We investigate the chemical and structural dynamics at the interface of In2O3/m-ZrO2and their consequences on the CO2hydrogenation reaction (CO2HR) under reaction conditions. While acting to enrich CO2, monoclinic zirconia (m-ZrO2) was also found to serve as a chemical and structural modifier of In2O3that directly governs the outcome of the CO2HR. These modifying effects include the following: (1) Under reaction conditions (above 623 K), partially reduced In2O3, i.e., InOx(0 < x < 1.5), was found to migrate in and out of the subsurface of m-ZrO2in a semireversible manner, where m-ZrO2accommodates and stabilizes InOxby serving as a reservoir. The decreased concentration of surface InOxunder elevated temperatures coincides with significantly decreased selectivity toward methanol and a sharp increase of the reverse water-gas shift reaction. The reconstruction-induced variation of InOxconcentration appears to be one of the most important factors contributing to the altered catalytic performance of CO2HR at different reaction conditions. (2) The strong interactions and reactions between m-ZrO2and In2O3result in the activation of a pool of In-O bonds at the In2O3/m-ZrO2interface to form oxygen vacancies. On the other hand, the high dispersity of In2O3nanostructures onto m-ZrO2prevents their over-reduction under catalytically relevant conditions (up to 673 K), when bare In2O3is unavoidably reduced into the metallic phase (In0). The relationship between the extent of reduction of In2O3and catalytic performance (CO2conversion, CH3OH selectivity, or yield of CH3OH) suggests the presence of an optimum coverage of surface InOxand oxygen vacancies under reaction conditions. The conventional model that links catalytic performance solely to the coverage of oxygen vacancies appears invalid in the present case. In situ analysis also allows the observation of surface reaction intermediates and their interconversions, including the reduction of CO3∗ into formate, a precursor for the formation of methanol and CO. The combinative ex situ and in situ study sheds light on the reaction mechanism of the CO2HR on In2O3/m-ZrO2-based catalysts. Our findings on the large-scale surface reconstructions, support effect, and the reaction mechanism of In2O3/m-ZrO2for CO2HR may apply to other related metal oxide catalyzed CO2reduction reactions.

Efforts to map atomic-scale chemistry at low doses with minimal noise using electron microscopes are fundamentally limited by inelastic interactions. Here, fused multi-modal electron microscopy offers high signal-to-noise ratio (SNR) recovery of material chemistry at nano- and atomic-resolution by coupling correlated information encoded within both elastic scattering (high-angle annular dark-field (HAADF)) and inelastic spectroscopic signals (electron energy loss (EELS) or energy-dispersive x-ray (EDX)). By linking these simultaneously acquired signals, or modalities, the chemical distribution within nanomaterials can be imaged at significantly lower doses with existing detector hardware. In many cases, the dose requirements can be reduced by over one order of magnitude. This high SNR recovery of chemistry is tested against simulated and experimental atomic resolution data of heterogeneous nanomaterials.

Measuring the three-dimensional (3D) distribution of chemistry in nanoscale matter is a longstanding challenge for metrological science. The inelastic scattering events required for 3D chemical imaging are too rare, requiring high beam exposure that destroys the specimen before an experiment is completed. Even larger doses are required to achieve high resolution. Thus, chemical mapping in 3D has been unachievable except at lower resolution with the most radiation-hard materials. Here, high-resolution 3D chemical imaging is achieved near or below one-nanometer resolution in an Au-Fe₃O₄ metamaterial within an organic ligand matrix, Co₃O₄-Mn₃O₄ core-shell nanocrystals, and ZnS-Cu_0.64S_0.36 nanomaterial using fused multi-modal electron tomography. Multi-modal data fusion enables high-resolution chemical tomography often with 99% less dose by linking information encoded within both elastic (HAADF) and inelastic (EDX/EELS) signals. We thus demonstrate that sub-nanometer 3D resolution of chemistry is measurable for a broad class of geometrically and compositionally complex materials.