Faculty Publications

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Author: search.filters.author.Roy, S.Subject: search.filters.subject.Electrocatalytic reduction

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    Structure-sensitive electrocatalytic reduction of co2 to methanol over carbon-supported intermetallic ptzn nano-alloys
    (American Chemical Society service@acs.org, 2020) Payra, S.; Shenoy, S.; Chakraborty, C.; Tarafder, K.; Roy, S.
    The electrochemical reduction of CO2 (CO2RR) to produce valuable synthetic fuel like CH3OH not only mitigates the accumulated greenhouse gas from the environment but is also a promising direction toward attenuating our continuous reliance on fossil fuels. However, CO2RR to yield CH3OH suffers because of large overpotential, competitive H2 evolution reaction (HER), and poor product selectivity. In this regard, intermetallic alloy catalysts open up a wide possibility of fine-tuning the electronic property and attain appropriate structures that facilitate selective CO2RR. Here, we report for the first time the CO2RR over carbon-supported PtZn nano-alloys and probed the crucial role of structures and interfaces as active sites. PtZn/C, Pt3Zn/C, and PtxZn/C (1 < x < 3) synthesized from the metal-organic framework material were characterized structurally and morphologically. The catalysts demonstrated structure dependency toward CH3OH selectivity, as the mixed-phase PtxZn/C outperformed the phase-pure PtZn/C and Pt3Zn/C. The structure-dependent reaction mechanism and the kinetics were elucidated over the synthesized catalysts with the help of detail experiments and associated density functional theory calculations. Results showed that in spite of low electrochemically active surface area, PtxZn could not only have facilitated the single electron transfer to adsorbed CO2 but also showed better binding of the intermediate CO2 •- over its surface. Moreover, the lower bond energy between the mixed-phase surface and -OCH3 compared to the phase-pure catalysts has enabled higher CH3OH selectivity over PtxZn. This work opens a wide possibility of studying the role of interfaces between phase-pure nano-alloys toward CO2RR. © 2020 American Chemical Society
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    Photo- and Electrocatalytic Reduction of CO2 over Metal-Organic Frameworks and Their Derived Oxides: A Correlation of the Reaction Mechanism with the Electronic Structure
    (American Chemical Society, 2022) Payra, S.; Ray, S.; Sharma, R.; Tarafder, K.; Mohanty, P.; Roy, S.
    A Ce/Ti-based bimetallic 2-aminoterephthalate metal-organic framework (MOF) was synthesized and evaluated for photocatalytic reduction of CO2 in comparison with an isoreticular pristine monometallic Ce-terephthalate MOF. Owing to highly selective CO2 adsorption capability, optimized band gaps, higher flux of photogenerated electron-hole pairs, and a lower rate of recombination, this material exhibited better photocatalytic reduction of CO2 and lower hydrogen evolution compared to Ce-terephthalate. Thorough probing of the surface and electronic structure inferred that the reducibility of Ce4+ to Ce3+ was due to the introduction of an amine functional group into the linker, and low-lying Ti(3d) orbitals in Ce/Ti-2-aminoterephthalate facilitated the photoreduction reaction. Both the MOFs were calcined to their respective oxides of Ce1-xTixO2 and CeO2, and the electrocatalytic reduction of CO2 was performed over the oxidic materials. In contrast to the photocatalytic reaction mechanism, the lattice substitution of Ti in the CeO2 fluorite cubic structure showed a better hydrogen evolution reaction and consequently, poorer electroreduction of CO2 compared to pristine CeO2. Density functional theory calculations of the competitive hydrogen evolution reaction on the MOF and the oxide surfaces corroborated the experimental findings. © 2022 American Chemical Society.
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    Unprecedented Electroreduction of CO2over Metal Organic Framework-Derived Intermetallic Nano-Alloy Cu0.85Ni0.15/C
    (American Chemical Society, 2022) Payra, S.; Devaraj, N.; Tarafder, K.; Roy, S.
    Designing suitable catalysts for efficient and selective electrocatalytic reduction of CO2 is a need of the hour, and in this regard, the well-defined, highly dispersed active metal centers can be a trendsetting research endeavor toward CO2 electroreduction due to the maximum atom utilization and unique electronic structure. This study describes the synthesis and electrocatalytic CO2 reduction activity of atomistically dispersed Cu/C and Ni/C and the intermetallic nano-alloy Cu0.85 Ni0.15 /C. The catalysts were synthesized from the corresponding MOF precursors. The successful synthesis of the monometallic and intermetallic nano-alloys was established from structural, surface morphological, and electronic properties. Cu0.85 Ni0.15 /C exhibited an unprecedented electrocatalytic reduction of CO2 with a high selectivity and high faradaic efficiency toward CH3 OH. The kinetic studies and the first-principles calculations elucidated the intricate mechanism and the superior activity of electrocatalytic reduction of CO2 over the intermetallic Cu0.85 Ni0.15 /C catalyst. © 2022 American Chemical Society. All rights reserved.