TITLE : Unveiling functional catalytic surfaces based on insights from operando spectroscopy
ABSTRACT :
Efficient detection of environmental pollutants and their conversion into renewable energy sources holds the key to mitigating problems of global energy crisis and climate change [1] . Heterogeneous catalysis plays a significant role in both processes, with surface-analyte interactions deciding the fate of a certain molecular conversion. While conventional spectroscopic techniques primarily reveal the initial and final molecular states of a certain analyte (say CO or NO2), operando spectroscopy, by virtue of its real-time spectroscopic monitoring of surfaces alongside performance evaluation provides information on complex reaction intermediates deciding the course of a certain reaction [2]. This also involves identifying the crucial rate determining step (RDS) of a catalytic process, which resolves surface selectivity [3] . In this talk, I shall introduce a modified “perturbative” version of operando spectroscopy of surfaces, where helicity-resolved circularly polarized Raman spectroscopy is employed to understand real-time surface-analyte hybridization (spin-spin coupling) in NO2-OH interactions on Au@CuO gas sensors [4]. Under a Stark tuning rate of 2.5 cm-1 per kV/cm, a 14→25% change in intensity of polarized emission has been identified as hybridization of degeneracy-broken π*2px and π*2py orbitals in NO2 with p orbitals of surface hydroxyl species, during NO2→N2O conversion. Combined with operando UV-Vis studies, the roles of surface and sub-surface defects were simultaneously probed. Distributions of surface oxygen vacancies and -OH orientation were identified as crucial factors in controlling the overall reaction mechanism [4] . The methodology developed has been successfully implemented to explain NO2 reduction reaction processes on Sb single atom-MnPS3 (few layered) based hybrid materials, where the significant intermediary NOOH was generated by modulating p - p (Sb - O) orbital hybridization towards successful NH3 formation [5]. Above understanding opens a new dimension in the field of surface structure-catalytic property correlation, aiming towards advanced catalyst design.
References:
[1] Zhou, C., Beydokhti, M.T., Rammal, F. et al. Nat Catal 2025, 8, 270–281.
[2] Elger, A.-K.; Baranyai, J.; Hofmann, K.; Hess, C. ACS Sens. 2019, 4 (6), 1497– 1501.
[3] Pestman, R.; Chen, W.; Hensen, E. ACS Catal. 2019, 9, 5, 4189–4195.
[4] Chakraborty, N.; Nandy, S.; Bhattacharjee, S.; Pfeiffer, M.; Adabifiroozjaei, E.; Molina-Luna, L.; Hess, C. J. Am. Chem. Soc. 2025 (under revision)
[5] Chakraborty, N.; Bhattacharjee, S.; Ghosh, A.; Lifshitz, E.; Mondal, S. J. Mater. Chem. A 2025, 13, 16491–16507.
ABOUT THE SPEAKER :
Dr. Nirman Chakraborty completed his PhD from CSIR-Central Glass and Ceramic Research Institute, Kolkata in 2022, on surface structure-property correlation studies in sensors and heterogenous catalysis. He has carried out his postdoctoral research at the Weizmann Institute of Science (Israel) on self-assembled surface monolayers and Technion (Israel) on interfacial spin ordering and quasi-operando studies of functional 2D materials. Currently an Alexander von Humboldt postdoc fellow at the Technical University of Darmstadt, Germany, in group of Prof. Christian Hess, Dr. Chakraborty works on perturbative operando spectroscopy of catalytic surfaces to understand spin exchange mechanisms during surface-analyte hybridization and hence investigate surface selectivity. He has published in reputed SCI journals like Materials Horizons, Journal of Materials Chemistry A, Chemistry of Materials, ACS Applied materials and interfaces. His works have brought recognitions like the G C Jain Award for Best PhD thesis in Materials Science, 2022 by the Materials Research Society of India (MRSI) and the Weizmann excellence postdoctoral fellowship.
MEETING DETAILS :
Speaker: Dr. Nirman Chakraborty, Alexander von Humboldt Fellow, Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Technical University of Darmstadt, Darmstadt, Germany
Venue: A4 conference room, South Campus, IIT Mandi
Date and Time: January 27th, 2025, Tuesday | 3:00 pm (IST)