Department of Chemistry

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Author: search.filters.author.Basu, Mrinmoyee

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    Sulfur/nitrogen-codoped carbon-dot-modified wo3 nanosheets toward enhanced charge-carrier separation in a saline water-splitting reaction
    (ACS, 2023-11) Basu, Mrinmoyee
    Hydrogen (H2) is considered to be a future fuel because of its high energy density and could replace fossil fuels. It can be produced in a greener way by using abundant solar light and saline water and applying a photoelectrochemical (PEC) pathway. To produce green H2, WO3 2D nanosheets are developed, and their performance in saline water splitting is studied under PEC conditions. WO3 is very efficient in absorbing visible light from solar irradiation; however, it suffers from low charge-transfer rates, which inhibits its PEC performance. To increase the charge transportation ability, WO3 is sensitized with sulfur/nitrogen-codoped carbon dots (SNCDs). Impedance analysis indicates an enhanced charge transportation ability of the formed heterostructure. The best-obtained heterostructure of WO3 and SNCDs exhibits nearly 1.62 times more photocurrent density than bare WO3. Bare WO3 nanosheets can produce a photocurrent density of 1.59 mA/cm2 at 1.39 V vs Ag/AgCl. The best-obtained heterostructure of WO3 and SNCDs can produce photocurrent density of 2.57 mA/cm2 at 1.39 V vs Ag/AgCl. A type II staggered heterostructure of WO3/SNCDs leads to improved PEC activity. Enhanced carrier density and lowered charge-transfer resistances are observed from Mott–Schottky and PEC impedance analyses, respectively. The carrier density increases nearly 84 times in the heterostructure. The heterostructure exhibits effective photostability under uninterrupted illumination for 2 h.
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    Surface modifications of a vertically grown nanostructure for boosting photoelectrochemical water-splitting performance
    (ACS, 2024-04) Basu, Mrinmoyee
    Photoelectrochemical (PEC) water splitting is a promising approach for sustainable hydrogen production, driven by sunlight. To enhance the efficiency of PEC water-splitting systems, the development of efficient nanomaterials and architectures is crucial. Vertically grown nanostructures have emerged as a promising strategy to address several limitations of conventionally used PEC materials. Vertically grown architectures of nanomaterials offer various advantages such as increased light absorption by multiple reflections and scattering inside the material, decoupling in the direction of charge transfer and light absorption, maximizing the surface-area-to-volume ratio, which increases the electrode–electrolyte interface. Further heterostructure formation of these architectures can help to regulate the optoelectronic properties, which may help in enhancing the PEC performance. Heterostructure formation may involve different materials that absorb light at different wavelengths with favorable band positions. The process of heterostructure formation involves cocatalyst decoration, sensitization with different materials like quantum dots, plasmonic nanoparticles, etc. By carefully engineering the heterostructure composition and morphology, significant improvements can be achieved in the PEC performance, such as enhanced photocurrent density, extended photostability, and reduced onset potentials. The development of several advanced chemical and physical techniques, such as chemical vapor deposition, electrodeposition, hydrothermal, microwave, atomic layer deposition, etc., has enabled precise control over the heterostructure dimensions and composition, leading to desirable optoelectronic properties and optimized performance. In this Spotlight on Applications, we highlight advancements of vertically grown heterostructures for PEC water splitting. The integration of vertically aligned nanomaterials with optimized interfaces offers a promising pathway for the development of efficient and stable PEC water-splitting devices, paving the way toward sustainable hydrogen production from solar energy.
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    AU nanoparticles on in2s3/in2o3 nanopyramids increase photoanodic activity in photoelectrochemical water splitting
    (ACS, 2024-07) Basu, Mrinmoyee
    To fulfill the increasing energy demand, photoelectrochemical (PEC) water splitting is an effective approach. For that, it is very important to give rise to efficient photoelectrodes for the PEC water splitting reaction as the anodic reaction is sluggish, and because of that the overall efficiency remains obstructed. In this context, In2S3/In2O3 nanopyramids with exposed (111) facets are developed following a simple hydrothermal method. Further, the effect of Au plasmonic nanoparticles (NPs) on the In2S3/In2O3 nanopyramid surface is investigated. Au NPs are decorated on In2S3/In2O3 nanopyramids by the thermal reduction method. The dipping time of In2S3/In2O3 in a Au-precursor solution is varied to alter the loading amount of Au. Au NPs enhance the light absorption of In2S3/In2O3 nanopyramids effectively from 600 to 800 nm. Furthermore, in the presence of Au NPs, carrier concentration is enhanced at the same time charge as transportation ability is also enhanced at the interface. The optimum decoration of Au NPs helps to achieve the efficient PEC activity. The best obtained In2S3/In2O3/Au in this study shows enhancement in photocurrent density by generating 5.16 mA/cm2 photocurrent density, which is nearly 3.66 times higher compared to that of In2S3/In2O3 at an applied potential of 0.599 V vs Ag/AgCl. Decoration of Au NPs also leads to a 2.6-fold higher carrier density and cathodic shift in onset potential. In2S3/In2O3/Au achieves a maximum photoconversion efficiency of nearly 1.18% at 0.26 V vs Ag/AgCl in 0.5 M Na2SO4 electrolyte. The In2S3/In2O3/Au nanostructure can even withstand the highly corrosive environment of 3.5% saline water. High photocurrent density of 4.52 mA/cm2 at 0.599 V vs Ag/AgCl can be generated by In2S3/In2O3/Au, where 3.5 wt % saline water is used as electrolyte. The developed photoelectrode: In2S3/In2O3–Au is capable of generating higher photocurrent at 0 V vs Ag/AgCl in 3.5% saline water compared to 0.5 M Na2SO4. Under continuous illumination for 3600 s in saline water, the stability of In2S3/In2O3/Au is observed.
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    Passivation of surface states in cdin2s4 via type II heterostructure for boosting photoelectrochemical water splitting reaction
    (ACS, 2024-10) Basu, Mrinmoyee
    The visible light active semiconductors are considered as promising materials for achieving high efficiency in producing green hydrogen (H2) via the photoelectrochemical (PEC) water splitting reaction. Here CdIn2S4 (CIS) is developed as a highly visible-light-absorbing semiconductor for PEC water splitting reactions. However, CIS suffers from severe recombination of charge carriers and the photocurrent density is found to be 0.35 mA/cm2 at 1.0 V vs RHE in 0.5 M Na2SO4, despite having high visible light absorbance. The presence of surface trap states causes the Fermi level pinning effect of CIS, resulting in low surface photovoltage and PEC activity. To remove the surface trap states present in CIS, the in situ heterostructures of CdS/CIS nanosheets are developed, which induces the formation of both bulk and surface sulfur vacancies in the heterostructures. As a result, the photocurrent density is enhanced to 1.0 mA/cm2 at 1.0 V vs RHE. Further, the photocurrent density and photostability of the heterostructure are enhanced by developing the CdS/CIS/In2S3 (n-n-n) heterojunction which passivates the surface sulfur vacancies and creates the type II heterojunction. The photocurrent density is increased to 1.69 mA/cm2 at 1.0 V vs RHE. The carrier density and charge carrier conductivity are enhanced as observed from the Mott–Schottky (MS) analysis and the photoelectrochemical impedance spectroscopy (PEIS), respectively. The charge carrier density in the CdS/CIS/In2S3 heterostructure is almost 9.3 times enhanced over that of the CdS/CIS nanosheets. The charge injection and charge transportation efficiency of the heterojunction is also increased. The incident photon to current conversion efficiency (IPCE) of the CdS/CIS/In2S3 heterostructure is increased 2.21 times compared to CdS/CIS. A type II staggered heterojunction is developed between semiconductors, which enhances the overall PEC performance of the CdS/CIS/In2S3 heterostructure.
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    Doping of MoS2 by “Cu” and “V”: An Efficient Strategy for the Enhancement of Hydrogen Evolution Activity
    (ACS, 2021-04) Basu, Mrinmoyee; Pande, Surojit
    To replace Pt-based compounds in the electrocatalytic hydrogen evolution reaction (HER), MoS2 has already been established as an efficient catalyst. The electrocatalytic activity of MoS2 is further improved by tuning the morphology and the electronic structure through doping, which helps the band energy position to be modified. Presently, thin sheets of MoS2 (MoS2-TSs) are synthesized via a microwave technique. Thin sheets of MoS2 can outperform nanosheets of MoS2 in the HER. Further, the efficiency of the thin sheets is improved by doping with different metals like Cu, V, Zn, Mn, Fe, Sn, etc. “Cu”- and “V”-doped MoS2-TSs are highly efficient for the HER. At a fixed potential of −0.588 V vs RHE, Cu-doped MoS2 (Cu-MoS2-TS), V-doped MoS2 (V-MoS2-TS), and MoS2-TS can generate current densities of 327.46, 308.45, and 127.82 mA/cm2, respectively. The electrochemically active surface area increases nearly 7.7-fold and 2.5-fold for Cu-MoS2-TS and V-MoS2-TS than for MoS2-TS, respectively. Cu-MoS2-TS shows exceptionally high electrocatalytic stability up to 140 h in an acidic medium (0.5 M H2SO4). First-principles calculations using density functional theory (DFT) are performed, which are well matched with the experimental observations. DFT calculations dictate that after doping with “V” and “Cu” both valance band maxima and conduction band minima are uplifted, which indicates the higher hydrogen-ion-reducing ability of M-MoS2-TS (M = Cu, V) compared to bare MoS2-TS.
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    CdIn2.2Sy Nanosheet-Based Photoanodes for Photoelectrochemical Water Splitting
    (ACS, 2022-06) Basu, Mrinmoyee
    Photoelectrochemical water splitting is a greener approach to produce hydrogen (H2) as an efficient chemical fuel for the future with high energy density. However, it is extremely challenging to develop suitable semiconductor materials with desired efficiency and stability, which can be applied for practical applications. Looking at the theoretical efficiency and the solar spectrum, it is clear that visible-light-active semiconductors are the most appealing candidates. Herein, CdIn2.2Sy (CIS), a visible light-active semiconductor, is explored as a photoanode for PEC water splitting. The thin nanosheets of CIS are grown vertically through a hydrothermal method. These can efficiently absorb visible light through multiple reflections and scattering of light inside the material and enhance the light–matter interaction. As a result, the developed CIS thin nanosheets produce a maximum photocurrent density of 3.97 mA/cm2 at “1.6” V versus RHE under continuous back illumination. On the other hand, CIS attains a maximum photoconversion efficiency of ∼1.72% at “0.60” V versus RHE. Furthermore, to improve the efficiency and stability, “S” and “N” codoped C-dots (S, N-CDs) are adorned on the CIS photoanode. The “S” and “N” codoped C-dots and CIS form the type-II heterostructure, which efficiently boosts the charge separation and transportation of photogenerated electrons and holes. The transient decay time becomes longer in the case of heterostructure compared to bare CIS. The heterostructure generates 11.2 mA/cm2 photocurrent densities at an applied potential of “1.6” V versus RHE. At the same time, the heterostructure CIS/S, N-CDs-B achieves a ∼2.08-fold higher photoconversion efficiency compared to bare CIS nanosheets and is stable up to 1500 s under continuous back illumination. The present work offers an approach for designing an efficient and stable photoanode for PEC water splitting.
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    Nanosheets of In2S3/S-C3N4-Dots for Solar Water-Splitting in Saline Water
    (ACS, 2022-10) Basu, Mrinmoyee
    Hydrogen generation from splitting of water under the photoelectrochemical (PEC) pathway is considered as the most promising strategy for covering the upcoming fuel crisis by taking care of all environmental issues. In this context, In2S3 can be explored as it is a visible light-active semiconductor with an appropriate band alignment with the water redox potential. Herein, In2S3 nanosheets are developed by the chemical method. The nanosheets of In2S3 absorb high visible light due to the manifold inside scattering and reflection. The PEC activity of In2S3 is enhanced because of the increase in the light absorbance of the materials. In the present work, at 1.18 V versus RHE in 3.5 wt % NaCl, a maximum 2.07 mA/cm2 photocurrent density can be achieved by In2S3 nanosheets. However, In2S3 suffers strongly due to photo-corrosion. To improve the efficacy of the In2S3 nanosheets in saline water, the charge-carrier transportation ability of In2S3 is aimed to increase by decorating S-C3N4-dots on In2S3. The heterostructure of type-II is developed by sensitization of S-C3N4-dots on In2S3. It increases both the transportation of charge carriers as well as separation. In the heterostructure, the transient decay time (τ) increases, which indicates a decrease in photogenerated charge-carrier recombination. S-C3N4-dots also act as an optical antenna and increase the range of visible light absorbance of In2S3. The heterostructure can generate ∼2.38-fold higher photocurrent density of 1.18 V versus RHE in 3.5 wt % NaCl. The photoconversion efficiency of the heterostructure is 0.88% at 0.95 V versus RHE. The nanosheets of In2S3 and In2S3/S-C3N4-dots are stable, and photocurrent density is measured up to 2700 s under continuous back-illumination conditions.
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    Construction of CuS/Au Heterostructure through a Simple Photoreduction Route for Enhanced Electrochemical Hydrogen Evolution and Photocatalysis
    (Springer Nature, 2016-10-05) Pande, Surojit; Basu, Mrinmoyee; Nazir, Roshan
    An efficient Hydrogen evolution catalyst has been developed by decorating Au nanoparticle on the surface of CuS nanostructure following a green and environmental friendly approach. CuS nanostructure is synthesized through a simple wet-chemical route. CuS being a visible light photocatalyst is introduced to function as an efficient reducing agent. Photogenerated electron is used to reduce Au(III) on the surface of CuS to prepare CuS/Au heterostructure. The as-obtained heterostructure shows excellent performance in electrochemical H2 evolution reaction with promising durability in acidic condition, which could work as an efficient alternative for novel metals. The most efficient CuS-Au heterostructure can generate 10 mA/cm2 current density upon application of 0.179 V vs. RHE. CuS-Au heterostructure can also perform as an efficient photocatalyst for the degradation of organic pollutant. This dual nature of CuS and CuS/Au both in electrocatalysis and photocatalysis has been unveiled in this study.
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    Metal and Metal Oxide Nanostructure on Resin Support
    (Wiley, 2011-07-11) Basu, Mrinmoyee