Faculty Directory

Ph.D. positions are available in my group for students with CSIR-NET-JRF, UGC-NET-JRF or any other national fellowship.

Contact the PI at rsdey@inst.ac.in for more details.

Electrochemistry of nanomaterials

Inorganic and materials chemistry

Electrochemical N2 fixation to ammonia and urea

Electrochemical CO2 reduction

Electrocatalysis: water splitting and oxygen reduction reactions

Energy conversion and storage

Supercapacitor, on-chip microcapacitor, Li-ion battery, integrated self-powered storage device

Electrochemistry of 2D nanomaterials such as graphene and Mxene

Hybrid energy technology: solar-powered H2 production

Ultrafine mix-phase SnO-SnO2 nanoparticles anchored on reduced graphene oxide boost reversible Li-ion storage capacity beyond theoretical limit. (ACS Nano, 2022, 16, 15358–15368)

Tin-based materials with high specific capacity have been studied as high-performance anodes for Li-ion storage devices. Herein, a mix-phase structure of SnO-SnO2@rGO (rGO = reduced graphene oxide) was designed and prepared via a simple chemical method, which leads to the growth of tiny nanoparticles of a mixture of two different tin oxide phases on the crumbled graphene nanosheets. The three-dimensional structure of graphene forms the conductive framework. The as-prepared mix phase SnO-SnO2@rGO exhibits a large Brunauer-Emmett-Teller surface area of 255 m2 g–1 and an excellent ionic diffusion rate. When the resulting mix-phase material was examined for Li-ion battery anode application, the SnO-SnO2@rGO was noted to deliver an ultrahigh reversible capacity of 2604 mA h g–1 at a current density of 0.1 A g–1. It also exhibited superior rate capabilities and more than 82% retention of capacity after 150 charge–discharge cycles at 0.1 A g–1, lasting until 500 cycles at 1 A g–1 with very good retention of the initial capacity. Owing to the uniform defects on the rGO matrix, the formation of LiOH upon lithiation has been suggested to be the primary cause of this very high reversible capacity, which is beyond the theoretical limit. A Li-ion full cell was assembled using LiNi0.5Mn0.3Co0.2O2 (NMC-532) as a high-capacity cathodic counterpart, which showed a very high reversible capacity of 570 mA h g–1 (based on the anode weight) at an applied current density of 0.1 A g–1 with more than 50% retention of capacity after 100 cycles. This work offers a favorable design of electrode material, namely, mix-phase tin oxide-nanocarbon matrix, exhibiting adequate electrochemical performance for Li storage applications.

Engineering hydrophobic-aerophilic interface to boost N2 diffusion and reduction through functionalization of fluorine in second coordination sphere. (Chemical Science, 2023, 14, 8936 - 8945)

Ammonia is a crucial biochemical raw material for nitrogen containing fertilizers and a hydrogen energy carrier obtained from renewable energy sources. Electrocatalytic ammonia synthesis is a renewable and less-energy intensive way as compared to the conventional Haber–Bosch process. The electrochemical nitrogen reduction reaction (eNRR) is sluggish, primarily due to the deceleration by slow N2 diffusion, giving rise to competitive hydrogen evolution reaction (HER). Herein, we have engineered a catalyst to have hydrophobic and aerophilic nature via fluorinated copper phthalocyanine (F-CuPc) grafted with graphene to form a hybrid electrocatalyst, F-CuPc-G. The chemically functionalized fluorine moieties are present in the second coordination sphere, where it forms a three-phase interface. The hydrophobic layer of the catalyst fosters the diffusion of N2 molecules and the aerophilic characteristic helps N2 adsorption, which can effectively suppress the HER. The active metal center is present in the primary sphere available for the NRR with a viable amount of H+ to achieve a substantially high faradaic efficiency (FE) of 49.3% at −0.3 V vs. RHE. DFT calculations were performed to find out the rate determining step and to explore the full energy pathway. A DFT study indicates that the NRR process follows an alternating pathway, which was further supported by an in situ FTIR study by isolating the intermediates. This work provides insights into designing a catalyst with hydrophobic moieties in the second coordination sphere together with the aerophilic nature of the catalyst that helps to improve the overall FE of the NRR by eliminating the HER.

Lewis acid-dominated aqueous electrolyte acting as co-catalyst and overcoming N₂ activation issues on catalyst surface (Proceedings of the National Academy of Sciences (PNAS), 2022, 119 (33) e2204638119)

The electrochemical ammonia synthesis is majorly limited by the poor solubility of N2 in the aqueous electrolyte environment, besides the competitive hydrogen evolution reaction. In an attempt to solve these issues, the “ambient” conditions are mostly overlooked. This work is an approach to examine the long-standing issues about the solubility of N2 in aqueous medium and achievement of industrial-scale production rate of ammonia by nitrogen reduction reaction (NRR) at ambient condition. Mechanistic investigation shows that Lewis acid (BF3) has the capability to hold N2 by forming a Lewis acid-base adduct, which further adsorbs on catalyst surface by a push-pull electronic effect. Therefore, this report may open new vistas to studying and understanding the role of the NRR in aqueous medium.

Ultralong cycle life and outstanding capacitive performance of 10.8 V metal-free micro-supercapacitor with highly conducting and robust laser-irradiated graphene for integrated storage device (Energy Environ. Sci., 2019, 12, 2507-2517)

Dr. Ramendra S. Dey and his research team have recently shown that interconnected porous graphene plays a crucial role as supercapacitive material as well as a current collector in developing metal free microsupercapacitor (MSC) because of its unique structure and superior conductivity. Electrochemical reduction followed by use of a laser irradiation method shows advances for the fabrication of the conductive graphene-based robust device. The laser irradiation method is capable of healing the defects with fused interconnected sheets, as a result, high conductivity and improved crystallinity of the laser irradiated graphene (LIG) sample is achieved. The LIG film on a flexible substrate was patterned with the aim to develop an on-chip flexible MSC, which offers a large cell voltage of 10.8 V and 100% retention of the initial capacitance after 100 000 continuous cycles. The array of LIG-MSC was integrated with a commercial solar cell module for hybrid energy harvesting and as a storage device. This study provides an effective strategy to build a metal-free supercapacitor with exceptional cycle life and facilitates progress towards self-sustainable energy in the future.