Faculty Publications
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Item The structural and surface modification of zeolitic imidazolate frameworks towards reduction of encapsulated CO2(Royal Society of Chemistry, 2018) Payra, S.; Challagulla, S.; Reddy, R.R.; Chakraborty, C.; Tarafder, K.; Ghosh, B.; Roy, S.ZIF-8, a metal organic framework with a sodalite topological structure, is a widely studied crystalline microporous material due to its thermal and chemical stability. However, the existing studies mostly focus on understanding the porosity and bulk structure of ZIF-8, ignoring the external facets of the porous crystal, which are the first points of interaction between adsorbent and guest adsorbate. This paper reports on understanding the preferential exposure of thermodynamically stable and unstable facets as a function of synthetic methodology. The comprehensive and combinatorial investigation of experimental and theoretical studies shows that the high energy {112} facets of ZIF-8 efficiently reduce the encapsulated CO2 to fuel compared to the {011} facets. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item The role of synthesis vis-à-vis the oxygen vacancies of Co3O4 in the oxygen evolution reaction(Royal Society of Chemistry, 2022) Roy, S.; Devaraj, N.; Tarafder, K.; Chakraborty, C.; Roy, S.The oxygen evolution reaction over oxide vacancy-induced spinel Co3O4 is a topic of tremendous scientific attention owing to the favourable adsorption of water, as also shown here through DFT calculations. However, the inclusion of an optimum amount of oxygen-ion vacancies at the surface and in the bulk of Co3O4 remains a synthetic challenge in order to enhance the efficacy of the oxygen evolution reaction. Here, we have attempted a single-step scalable approach of solution combustion synthesis to incorporate the oxide ion vacancies in high-surface-area Co3O4. To benchmark the catalyst, we also synthesized Co3O4 using elevated-temperature calcination routes. Detailed structural and surface analyses revealed the significant presence of oxide ion vacancies in the combustion-synthesized material. The solution combustion synthesized Co3O4 due to the presence of oxygen-ion vacancies exhibited an excellent oxygen evolution reactivity with a lower overpotential and higher current density compared with the other Co3O4 materials synthesized using calcination routes. Tafel slope calculations indicated that the formation of surface hydroxyl species through water dissociation over the oxide ion vacancies is the rate-determining step of the overall reaction. The mechanistic role of the oxygen-ion vacancies in the oxygen evolution reaction was further explored via DFT studies. © 2022 The Royal Society of Chemistry