also be filled up.