The alarming number of loss of life and healthy life years due to indoor air pollution is a growing concern amongst the emerging economies. Typically, indoor air pollutants involve carbon monoxide, nitrogen dioxide, and a host of volatile organic compounds including formaldehyde, acetaldehyde, methanol, toluene, and acetone. A common challenge encountered during the oxidation of these molecules at low temperature is surface poisoning. Formation of strongly binding reaction intermediates limits the usage of the catalyst. Common reaction intermediates encountered during these reactions include acetate, formate, and carbonate, which are also key intermediates in methane activation, CO hydrogenation, and CO2 reduction. Water, being ubiquitously present in the indoor atmosphere, plays a crucial role in the oxidative chemistry for elimination of such small molecules. In heterogeneous catalysis, water can play multiple roles in aiding the conversion of reaction intermediates via competitive adsorption, solvation effect, renewal of surface hydroxyls, as a H-transfer mediator, or the formation of strongly oxidizing hydroperoxyl (OOH) species. Using a combined experimental and theoretical framework with plug flow reactor, in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and Density Functional Theory (DFT), adsorption and oxidation of such small molecules on oxides surfaces is explored. The role of water and adsorbed oxygen is evaluated at different surface coverages of the adsorbates. The nature of surface poisoning and renewal is discussed using a descriptor-based methodology. Using this framework, strategies for complete oxidation of small molecules at low temperatures are suggested.

Role of water in oxidation of small molecules: Insights from in-situ spectroscopy

256th National Meeting (2018)

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