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Dr Utsab Guharoy


Postgraduate Research Student
+44 (0)1483 689475
36 BC 02

Academic and research departments

Department of Chemical and Process Engineering.

My publications

Publications

Guharoy Utsab, Ramirez Reina Tomas, Gu Sai, Cai Qiong (2019)Mechanistic Insights into Selective CO2 Conversion via RWGS on Transition Metal Phosphides: A DFT Study, In: Journal of Physical Chemistry C123(37)pp. 22918-22931 American Chemical Society
Selective conversion of CO2 to CO via the reverse water gas shift (RWGS) reaction is an attractive CO2 conversion process, which may be integrated with many industrial catalytic processes such as Fischer−Tropsch synthesis to generate added value products. The development of active and cost friendly catalysts is of paramount importance. Among the available catalyst materials, transition metal phosphides (TMPs) such as MoP and Ni2P have remained unexplored in the context of the RWGS reaction. In the present work, we have employed density functional theory (DFT) to first investigate the stability and geometries of selected RWGS intermediates on the MoP (0001) surface, in comparison to the Ni2P (0001) surface. Higher adsorption energies and Bader charges are observed on MoP (0001), indicating better stability of intermediates on the MoP (0001) surface. Furthermore, mechanistic investigation using potential energy surface (PES) profiles showcased that both MoP and Ni2P were active toward RWGS reaction with the direct path (CO2* → CO* + O*) favorable on MoP (0001), whereas the COOH-mediated path (CO2* + H* → COOH*) favors Ni2P (0001) for product (CO and H2O) gas generation. Additionally, PES profiles of initial steps to CO activation revealed that direct CO decomposition to C* and O* is favored only on MoP (0001), while H-assisted CO activation is more favorable on Ni2P (0001) but could also occur on MoP (0001). Furthermore, our DFT calculations also ascertained the possibility of methane formation on Ni2P (0001) during the RWGS process, while MoP (0001) remained more selective toward CO generation.
Ramirez Reina Tomas, Guharoy Utsab, Olsson Emilia, Gu Sai, Cai Qiong Theoretical insights of Ni2P (0001) surface towards its potential applicability in CO2 conversion via dry reforming of methane, In: ACS Catalysis9(4)pp. 3487-3497 American Chemical Society
This study reports the potential application of Ni2P as highly effective catalyst for chemical CO2 recycling via dry reforming of methane (DRM). Our DFT calculations reveal that the Ni2P (0001) surface is active towards adsorption of the DRM species, with the Ni hollow site being the most energetically stable site and Ni-P and P contributes as co-adsorption sites in DRM reaction steps. Free energy analysis at 1000 K found CH-O to be the main pathway for CO formation. The competition of DRM and reverse water gas shift (RWGS) is also evidenced with the latter becoming important at relatively low reforming temperatures. Very interestingly oxygen seems to play a key role in making this surface resistant towards coking. From microkinetic analysis we have found greater oxygen surface coverage than that of carbon at high temperatures which may help to oxidize carbon deposits in continuous runs. The tolerance of Ni2P towards carbon deposition was further corroborated by DFT and micro kinetic analysis. Along with the higher probability of C oxidation we identify poor capacity of carbon diffusion on the Ni2P (0001) surface with very limited availability of C nucleation sites. Overall, this study opens new avenues for research in metal-phosphide catalysis and expands the application of these materials to CO2 conversion reactions.
Guharoy Utsab, Le Saché Estelle, Cai Qiong, Ramirez Reina Tomas, Gu Sai (2018)Understanding the role of Ni-Sn interaction to design highly effective CO2 conversion catalysts for dry reforming of methane, In: Journal of CO2 Utilization27pp. 1-10 Elsevier
CO2 reforming of methane is an effective route for carbon dioxide recycling to valuable syngas. However conventional catalysts based on Ni fail to overcome the stability requisites in terms of resistance to coking and sintering. In this scenario, the use of Sn as promoter of Ni leads to more powerful bimetallic catalysts with enhanced stability which could result in a viable implementation of the reforming technology at commercial scale. This paper uses a combined computational (DFT) and experimental approach, to address the fundamental aspects of mitigation of coke formation on the catalyst’s surface during dry reforming of methane (DRM). The DFT calculation provides fundamental insights into the DRM mechanism over the mono and bimetallic periodic model surfaces. Such information is then used to guide the design of real powder catalysts. The behaviour of the real catalysts mirrors the trends predicted by DFT. Overall the bimetallic catalysts are superior to the monometallic one in terms of long-term stability and carbon tolerance. In particular, low Sn concentration on Ni surface effectively mitigate carbon formation without compromising the CO2 conversion and the syngas production thus leading to excellent DRM catalysts. The bimetallic systems also presents higher selectivity towards syngas as reflected by both DFT and experimental data. However, Sn loading has to be carefully optimized since a relatively high amount of Sn can severely deter the catalytic performance.