Nitish Roy | Indian institute of technology (original) (raw)

Papers by Nitish Roy

Bulletin of the Chemical Society of Japan

Bengal. He received a Ph.D. degree on facets dependent reactivity of nanostructured materials fro... more Bengal. He received a Ph.D. degree on facets dependent reactivity of nanostructured materials from the Indian Institute of Technology, Kharagpur in 2014. After his Ph.D., he joined the Tokyo University of Science, Noda Campus as a Postdoctoral Fellow working under Prof. Akira Fujishima on diamond photoelectrochemistry for CO 2 reduction.

Catalysts

Titanium dioxide (TiO2) has been widely used as a catalyst material in different applications suc... more Titanium dioxide (TiO2) has been widely used as a catalyst material in different applications such as photocatalysis, solar cells, supercapacitor, and hydrogen production, due to its better chemical stability, high redox potential, wide band gap, and eco-friendly nature. In this work TiO2 thin films have been deposited onto both glass and silicon substrates by the atmospheric pressure plasma jet (APPJ) technique. The structure and morphological properties of TiO2 thin films are studied using different characterization techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and field emission scanning electron microscopy. XRD study reveals the bronze-phase of TiO2. The XPS study shows the presence of Ti, O, C, and N elements. The FE-SEM study shows the substrate surface is well covered with a nearly round shaped grain of different size. The optical study shows that all the deposited TiO2 thin films exhibit strong absorption in the ultravio...

RSC Advances

A mesoporous TiO2/BDD hybrid electrode showed a synergetic effect between electrochemical water t... more A mesoporous TiO2/BDD hybrid electrode showed a synergetic effect between electrochemical water treatment and photocatalytic water treatment.

Journal of Applied Electrochemistry

Molecules

There is a need for highly efficient photocatalysts, particularly for water purification. In this... more There is a need for highly efficient photocatalysts, particularly for water purification. In this study, we fabricated a mesoporous TiO2 thin film on a boron-doped diamond (BDD) layer by a surfactant-assisted sol-gel method, in which self-assembled amphiphilic surfactant micelles were used as an organic template. Scanning electron microscopy revealed uniform mesopores, approximately 20 nm in diameter, that were hexagonally packed in the TiO2 thin film. Wide-angle X-ray diffraction and Raman spectroscopy clarified that the framework crystallized in the anatase phase. Current–voltage (I–V) measurements showed rectification features at the TiO2/BDD heterojunction, confirming that a p–n hetero-interface formed. The as-synthesized mesoporous TiO2/BDD worked well as a photocatalyst, even with a small volume of TiO2 (15 mm × 15 mm × c.a. 1.5 µm in thickness). The use of deep UV light (λ = 222 nm) as a light source was necessary to enhance photocatalytic activity, due to photo-excitation oc...

ACS Omega

Effective and facile electrochemical oxidation of chemical fuels is pivotal for fuel cell applica... more Effective and facile electrochemical oxidation of chemical fuels is pivotal for fuel cell applications. Herein, we report the electrocatalytic oxidation of hydrazine on a citratecapped Au-TiO 2-modified glassy carbon electrode, which follows two different oxidation paths. These two pathways of hydrazine oxidation are ascribed to occur on Au and the activated TiO 2 surface of the Au-TiO 2 hybrid electrocatalyst. This activation was achieved through molecular capping of the Au-TiO 2 surface by citrate, which leads to favorable hydrazine oxidation with a lower Tafel slope compared to that of the clean surface of the respective materials, that is, Au and TiO 2 .

Scientific Reports, 2016

Competitive hydrogen evolution and multiple proton-coupled electron transfer reactions limit phot... more Competitive hydrogen evolution and multiple proton-coupled electron transfer reactions limit photoelectrochemical CO 2 reduction in aqueous electrolyte. Here, oxygen-terminated lightly borondoped diamond (BDD L) thin films were synthesized as a semiconductor electron source to accelerate CO 2 reduction. However, BDD L alone could not stabilize the intermediates of CO 2 reduction, yielding a negligible amount of reduction products. Silver nanoparticles were then deposited on BDD L because of their selective electrochemical CO 2 reduction ability. Excellent selectivity (estimated CO:H 2 mass ratio of 318:1) and recyclability (stable for five cycles of 3 h each) for photoelectrochemical CO 2 reduction were obtained for the optimum silver nanoparticle-modified BDD L electrode at −1.1 V vs. RHE under 222-nm irradiation. The high efficiency and stability of this catalyst are ascribed to the in situ photoactivation of the BDD L surface during the photoelectrochemical reaction. The present work reveals the potential of BDD L as a high-energy electron source for use with co-catalysts in photochemical conversion.

Photoelectrochemical Solar Fuel Production, 2016

ACS applied materials & interfaces, Jan 27, 2016

Semiconductor photocatalysis driven by electron/hole has begun a new era in the field of solar en... more Semiconductor photocatalysis driven by electron/hole has begun a new era in the field of solar energy conversion and storage. Here we report the fabrication and optimization of TiO2/BDD p-n heterojunction photoelectrode using p-type boron doped diamond (BDD) and n-type TiO2 which shows enhanced photoelectrochemical activity. A p-type BDD was first deposited on Si substrate by microwave plasma chemical vapor deposition (MPCVD) method and then n-type TiO2 was sputter coated on top of BDD grains for different durations. The microstructural studies reveal a uniform disposition of anatase TiO2 and its thickness can be tuned by varying the sputtering time. The formation of p-n heterojunction was confirmed through I-V measurement. A remarkable rectification property of 63773 at 5 V with very small leakage current indicates achieving a superior, uniform and precise p-n junction at TiO2 sputtering time of 90 min. This suitably formed p-n heterojunction electrode is found to show 1.6 fold hig...

The Journal of Physical Chemistry C, 2015

Semiconductor Science and Technology, 2015

The Journal of Physical Chemistry C, 2014

Electrochemical oxygen evolution reaction (OER) involves high overpotential at the oxygen evolvin... more Electrochemical oxygen evolution reaction (OER) involves high overpotential at the oxygen evolving electrode and thereby suffers significant energy loss in the proton exchange membrane water electrolyzer. To reduce the OER overpotential, precious ruthenium and iridium oxides are most commonly used as anode electrocatalyst. Here we report marked reduction in overpotential for the OER using transition metal (TM) doped TiO 2 nanocrystals (NCs). This reduction in overpotential is attributed to dorbitals splitting of the doped TMs in the TM-doped TiO 2 NCs and their interactions with the oxyradicals (intermediates of OER) facilitating the OER. The d-orbital spitting of TMs in TM-doped TiO 2 NCs is evident from the change in original pearl white color of undoped TiO 2 NCs and UV−vis absorption spectra.

CrystEngComm, 2014

Visible light irradiation induces recrystallization of Cu2O cubes to [010] growth-directed CuO na... more Visible light irradiation induces recrystallization of Cu2O cubes to [010] growth-directed CuO nanoribbons in water due to the creation of active ˙OH and ˙O2− species and outward Cu diffusion along unstable {010} facets.

ACS applied materials & interfaces, Jan 8, 2014

The exposed facets of a crystal are known to be one of the key factors to its physical, chemical ... more The exposed facets of a crystal are known to be one of the key factors to its physical, chemical and electronic properties. Herein, we demonstrate the role of amines on the controlled synthesis of TiO2 nanocrystals (NCs) with diverse shapes and different exposed facets. The chemical, physical and electronic properties of the as-synthesized TiO2 NCs were evaluated and their photoredox activity was tested. It was found that the intrinsic photoredox activity of TiO2 NCs can be enhanced by controlling the chemical environment of the surface, i.e.; through morphology evolution. In particular, the rod shape TiO2 NCs with ∼25% of {101} and ∼75% of {100}/{010} exposed facets show 3.7 and 3.1 times higher photocatalytic activity than that of commercial Degussa P25 TiO2 toward the degradation of methyl orange and methylene blue, respectively. The higher activity of the rod shape TiO2 NCs is ascribed to the facetsphilic nature of the photogenerated carriers within the NCs. The photocatalytic a...

ACS Nano, 2013

Controlled crystal growth determines the shape, size, and exposed facets of a crystal, which usua... more Controlled crystal growth determines the shape, size, and exposed facets of a crystal, which usually has different surface physicochemical properties. Herein we report the size and facet control synthesis of anatase TiO2 nanocrystals (NCs). The exposed facets are found to play a crucial role in the photocatalytic activity of TiO2 NCs. This is due to the known preferential flow of photogenerated carriers to the specific facets. Although, in recent years, the main focus has been on increasing the surface area of high-energy exposed facets such as {001} and {100} to improve the photocatalytic activity, here we demonstrate that the presence of both the high-energy {001} oxidative and low-energy {101} reductive facets in an optimum ratio is necessary to reduce the charge recombination and thereby enhance photocatalytic activity of TiO2 NCs.