Browsing by Author "Pande, Surojit"

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Ag2S/Ag Heterostructure: A Promising Electrocatalyst for the Hydrogen Evolution Reaction
(ACS, 2017) Basu, Mrinmoyee; Pande, Surojit; Gangopadhyay, Subhashis
Different metal chalcogenides, being a potential candidate for hydrogen evolution catalysts, have attracted enormous attention in the field of water splitting. In the present study, Ag2S/Ag is revealed as an efficient catalyst for hydrogen evolution. When a sacrificial template of the CuS nanostructure is used, Ag2S/Ag heterostructures are synthesized following a simple wet-chemical technique. Two different routes, wet chemical and hydrothermal, are followed to modulate the morphology of the CuS templates from flower ball to wirelike structures, which subsequently results in the formation of Ag2S nanostructure. Finally, the Ag layer is deposited on Ag2S with the help of a photoreduction technique. The unique heterostructure of Ag2S/Ag shows efficient catalytic activity in the H2 evolution reaction. A Ag2S/Ag wire can successfully generate a 10 mA/cm2 current density at a −0.199 V potential. Ag2S/Ag contains the micronanostructure where nanoplates of Ag2S/Ag assemble to give rise to microstructures such as flower balls and wire.
Aggregates of Ni/Ni(OH)2/NiOOH Nanoworms on Carbon Cloth for Electrocatalytic Hydrogen Evolution
(ACS, 2020-11-09) Basu, Mrinmoyee; Pande, Surojit
The development of an efficient electrocatalyst for hydrogen evolution reaction (HER) is essential to facilitate the practical application of water splitting. Here, we aim to develop an electrocatalyst, Ni/Ni(OH)2/NiOOH, via electrodeposition technique on carbon cloth, which shows efficient activity and durability for HER in an alkaline medium. Phase purity and morphology of the electrodeposited catalyst are determined using powder X-ray diffraction and electron microscopic techniques. The compositional and thermal stability of the catalyst is checked using X-ray photoelectron spectroscopy and thermogravimetry analysis. Electrodeposited Ni/Ni(OH)2/NiOOH material is an efficient, stable, and low-cost electrocatalyst for hydrogen evolution reaction in a 1.0 M KOH medium. The catalyst exhibits remarkable performance, achieving a current density of 10 mA/cm2 at a potential of −0.045 V vs reversible hydrogen electrode (RHE), and the Tafel slope value is 99.6 mV/dec. The overall electrocatalytic water splitting mechanism using Ni/Ni(OH)2/NiOOH catalyst is well explained, where formation and desorption of OH– ion on the catalyst surface are significant at alkaline pH. The developed electrocatalyst shows significant durability up to 200 h in a negative potential window in a highly corrosive alkaline environment along with efficient activity. The electrocatalyst can generate 165.6 μmol of H2 in ∼145 min of reaction time with 81.5% faradic efficiency.
Analysis of Poly(amidoamine) Dendrimer Structure by UV–Vis Spectroscopy
(ACS, 2011-06-29) Pande, Surojit
We report a UV–vis spectroscopic study of four different types of poly(amidoamine) dendrimers. The results indicate that the degree of protonation of the interior tertiary amines of these dendrimers correlates directly to an absorption band with λmax in the range of 280–285 nm. Specifically, at low pH, the tertiary amines are protonated and the 280–285 nm band is absent. However, at elevated pH, when these groups are deprotonated, this band appears. Similar results were obtained for a simple model compound. The dependence of the 280–285 nm band on the chemical state of the tertiary amines of the dendrimers was confirmed by complexing them with Pd2+ and Pt2+. In this case the band disappears, and it only reappears when the metal ions are decomplexed following reduction with BH4–. Finally, filtration experiments showed that the absorption band between 280−285 nm arises exclusively from intact, or nearly intact, dendrimers rather than low-molecular-weight fragments.
Bifunctional Tungsten-Doped Ni(OH)2/NiOOH Nanosheets for Overall Water Splitting in an Alkaline Medium
(ACS, 2022-02) Pande, Surojit
The development of a cost-effective and proficient bifunctional electrocatalyst is highly fascinating. Herein, we have synthesized a tungsten (W6+)-doped vertically grown nanosheet-like structure of Ni(OH)2/NiOOH on carbon cloth for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity in KOH solution. Doping with W6+ ions in Ni(OH)2/NiOOH is performed by electrodeposition, followed by the hydrothermal method. Various amounts of the dopant (W6+) are used to confirm the role of W, but the W0.1Ni(OH)2/NiOOH nanosheet shows the highest efficiency in electrocatalysis. The surface composition and the oxidation state of the developed electrocatalyst are confirmed by inductively coupled plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy analyses. After doping, the lattice suffers a tensile strain, which is confirmed by Raman and X-ray powder diffraction analyses. Field emission scanning electron microscopy and transmission electron microscopy analyses confirm the nanosheet morphology of W0.1Ni(OH)2/NiOOH. The electrocatalyst, W0.1Ni(OH)2/NiOOH, has a lower value of overpotential of 56 and 293 mV to obtain current densities of 10 and 50 mA/cm2 for HER and OER, respectively, in a basic medium. The corresponding Tafel slope values are 63.5 and 48.2 mV dec–1 for HER and OER, respectively. In W0.1Ni(OH)2/NiOOH, the W6+ ion is a d0 system that behaves as a strong Lewis acid and helps in electron pulling from Ni2+ ions, which facilitates the formation of Ni3+ ions as an active site for HER and OER. The electron pulling nature of the W6+ ion is further confirmed from Bader’s charge analysis. Moreover, the synergistic effect between Ni2+ and W6+ ions plays an important role in a higher electrocatalytic efficiency. Density functional theory calculations revealed an increase in the Gibbs free energy of H adsorption in the presence of W, suggesting an enhanced HER activity for W0.1Ni(OH)2/NiOOH.
Ce-doped nise nanosheets on carbon cloth for electrochemical water-splitting
(ACS, 2024-04) Pande, Surojit
Developing an affordable and efficient electrocatalyst for bifunctional activity is crucial for the advancement of water electrolysis technology. Doping with foreign atoms in electrocatalysts can tune the electronic properties, which further improves the water-splitting process. Herein, we have developed Ce-doped Ni0.85Se as a bifunctional electrocatalyst in an alkaline medium. The hydrothermal method was used to develop a two-dimensional (2D) nanosheet of the Ce-doped Ni0.85Se electrocatalyst. The as-developed pristine and doped electrocatalysts were characterized through various techniques. The optimized Ce0.1Ni0.85Se electrocatalyst represents −0.238 and 1.56 V vs reversible hydrogen electrode as an onset potential for hydrogen and oxygen evolution reactions, respectively, to generate 20 and 50 mA/cm2 current density. The Ce0.1Ni0.85Se electrocatalyst works as a suitable cell in an alkaline medium with 1.73 V to generate 10 mA/cm2 and 24 h stability. The introduction of Ce doping plays a pivotal role in tuning the electronic environment and facilitating a synergistic effect, ultimately improving the overall efficiency. Moreover, the active sites for water splitting were generated by expansion and distortion in the Ni0.85Se lattice. The enhanced specific surface area and porous 2D nanosheets of the doped sample are beneficial for water splitting. The theoretical results also prove that after doping with Ce, the catalyst has zero band gap, optimum Gibbs hydrogen adsorption energy, and an electronic state are the reasons for improved electrocatalytic performance. The actual active sites in the Ce-doped Ni0.85Se electrocatalyst were determined with density functional theory calculations. Therefore, this idea can generate a route for developing a doped electrocatalyst with efficient and stable activity.
Co-Doped Ni9S8 Nanostructures for Electrocatalytic Water Splitting over a Wide pH Range
(ACS, 2022-07) Pande, Surojit
As a replacement for renewable energy sources, an earth-abundant electrocatalyst for water splitting is effectively explored. In this work, Ni9S8 and cobalt-doped Ni9S8 nanostructures are fabricated on carbon cloth using the hydrothermal technique. The developed electrocatalysts are characterized through various techniques, for example, powder X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy , the Brunauer–Emmett–Teller method, and inductively coupled plasma atomic emission spectroscopy. Tuning of cobalt doping is performed to obtain the best optimized ratio of Co/Ni for electrocatalytic activity. All the developed materials are used for a water splitting reaction in an alkaline electrolyzer, and Co0.05Ni8.95S8 is an optimized material for both hydrogen and oxygen evolution. The electrocatalyst Co0.05Ni8.95S8 only requires −0.151 V versus RHE (reversible hydrogen electrode) to obtain a 10 mA/cm2 current density in the hydrogen evolution reaction (HER), and in the oxygen evolution reaction (OER), it requires 1.557 V versus RHE to generate a 30 mA/cm2 current density. The corresponding Tafel slope values for the HER and OER are 125 and 49.8 mV/dec, respectively, obtained by using Co0.05Ni8.95S8 electrocatalysts in 1.0 M KOH solution. The stability of Co0.05Ni8.95S8 is also checked, and it is stable for up to 60 and 80 h for the HER and OER, respectively. The cell voltage of 1.89 V is required to generate a 10 mA/cm2 current density for the overall water splitting reaction. The electrocatalyst is also used for the HER and OER in a wide pH range for practical applicability. The overall experimental findings were verified by theoretical calculations, which state that the higher metallic nature of Co-doped Ni9S8 facilitates efficient electrocatalytic activity. The optimum Gibbs free energy and hydrogen and oxygen coverage calculations also prove that the optimized Co0.05Ni8.95S8 electrocatalyst exhibits the best HER and OER activity. Therefore, this work provides a robust electrocatalyst for the electrocatalytic water splitting reaction.
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.
Construction of CuS/Au Heterostructure through a Simple Photoreduction Route for Enhanced Electrochemical Hydrogen Evolution and Photocatalysis
(Nature, 2016-10) Basu, Mrinmoyee; Pande, Surojit
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
Decoration of Carbon Nitride Surface with Bimetallic Nanoparticles (Ag/Pt, Ag/Pd, and Ag/Au) via Galvanic Exchange for Hydrogen Evolution Reaction
(ACS, 2017) Basu, Mrinmoyee; Pande, Surojit
Here, we propose the synthesis of AgPt, AgPd, and AgAu bimetallic nanoparticles (NPs) on a carbon nitride (C3N4) surface via a galvanic exchange technique for the hydrogen evolution reaction (HER). Prior to the synthesis of C3N4/AgPt, AgPd, and AgAu, Ag NPs were synthesized on a C3N4 surface. For the synthesis of Ag NPs, initially Ag+ ions were adsorbed and then reduced by NaBH4 resulting in the decoration of Ag NPs. These Ag NPs were then subjected to galvanic exchange where sacrificial Ag was replaced by Pt2+, Pd2+, and Au3+ to fabricate AgPt, AgPd, and AgAu NPs. The galvanic exchange reaction occurs on a solid substrate, which favored slow exchange of Ag and resulted in the transformation of Ag into AgPt, AgPd, and AgAu alloys. The synthesized heterostructures were characterized with the help of PXRD, XPS, TEM, FESEM, and EDS techniques. All the materials were applied for hydrogen evolution using 0.5 M H2SO4 solution. C3N4/AgPt shows efficient electrocatalytic activity as it requires only −150 mV potential to attain current density of 10 mA/cm2. Bimetallic catalysts synthesized through galvanic exchange proved very efficient as compared to monometallic C3N4/Ag.
Decoration of Carbon Nitride Surface with Bimetallic Nanoparticles (Ag/Pt, Ag/Pd, and Ag/Au) via Galvanic Exchange for Hydrogen Evolution Reaction
(ACS, 2017-08-21) Pande, Surojit
Here, we propose the synthesis of AgPt, AgPd, and AgAu bimetallic nanoparticles (NPs) on a carbon nitride (C3N4) surface via a galvanic exchange technique for the hydrogen evolution reaction (HER). Prior to the synthesis of C3N4/AgPt, AgPd, and AgAu, Ag NPs were synthesized on a C3N4 surface. For the synthesis of Ag NPs, initially Ag+ ions were adsorbed and then reduced by NaBH4 resulting in the decoration of Ag NPs. These Ag NPs were then subjected to galvanic exchange where sacrificial Ag was replaced by Pt2+, Pd2+, and Au3+ to fabricate AgPt, AgPd, and AgAu NPs. The galvanic exchange reaction occurs on a solid substrate, which favored slow exchange of Ag and resulted in the transformation of Ag into AgPt, AgPd, and AgAu alloys. The synthesized heterostructures were characterized with the help of PXRD, XPS, TEM, FESEM, and EDS techniques. All the materials were applied for hydrogen evolution using 0.5 M H2SO4 solution. C3N4/AgPt shows efficient electrocatalytic activity as it requires only −150 mV potential to attain current density of 10 mA/cm2. Bimetallic catalysts synthesized through galvanic exchange proved very efficient as compared to monometallic C3N4/Ag.
Decoration of Carbon Nitride Surface with Bimetallic Nanoparticles (Ag/Pt, Ag/Pd, and Ag/Au) via Galvanic Exchange for Hydrogen Evolution Reaction
(ACS, 2017-08-21) Basu, Mrinmoyee; Pande, Surojit
Here, we propose the synthesis of AgPt, AgPd, and AgAu bimetallic nanoparticles (NPs) on a carbon nitride (C3N4) surface via a galvanic exchange technique for the hydrogen evolution reaction (HER). Prior to the synthesis of C3N4/AgPt, AgPd, and AgAu, Ag NPs were synthesized on a C3N4 surface. For the synthesis of Ag NPs, initially Ag+ ions were adsorbed and then reduced by NaBH4 resulting in the decoration of Ag NPs. These Ag NPs were then subjected to galvanic exchange where sacrificial Ag was replaced by Pt2+, Pd2+, and Au3+ to fabricate AgPt, AgPd, and AgAu NPs. The galvanic exchange reaction occurs on a solid substrate, which favored slow exchange of Ag and resulted in the transformation of Ag into AgPt, AgPd, and AgAu alloys. The synthesized heterostructures were characterized with the help of PXRD, XPS, TEM, FESEM, and EDS techniques. All the materials were applied for hydrogen evolution using 0.5 M H2SO4 solution. C3N4/AgPt shows efficient electrocatalytic activity as it requires only −150 mV potential to attain current density of 10 mA/cm2. Bimetallic catalysts synthesized through galvanic exchange proved very efficient as compared to monometallic C3N4/Ag.
Decoration of MoS2 on g-C3N4 surface for efficient hydrogen evolution reaction
(Elsiever, 2017-12-20) Pande, Surojit
The increasing demand for energy and strain on the environment due to human activities has led to an increased focus on the development of cleaner alternative fuels. Hydrogen gas is found as a substitute in the progress of sustainable energy sources due to its high calorific values and clean combustion products. In this work molybdenum disulfide (MoS2) decorated on graphitic carbon nitride (g-C3N4) was synthesized via a simple hydrothermal route. The morphology and surface structure of MoS2/g-C3N4 were analyzed by SEM, TEM, and EDS techniques. The crystal structure, optical properties, and elemental composition of the catalyst were investigated by PXRD, UV–vis, RAMAN, and XPS. BET analysis is carried out to determine the surface area of both MoS2 and MoS2/g-C3N4. The catalyst material, MoS2/g-C3N4 demonstrates enormous improvement in production of H2 with low onset potentials (−0.24 V vs. RHE), small Tafel slop (63 mV/dec), and excellent cycling stability as compared with bare MoS2. The enhanced electrochemical performance of the MoS2/g-C3N4 heterostructure could be attributed to higher charge carrier mobility in heterostructure interface, improved specific activity and large surface area. The focus of this study is to construct a new MoS2 based semiconductor heterostructure electrocatalyst with improved HER activity.
Decoration of Pd and Pt nanoparticles on a carbon nitride (C3N4) surface for nitro-compounds reduction and hydrogen evolution reaction
(RSC, 2017) Basu, Mrinmoyee; Gangopadhyay, Subhashis; Pande, Surojit
Herein, we propose the synthesis of Pd and Pt monometallic nanoparticles on a carbon nitride (C3N4) surface for the reduction of nitro compounds as well as for electrocatalysis. For the synthesis of C3N4/Pd and C3N4/Pt, metal ions were initially adsorbed on the C3N4 surface and then subsequently reduced by NaBH4. The as-synthesized heterostructures were authenticated by different characterization techniques: UV-vis, PXRD, XPS, TEM, FESEM, and EDS. Decorations of monometallic NPs on C3N4 not only improved the reduction efficiency of nitro-compounds but also enhanced the electrocatalytic activity in the hydrogen evolution reaction. C3N4/Pt proved to be an efficient electrocatalyst as it requires a potential of −0.339 V to attain a current density of 10 mA cm−2; whereas, C3N4/Pd requires −0.371 V to reach a current density of 10 mA cm−2vs. Ag/AgCl. Both C3N4/Pd and Pt heterostructures are better than bare C3N4, which needs −0.596 V to achieve a current density of 10 mA cm−2vs. Ag/AgCl. On the other hand, C3N4/Pd showed a better performance in nitro-compound reduction compared to C3N4/Pt and bare C3N4. The kinetic study reveals that the rate constant using a C3N4/Pd catalyst is 6.7 × 10−1 min−1 for p-nitroaniline reduction, which is 101 times higher compared to bare C3N4 and 4.7 times higher in comparison to C3N4/Pt.
Dendrimer-encapsulated nanoparticles: New synthetic and characterization methods and catalytic applications
(RSC, 2011) Pande, Surojit
In this article we describe the synthesis, characterization, and applications of dendrimer-encapsulated nanoparticles (DENs). These materials are synthesized using a template approach in which metal ions are extracted into the interior of dendrimers and then subsequently reduced chemically to yield nearly size-monodisperse particles having diameters in the 1–2 nm range. Monometallic, bimetallic (alloy and core@shell), and semiconductor nanoparticles have been prepared by this route. The dendrimer component of these composites serves not only as a template for preparing the nanoparticle replica, but also as a stabilizer for the nanoparticle. In this perspective, we report on progress in the synthesis, characterization, and applications of these materials since our last review in 2005. Significant advances in the synthesis of core@shell DENs, characterization, and applications to homogeneous and heterogeneous catalysis (including electrocatalysis) are emphasized.
Development of Copper Cobalt Sulfide with Cu : Co Ratio Variation on Carbon Cloth as an Efficient Electrode Material for the Oxygen Evolution Reaction
(Wiley, 2019-10) Pande, Surojit
When designing a device for energy conversion, development of a highly active catalyst for OER (oxygen evolution reaction) reaction in alkaline medium is of utmost importance. For energy conversion, herein, we developed copper cobalt sulfide on carbon cloth (CC) using a simple and facile hydrothermal method. A vertically grown 2D sheet-like structure of copper-cobalt sulfide is observed using L-cysteine as a sulfur source. An optimized ratio of copper(II) and cobalt(III) and the best sulfur source are found to boost the electrocatalytic activity of mixed metal thiospinel for OER. Several characterization techniques (XRD, Raman, FESEM, TEM, XPS, and ICP-AES) were used to confirm phase purity, morphology, and composition of copper cobalt sulfides. We have established that 2D nanosheets of CuCo3Sz/CC exhibited superior electrocatalytic performance over bare RuO2 in 1.0 M KOH solution. It is observed that CuCo3Sz/CC need only 105 mV overpotential to generate 5 mA/cm2 current density. CuCo3Sz/CC is very stable and able to produce unaltered current density under an applied potential of 1.615 V vs. RHE for 48 h. Electrochemically active surface area calculation is performed for all catalysts to confirm higher electrocatalytic activity. The catalyst, CuCo3Sz/CC is used in a broad pH region using 0.5 M KOH, saline water, and 0.5 M Na2SO4 electrolyte solution to widen the applicability of water splitting. This work shows an avenue to develop active and durable electrocatalyst for OER without using any noble metal electrocatalyst.
Dopamine Molecules on Aucore−Agshell Bimetallic Nanocolloids: Fourier Transform Infrared, Raman, and Surface-Enhanced Raman Spectroscopy Study Aided by Density Functional Theory
(ACS, 2009) Pande, Surojit
Adsorption of dopamine (DA) on a Aucore−Agshell bimetallic nanocolloidal surface has been investigated using surface-enhanced Raman spectroscopy (SERS). The normal Raman spectra (NRS) of DA molecules in bulk and in aqueous solution have been investigated in depth. The vibrational signatures, as observed from the Raman and FTIR spectra of the molecule, have been assigned from the potential energy distributions. The pH-dependent NRS of the DA molecule in aqueous solution has been recorded to elucidate the protonation effect and preferential existence of different forms of the molecule. The pH-dependent SERS spectra of the molecule adsorbed on the bimetallic Aucore−Agshell nanocolloidal surface are also reported. The enhancement of bands in the pH-dependent SERS spectra suggests that the molecules are adsorbed onto the bimetallic Aucore−Agshell surface with the molecular plane tilted with respect to the silver surface of Aucore−Agshell bimetallic nanoparticles. The model study authenticates the spectral disposition and orientation of the molecule. Thus, experiment and theory keep abreast of the variety of DA structures envisaged from SERS studies on a new substrate.
Doped nickel-based nanocatalysts for electrochemical water splitting: a review
(ACS, 2025-10) Pande, Surojit
The growing demand for clean energy solutions to address fossil fuel depletion and global warming has increased the pace for the search for sustainable alternatives. To address this situation, hydrogen energy is emerging as a promising method due to its zero pollution and high energy density. Electrocatalytic water splitting is a promising technology for large-scale hydrogen production. Generally, electrocatalysts work well for either the HER or the OER, but not both. Developing catalysts that can be efficiently used for overall water splitting is necessary for commercial viability. Nickel-based materials, specifically when doped with metals (e.g., Fe, Co, W, Cu, Ru, and Ir) and nonmetals (e.g., C, F, and P), have shown great potential because of their versatile chemical properties, corrosion resistance, and structural stability. This review provides a comprehensive overview of recent advancements in doped nickel-based electrocatalysts, which focuses on nickel oxides, chalcogenides, phosphides, nitrides, and single-atom catalysts (SACs). It discusses fundamental mechanisms of HER and OER, strategies for enhancing electrocatalytic performance through doping, defect engineering, and electronic structure modulation. It also discusses the effect of nonmetal and metal doping on activity and stability. The review also emphasizes the importance of systematic experimental approaches like doping ratios, accurate surface area corrections, and operando methods to better understand the relationship between electronic structure and electrocatalytic performance. It also highlights the research gaps and the future directions that aim to advance the design of efficient, stable, and cost-effective nickel-based electrocatalysts, which can contribute to the development of sustainable hydrogen energy production.
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.
Effect of Substrates on the Photoelectrochemical Reduction of Water over Cathodically Electrodeposited p-Type Cu2O Thin Films
(ACS, 2015-08-05) Pande, Surojit
In this study, we demonstrate development of p-Cu2O thin films through cathodic electrodeposition technique at constant current of 0.1 mA/cm2 on Cu, Al, and indium tin oxide (ITO) substrates from basic CuSO4 solution containing Triton X-100 as the surfactant at 30–35 °C. The optical and morphological characterizations of the semiconductors have been carried out using UV–vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The band gap energy of ∼2.1 eV is recorded, whereas SEM reveals that the surface morphology is covered with Cu2O semiconductors. XRD analyses confirm that with change in substrate, the size of Cu2O “cubic” crystallites decreases from ITO to Al to Cu substrates. Photoelectrochemical characterizations under dark and illuminated conditions have been carried out through linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopic analysis. The photoelectrochemical reduction of water (H2O → H2) in pH 4.9 aqueous solutions over the different substrates vary in the order of Cu > Al > ITO. The highest current of 4.6 mA/cm2 has been recorded over the Cu substrate even at a low illumination of 35 mW/cm2, which is significantly higher than the values (2.4 mA/cm2 on Au coated FTO or 4.07 mA/cm2 on Cu foil substrate at an illumination of 100 mW/cm2) reported in literature.
Fabrication of Au decorated MoS2 Langmuir Blodgett film as SERS sensing scaffold for detection of thiram in aqueous solution and in carrot peels
(Elsevier, 2024-10) Pande, Surojit
This paper is focused on simple fabrication of robust and reproducible SERS active substrate through self-assembly of gold nanoparticles (AuNps) entrapped in the Langmuir Blodgett (LB) film of MoS2 flakes. The as prepared Au-MoS2 substrate can detect SERS signals of 4-Mercapto Pyridine (4-Mpy) molecules at trace concentrations down to 10-12 M. The substrate has been further employed in detecting thiram (TH) both in aqueous solution and in carrot peels (CPls). The limit of detection (LOD) of TH in aqueous medium and in CPls have been estimated to be ∼ 5.18 and 10.16 pM respectively. We believe that the applicability of this SERS active substrate may be extended in the trace detections of explosives, drugs and in diagnostic applications.