Somnath C. Roy

Bio: Somnath C. Roy is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Materials science & Thin film. The author has an hindex of 30, co-authored 143 publications receiving 3992 citations. Previous affiliations of Somnath C. Roy include Instituto Superior Técnico & Indian Institute of Technology Kharagpur.

Probing the charge recombination in rGO decorated mixed phase (anatase-rutile) TiO2 multi-leg nanotubes

Abstract: Recombination of photo-generated charges is one of the most significant challenges in designing efficient photo-anode for photo electrochemical water oxidation. In the case of TiO2, mixed phase (anatase-rutile) junctions often shown to be more effective in suppressing electron-hole recombination compared to a single (anatase or rutile) phase. Here, we report the study of bulk and surface recombination process in TiO2 multi-leg nanotube (MLNTs) anatase-rutile (A-R) junctions decorated with reduced graphene oxide (rGO) layers, through an analysis of the photo-current and impedance characteristics. To quantify the charge transport/transfer process involved in these junctions, holes arriving at the interface of semiconductor/electrolyte were collected by adding H2O2 to the electrolyte. This enabled us to interpret the bulk and surface recombination process involved in anatase/rutile/rGO junctions for photo-electrochemical water oxidation. We correlated this quantification to the electrochemical impedance spectroscopy (EIS) measurements, and showed that in anatase/rutile junction the increase in PEC performance was due to suppression in electron-hole recombination rate at the surface states that effectively enhances the hole transfer rate to the electrolyte. On the other hand, in rGO wrapped A-R MLNTs junction it was due to both phenomenon i.e decrease in bulk recombination rate as well as increase in hole transfer rate to the electrolyte at the semiconductor/electrolyte interface.

Solvothermal Processing of Amorphous TiO2 Nanotube Arrays: Achieving Crystallinity at a Lower Thermal Budget

Abstract: Highly aligned, vertically oriented TiO2 nanotube arrays formed by electrochemical anodization have been extensively investigated in the recent times because of various potential applications such as in solar cells, hydrogen generation, CO2 reduction, gas sensors and as biocompatible material. The as prepared nanotubes, however, are amorphous and require a thermal annealing process to achieve the desired crystallographic phase. Here we report a simple solvothermal technique by which the crystallinity of the nanotube arrays can be tailored at temperatures around 200 °C to achieve the anatase phase without destroying the tubular morphology. In this alcohol-based solvothermal process, the crystallinity can be enhanced by changing the solvent from methanol to isobutanol and the sample treated with isobutanol for 2 h shows crystallinity and strain comparable to that of a sample annealed in a conventional furnace at 550 °C. A mechanism for the solvothermal crystallization and the enhancement of crystallinity ha...

Enhanced methane yield by photoreduction of CO2 at moderate temperature and pressure using Pt coated, graphene oxide wrapped TiO2 nanotubes

Abstract: Photocatalytic conversion of CO2 into hydrocarbons is one of the most sought-after approaches as it not only helps for its mitigation and utilization but does so through the renewable solar energy. Development of suitable materials and protocols to achieve better efficiency in photoconversion has been projected as one of the grand challenges in the 21st century. However, the stability of CO2 leads to a high thermodynamic barrier for its conversion into value added chemicals. In this work, we report the design and fabrication of novel three-component nanostructured photocatalyst material comprising TiO2 nanotube arrays, reduced graphene oxide and Pt nanoparticles. TiO2 nanotubes fabricated by electrochemical anodization are functionalized by chemically deposited graphene oxide layers and Pt particles deposited by sputtering technique. The photocatalysts are characterized for the crystallinity, morphology, and composition through XRD, FE-SEM and EDAX studies. Such a combination ensures easier separation of photogenerated charges as well as better catalytic activity. Further, the photoreduction experiments are carried out at moderately higher temperature of about 80 °C and at about 1.8 atm pressure in an indigenously designed batch reactor to partly overcome the thermodynamic barrier. We have achieved a high methane generation rate of about 3.42 mmol/g/hr. The possible reaction mechanisms are discussed.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Nano‐photocatalytic Materials: Possibilities and Challenges

Abstract: Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.

Photocatalytic reduction of CO2 on TiO2 and other semiconductors.

Abstract: Rising atmospheric levels of carbon dioxide and the depletion of fossil fuel reserves raise serious concerns about the ensuing effects on the global climate and future energy supply. Utilizing the abundant solar energy to convert CO2 into fuels such as methane or methanol could address both problems simultaneously as well as provide a convenient means of energy storage. In this Review, current approaches for the heterogeneous photocatalytic reduction of CO2 on TiO2 and other metal oxide, oxynitride, sulfide, and phosphide semiconductors are presented. Research in this field is focused primarily on the development of novel nanostructured photocatalytic materials and on the investigation of the mechanism of the process, from light absorption through charge separation and transport to CO2 reduction pathways. The measures used to quantify the efficiency of the process are also discussed in detail.

An overview of current status of carbon dioxide capture and storage technologies

Abstract: Global warming and climate change concerns have triggered global efforts to reduce the concentration of atmospheric carbon dioxide (CO2). Carbon dioxide capture and storage (CCS) is considered a crucial strategy for meeting CO2 emission reduction targets. In this paper, various aspects of CCS are reviewed and discussed including the state of the art technologies for CO2 capture, separation, transport, storage, leakage, monitoring, and life cycle analysis. The selection of specific CO2 capture technology heavily depends on the type of CO2 generating plant and fuel used. Among those CO2 separation processes, absorption is the most mature and commonly adopted due to its higher efficiency and lower cost. Pipeline is considered to be the most viable solution for large volume of CO2 transport. Among those geological formations for CO2 storage, enhanced oil recovery is mature and has been practiced for many years but its economical viability for anthropogenic sources needs to be demonstrated. There are growing interests in CO2 storage in saline aquifers due to their enormous potential storage capacity and several projects are in the pipeline for demonstration of its viability. There are multiple hurdles to CCS deployment including the absence of a clear business case for CCS investment and the absence of robust economic incentives to support the additional high capital and operating costs of the whole CCS process.