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Reduced graphene oxide (RGO)-supported Pd–CeO2 nanoparticles prepared by a chemical reduction method were shown to exhibit superior electrocatalytic activity towards formic acid compared to the commercial Pd/C catalyst.

The green energy alternative to a fossil fuel-based economy can be provided only by coupling renewable energy solution solutions such as solar or wind energy plants with large-scale electrochemical energy storage devices. Enabling high-energy storage coupled with high-power delivery can be envisaged though high-capacitive pseudocapacitor electrodes. A pseudocapacitor electrode with multiple oxidation state accessibility can enable more than 1e- charge/transfer per molecule to facilitate superior energy storage. K-doped LaFeO3 (La1-x K x FeO3-δ) is presented here as an electrode having a high pseudocapacitance storage, equivalent to 1.32e- charge/transfer per molecule, resulting in a capacity equivalent of 662 F/g at 1 mV/s scan rate by introduction of a layered potential over the Fe-ion octahedral to utilize higher redox state energies (Fe4+→ Fe2+). La/K ordering in orthorhombic perovskite (La1-x K x FeO3-δ) made the Fe4+ oxidation state accessible, and a systematic shift in the redox energies of Fe4+/3+ and Fe3+/2+ redox couples was observed with K+ ion doping in the A site of the LaFeO3 perovskite, which resulted in a high faradic contribution to the capacitance, coupled with anionic intercalation of H2O/OH- in the host perovskite lattice. The surface capacitive and diffusion control contributions for capacitance are about 42 and 58%, respectively, at -0.6 V, with a scan rate of 1 mV/s. A high gravimetric capacitance, equivalent to 619, 347, 188, 121, and 65 F/g, respectively, at 1, 2, 3, 5, and 10 A/g constant current, was observed for the La0.5K0.5FeO3-δ electrode. Up to 88.9% capacitive retention and 97% Coulombic efficacy were obtained for continuous 5000 cycles of charge/discharge for the La0.5K0.5FeO3-δ electrode. The gravimetric capacitance values of ASCs (activated carbon//La0.5K0.5FeO3-δ) are 348, 290, 228, and 147 F/g at current densities of 1, 2, 3, and 5 A/g, respectively. A maximum specific power of ∼3594 W/kg was obtained when the specific energy reached ∼117 Wh/kg at 5 A/g of current density.

The sustainable production of hydrogen and oxygen through the electrolysis of water requires the development of an efficient electrocatalyst. In this work, we report the electrocatalytic activity of Pd nanoparticles dispersed on CeO2/N, S-rGO (where N, S-rGO represents nitrogen and sulfur-doped reduced graphene oxide). The CeO2/N, S-rGO and Pd nanoparticles were synthesized by hydrothermal and chemical reduction methods, respectively. Electrochemical measurements towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) show a high electrocatalytic activity of the catalyst. Among the synthesized electrocatalysts Pd/CeO2/N, S-rGO exhibits lower overpotential (75 mV and 240 mV) at 10 mA/cm2 and lower Tafel slope value (44 mV/dec and 42 mV/dec) for HER and OER, respectively. The chronoamperometric and linear sweep voltammetry (LSV) of the electrocatalyst shows a negligible decrease in the current density for twelve hours and a minor change in the polarization curve after 10,000 cycles, respectively. The high electrocatalytic activity and superior stability of the synthesized electrocatalyst could be attributed to the synergetic effect between Pd nanoparticles and CeO2/N, S-rGO support. This work demonstrates a facile way to develop effective and stable electrocatalysts by exploiting the Pd/Metal oxide interface.

Palladium and palladium-silver alloy nano catalysts were synthesized from aqueous precursor at room temperature via a single vessel chemical reduction and co-reduction methods in absence of capping agent. XPS analysis confirms the presence of Pd and Ag in the catalyst matrix. Microscopic analyses reveal spherical morphology of the catalyst in the nanoscale dimension. The electro-analytical investigation of the catalyst loaded on carbon electrode shows that the Pd4Ag nano alloy catalyst demonstrates marked improvement in electro-catalytic efficiency among all prepared catalysts for ethanol oxidation in alkali. The Pd4Ag/C catalyst shows the mass normalized peak current density of 522 mA mg−1Pd in cyclic voltammetric (CV) study, which is 1.97 times greater than that of similarly synthesized Pd/C (264.2 mA mg−1Pd) catalyst. Chronoamperometric and impedance analyses further establish the superiority of Pd4Ag/C catalyst. To discover the plausible mechanism, the CV study is typically extended to the intermediates like sodium acetate which reveals that though Pd is better for catalytic oxidation of intermediate than the best catalyst but the optimal OH− adsorption on the surface of the metal, favours catalytic oxidation of ethanol more on Pd4Ag catalyst. The mechanistic path of the reaction is anticipated by evaluating the ex-situ FTIR and chromatographic studies which explain the promotion of the formation of carboxylate in comparison to carbonate by Ag.

Developing a fuel cell model with fundamental structural properties such as distribution of pore size, geometrical network of individual phase, and volume-specific interfacial area are critical in evaluating the accurate cell performance. Therefore, herein, by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) tomography, three-dimensional (3-D) microstructure of CLs is reconstructed from two real-time samples: (i) High tortuosity humidifying catalyst layer (HTH CL) and (ii) standard catalyst layer. From the reconstructed microstructure, water imbibition behavior at different levels of capillary pressure is simulated and the effective transport properties such as gas permeability, gas diffusivity, surface area and water permeability are derived as well. By coupling the effective structural and transport properties, a 2D model is developed to predict the performances of the two CLs, at relative humidity (RH) levels of 20% and 100%. Since the effective transport properties are derived from real-time samples, this 2D model is expected to have a greater accuracy in predicting the fuel cell performance. Finally, the mechanism of self-humidifying MEA at lower and higher RH conditions (20% RH and 100% RH) is demonstrated as a function of liquid water saturation in the cathode CL and water dry-out in the anode CL.

Designing an efficient and stable electrocatalyst made of earth abundant elements to take over expensive noble metal based for Hydrogen Evolution Reaction (HER) have been focused. Cobalt disulfide-molybdenum disulfide nanocomposite supported by nitrogen doped reduced graphene oxide and multiwalled carbon nanotubes (CoS2/MoS2@NrGO-MWCNT) is reported as an efficient electrocatalyst for HER. CoS2/MoS2@N-rGO-MWCNT and ternary hybrids composed of CoS2, MoS2 and N-rGO/MWCNT have been investigated. The catalysts were prepared by facile hydrothermal method, and the optimal doping ratio referred to date cobalt to molybdenum as 2:1 was chosen. It is found that co-existence of CoS2, MoS2 brings abundant active sites and incorporation of MWCNT offered stability. Good dispersion of CoS2 nanoparticles on graphene and MoS2 sheets is observed. Additionally nitrogen doping on rGO sheets has been carried out to boost up the electronegativity of the catalyst as a support to enhance the catalytic activity of CoS2/MoS2 for refine structure and better electrical conductance. Precisely, CoS2/MoS2@N-rGO-MWCNT exhibited smaller tafel slope 73 mV dec−1 at overpotential 281 mV for current density 10 mA cm−2 and the substantial stability of 14 h is recorded in 0.5 M H2SO4 medium, results suggest that catalyst is viable alternate for HER.

The electrochemical behavior of V2O5 spindle-like nanostructures synthesized through hydrothermal method is studied for supercapacitor applications. The electrochemical supercapacitive performance of the prepared electrode was investigated using cyclic voltammeters (CV), Chronopotentiometry (CP), and Electrochemical impedance spectroscopy (EIS) analyses. The crystallographic structure and phase purity of the V2O5 electrode is investigated by the X-ray diffraction (XRD) analysis. To further confirm the formation of V2O5, the Fourier-transform infrared (FT-IR) spectroscopy, and Fourier-transform Raman spectroscopy (FT-Raman) investigations were carried out. The formation of V2O5 is confirmed by high-resolution transmission electron microscopy (HR-TEM) analyses. The electrode material delivered a high specific capacitance of 403F/g at 1A/g current density in the mixed electrolyte solution (1 M Na2SO4 + 0.5 M KOH). In this mixed electrolyte, V2O5 spindle-like electrode showed a good cyclic stability of 3000 cycles with better capacity retention of 85% at 10A/g.

In this report, ternary Al–Mg–Ag alloy is introduced as novel support material as well as active promoter for palladium nano catalyst. The catalytic activity is explored with respect to ethanol oxidation reaction (EOR) in alkali. Pd nanoparticles supported on Al–Mg–Ag alloy is synthesized using a facile rapid solidification of melt method followed by chemical reduction. X-ray diffraction and microscopic analysis revealed uniformly distributed spherical Pd particle of nano dimension is formed on the support material. The application of the prepared catalysts for electro-chemical oxidation of ethanol is assessed by cyclic voltammetry (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) study. Pd/Al–Mg–Ag catalyst show remarkably high peak current density (1971 mA mg−1Pd) for EOR which is 3.36 times higher than commercial Pd/C (20%) catalyst. In addition, the synthesized catalyst show low onset potential and excellent stability towards long-term application as anode catalyst for fuel cells. The study portrays Al–Mg–Ag trimetallic alloy as a promising support material and an effective promoter. The boosted catalytic activity may be attributed to the high dispersion, high Pd utilization, synergy between metals and superior conduction between support material and Pd nanoparticles.

Microbial fuel cells, an emerging technology has been paid a great attention in recent years, due to its unique advantages in treating wastewater to portable water, together with the generation of useful electricity, with the help of bio-active anodes and electrochemical cathodes, simultaneously. When applying this technology in a practical scale, the indigenous bacteria present in the wastewater catalyze the breakdown of organic matter in the anode compartment, with generation of electrons and in the cathode compartment an oxidant, usually the oxygen present in the air, take the electron and reduce to water (oxygen reduction reaction, ORR). An ideal ORR catalyst should be highly active, durable, scalable, and most importantly it should be cost effective. Generally, platinum-based catalyst is utilized, however, due to the high cost of Pt based catalysts, many cheap, cost effective catalyst have been identified as efficient ORR catalyst. Carbon based catalysts known to possess good electronic conductivity, desirable surface area, high stability, together when doped with heteroatoms and cheap metals is found to remarkably enhance the ORR activity. Although a lot of research has been done in view of developing carbon based cheap, cost-effective catalysts, still their collective information has not been reviewed. In this article we anticipate reviewing various non-precious metal and metal-free catalysts that are synthesized and investigated for MFCs, factors that affect the ORR activity, catalyst designing strategies, membranes utilized for MFCs, together with the cost comparison of non-precious and metal-free catalysts with respect to Pt based catalysts have been summarized. We anticipate that this review could offer researchers an overview of the catalyst developed so far in the literatures and provides a direction to the young researchers.

Highly durable and active CeO2 on biochar carbon (CeO2/BC) derived from Spirulina platensis microalgae and synthesized by simple one-pot hydrothermal treatment and further activated through pyrolysis approach. A spindle-shaped morphology of CeO2 with predominant (111) facet was evidently observed from X-ray diffraction patterns and electron microscopy images. The structural features such as high specific surface area, defect-rich carbon with N & P atoms, increased oxygen vacancy and π-electron transfer play an important role for the improved oxygen reduction reaction (ORR). The considerable amount of Ce3+ and higher proportion of pyridinic N and graphitic N species are substantially contributed to the superior ORR performance of CeO2/BC700, which surpasses other similar catalysts and competing with Pt/C. Hence, the significant kinetic ORR parameters and extended stability (no loss after 5000 potential cycles) of the CeO2/BC700 catalysts provides the promising insight to develop the rare-earth metal oxide nanostructures as a possible candidate for ORR in alkaline medium.

Transition metal chalcogenides have garnered wide attention of the researchers in energy storage and conversion domains owing to their superior electronic conductivity, mechanical and thermal constancy. Zinc Sulfide (ZnS) has been identified as one of the most important II–VI semiconductor, with a band gap of 3.5–3.8 eV. Excellent ion accessibility and charge storage ability of nanosized ZnS makes this a prospective material in the field of energy storage. Besides ZnS nanoparticle possess advantages such as good electric conductivity, low diffusion resistance, fast electron transportation, non-toxic nature etc. It is a lightweight and cost effective material compared to other metal sulfides. Reports are available on supercapacitor electrodes based on different types of ZnS nanocomposites. However, investigation on the variation of this material’s energy storage efficiency with metal doping and increased particle size are comparatively less. ZnS particles with microsphere morphology show enhanced reversibility due to less self-aggregation and volume expansion. In this work we report the synthesis and electrochemical studies of pure & nickel (Ni) doped ZnS microspheres. The synthesis of pure and Ni doped ZnS microspheres were carried out by hydrothermal method. The crystal structure, phase composition, and microstructure of the samples were analyzed by X-ray diffractometer (XRD) and Field Emission Scanning Electron Microscope (FESEM) respectively. The electrochemical behavior of pure ZnS and Ni doped ZnS microspheres were examined by means of Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, and Galvanostatic charge–discharge. At 5A g−1 current density, Ni doped ZnS microspheres exhibited an enhanced specific capacitance of 104.2 F g−1 where pure ZnS microspheres showed 67.75F g−1.

The Bismuth based Zinc metal oxide (ZnBi12O20) nanorods were synthesized via single step solvothermal approach. The characterization of synthesized hybridized structure was done by several analysis such as X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UVvis–DRS), Fourier transform-infrared spectroscopy (FT–IR), Thermogravimetric analysis (TGA), Raman spectroscopy, Field-Emission scanning electron microscopy (FESEM), Energy dispersive analysis of X-rays (EDX), High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy. The photocatalytic activity of ZnBi12O20 and an incorporation of varying weight percentages of GO (1–4 wt %) into ZnBi12O20 catalyst (GZBC) were analyzed under visible light irradiation by the degradation of an aqueous solution of Methylene blue (MB) and Methyl orange (MO) dye. Among various developed nanocomposites, 3 wt% GZBC reduced graphene oxide exfoliated nanocomposites has revealed the degradation efficiency as 96.04, 94.52% at 100 and 120 min for MB and MO respectively with enriched visible light absorption range. The photocatalytic property of 3 wt % reduced graphene oxide exhibits higher degradation behavior than that of other synthesized nano-composites.

Herein, the relationship between oxygen reduction reaction (ORR) catalytic activities of N-doped hollow graphene spheres (N-HGSs) and their morphologies, microstructures, and nitrogen doping configuration is deeply investigated. Based on all detection results it can be concluded that all of the level and configuration of doped-N atoms, the surface area, the mesopore structure of fabricated hollow graphene spheres related to the exposure of edges and vacancies correlating with the active sites, will ultimately affect the ORR catalytic performance of N-HGSs. Therefore, the optimized synthesis of N-HGSs can produce efficient electrocatalyst for ORR, which is better than the noble-metal Pt/C catalysts and most highly active graphene-based ORR catalysts reported to date. Additionally, the optimized synthesis of N-HGSs also exhibit excellent performance in sodium-ion storage. Because the large specific surface area, the well-connected hollow spherical and mesopore structures and the increased hydrophilicity induced by the doped-N atoms facilitate a ready transfer of charges and adsorption, diffusion and desorption of Na+ ions in and out of the active material, which could enhance sodium ion storage capacity. Additionally, expect the storage of Na+ ions by surface electro-adsorption/desorption, the insertion/extraction of Na+ through the thinner graphene shell makes a significant contribution to the improvement of sodium-ion storage capacity.

In this present study, semiconductor magnetic α-Fe2O3/MnO2 nanocomposites (NCs) were prepared by a facile hydrothermal (HT) method. The crystallographic structure, morphology, chemical configuration and magnetic features were analysed by X-ray powder diffraction (XRD), high resolution scanning electron microscope (HR-SEM), energy dispersive X-ray analysis (EDX), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) analyses. The as-prepared NCs were used as an electrode in energy storing supercapacitor was systematically examined. The electrochemical deeds of α-Fe2O3/MnO2 NCs was analysed by cyclic voltammetry (C–V) and galvanostatic charge–discharge (GCD) tests. The CV analysis of the NCs electrode showed a distinctive pseudocapacitive behaviour in 1 M KOH solution. The NCs electrode reveals enhanced specific capacitance compared to plain α-Fe2O3 and MnO2 nanoparticles (NPs) and generates high specific capacitance of 216.35 Fg−1. Pseudocapacitor obtains of energy density 135.42 Wh kg−1 at power density of 6.399 kW kg−1, indicating the as-prepared α-Fe2O3/MnO2 NCs shows noteworthy high-energy, specific capacitance, power densities and long-standing cyclic stability with 89.2% of preliminary capacitance reserved at 1A g−1 after 10000 cycles in judgement with the pure α-Fe2O3 and MnO2 NPs electrode. The α-Fe2O3/MnO2 NCs electrode having noteworthy electrochemical characteristics performance renders promising applications in energy storing systems.

Accumulation of excess water in Proton exchange membrane fuel cell (PEMFC) is one of the significant technical challenges that needs great attention, since it makes the performance of the fuel cell highly unpredictable and unreliable. To address this formidable task, herein by inserting porous inserts in inline and staggered arrangements on the provisions of landing surface of serpentine flow field, we minimize water clogging in gas diffusion layer. Two types of porous inserts namely porous carbon inserts (PCI), porous sponge inserts (PSI) of sizes 2 mm × 2 mm x 2 mm (2 mm porous inserts) and 4 mm × 2 mm x 2 mm (4 mm porous inserts) are tested for water management of PEMFC, and their respective performances are analyzed. The results showed that power density produced by MSI flow field is 9.5% and 11.57% higher than serpentine flow field for 2 mm and 4 mm PCI respectively while the MSS flow field produced 31.81% and 42.56% higher performance in terms of power density compared with serpentine flow field for 2 mm and 4 mm PCI respectively. The MSS flow field with 4 mm PCI produced 27.77% higher power density compared with 2 mm PCI. Using porous sponge insert instead of porous carbon insert increases the power density by 23.33% for 2 mm porous insert and the power density increases 21.73% for 4 mm PSI in MSS flow field. Increasing the size of PSI from 2 mm to 4 mm increases the power density by 26.12% in MSS flow field.

Commercial viability of fuel cells is limited as it does not produce the same power density while scaling and stacking, generation and safe storage of hydrogen is another snag. This work addresses water lodging at cathode (a scaling issue) through a novel sinuous flow field both numerically and experimentally, by scaling up of PEMFC from 25 cm2 to 100 cm2. Conventional serpentine flow field of 25 cm2 widely studied in literature is experimented to validate the numerical model in a multiphysics tool. The model developed was applied to sinuous flow field of 25 cm2 and the results revealed better water removal and 7.7% higher power density than serpentine flow field due to inter channel diffusion and under rib convection. In order to increase power density further the dwell time at anode has to be increased in sinuous flow field, hence anode side flow field was made serpentine while retaining sinuous flow field at cathode. This combination enhanced the performance the power density by about 14%. This serpentine-sinuous combination was then scaled to 100 cm2 and experimented, revealing a lower power drop than serpentine flow field.

In quest of finding a sustainable solution for metal-free counter electrode materials, reduced graphene oxide (rGO) is emerged as the best alternative due to its intrinsic high electrocatalytic activity. However, owing to its two-dimensional sheets like structure, there is re-stacking of rGO sheets, which reduces exposed surface area and hinders in electrolyte diffusion. To avoid these issues, activated charcoal (AC) is explored as an active spacer material between rGO sheets, for the first time. By loading an optimum concentration of AC in rGO, a high porosity, high conductivity, and high concentration of active sites were gathered in the single composite structure. Such synchronized features of the proposed composite were utilized for Pt-free counter electrode application in dye-sensitized solar cell (DSSc). The composite structure showed high electrocatalytic activity, with a low charge transfer resistance of 0.7 Ω, which is far lower than Pt and rGO (8.5 Ω and 7.5 Ω). The DSSc fabricated with optimized composite showed power conversion efficiency of 8.6%, compared to Pt-based DSSc with 7.9% efficiency. Additionally, the potential of the electrode was also tested for the electro-photocatalytic (99%) degradation of methylene blue dye from water, in 60 min. The proposed highly efficient nanocomposite structure possesses the highest efficiency as compared to other previously studied rGO based counter-electrodes.

Large-scale production of H2 through water electrolysis is limited by the lack of efficient and crust-abundant low-cost electrocatalysts. Here, MoSe2 and N-doped carbon (NC) is successfully constructed into a double-shelled hierarchical hollow nanobox. The obtained NC@MoSe2 is demonstrated to be an active catalyst for hydrogen evolution reaction (HER). The NC@MoSe2 delicately combine the structural and functional advantages of two-dimensional layered transition metal dichalcogenides (TMDs) and NC, which yield the striking synergistic effect to endow them with extremely enhanced electrochemical activity to efficiently catalyze the evolution of H2. Remarkably, the NC@MoSe2 with the optimum thickness of MoSe2 shell can exhibit a fairly low onset potential of 61 mV, an extremely small overpotential of 164 mV vs. RHE at 10 mA cm−2, a greatly reduced Tafel slope of 55 mV dec−1, and a higher exchange current density of 0.102 mA cm−2. Specifically, this is mainly beneficial from the abundant exposed active edges from the edge-terminated ultrathin MoSe2 nanosheets with small size, the overall hierarchical hollow architecture and strong electronic coupling between MoSe2 and NC layer. Density functional theory (DFT) calculation results have well supported the experimental observations, revealing the strong synergistic effect between NC and MoSe2, thus the increased carrier density around the Fermi level and reduced hydrogen adsorption free energy (ΔGH*) for MoSe2 composited with NC.

Development of metal nitride-based thin film binder-free electrodes is a rapidly emerging area of research for the development of supercapacitors. The manganese nitride (Mn3N2) binder-free thin film electrodes were prepared using DC magnetron sputtering process. X-ray diffraction and the Raman spectroscopy characterization confirmed the formation of the tetragonal phase of Mn3N2 thin film. Field emission scanning electron microscopy revealed that the Mn3N2 particles are in nanoscale range and the particles with pyramidal shape are distributed uniformly on the surface of the film. Further, the Mn3N2 electrodes were examined by cyclic voltammetry and galvanostatic charge-discharge measurements to investigate the supercapacitive properties. The electrochemical measurements were performed on Mn3N2 deposited on conducting stainless steel substrates in different electrolytes (KOH, KCl and, Na2SO4 at 1 M concentration). The effect of various electrolytes on the areal capacitance, cycling stability, capacitance retention of the Mn3N2 electrodes was investigated. The Mn3N2 electrodes show high areal capacitance of 118 mF cm−2 for KOH, 68 mF cm−2 for KCl and 27 mF cm−2 for Na2SO4 at a scan rate of 10 mV/s. Moreover, the Mn3N2 electrodes indicated excellent cycling stability with capacitance retention of 98.5%, 89% and 83% for KOH, KCl, and Na2SO4, electrolytes respectively after 4,000 cycles. A comparative study on the electrochemical supercapacitive properties of the Mn3N2 electrode in different aqueous electrolytes is reported for the next generation electrochemical energy storage devices.

Two-dimensional nanostructured transition metal nitride-based thin film electrodes have been gaining importance in the electrochemical supercapacitor applications. In this work, Cr doped vanadium nitride (VN) thin films as an electrode material for high-performance supercapacitors have been demonstrated. In this study, reactive magnetron co-sputtering technique was adopted to fabricate phase pure VN as well as VN films doped with different Cr contents. These films were directly investigated as electrodes without using any additional binders. The phase purity and the surface chemistry of the Cr doped VN thin films were investigated using XRD and XPS techniques. Furthermore, EDS and X-ray elemental mappings were used to confirm the content of Cr and its distribution in these electrode films. The Cr −5.7 at. % doped VN thin film electrodes exhibited an extraordinary supercapacitor performance with the maximum areal capacitance of 190 mF/cm2 compared to the areal capacitance of 27 mF/cm2 for the un-doped VN at a scan rate of 10 mV/s. Moreover, the Cr-5.7 at. % doped VN thin film electrodes showed excellent electrochemical cycling stability and excellent reversibility with the capacitance retention of 92.4 %. It could be noticed that the incorporation of metal such as Cr could be a viable method to improve the electronic or ionic conductivity of the metal nitrides for supercapacitor applications.

Utilizing ultraviolet light by using Energy Down Shift (EDS) of quantum dots is a recent approach to efficiently utilize a broader spectrum of light, for energy harvesting. Other than higher efficiency, EDS is highly promising for increasing the stability of Dye-Sensitized Solar cells (DSSC); as it decreases the UV degradation of the cell. Previously, heavy metals-based (Cadmium etc) quantum dots are used for the purpose, which are not only toxic but also have less stability and have complicated synthesis methods. To overcome these issues, a thin coating of green emissive Nitrogen-doped Carbon Quantum Dots (N-CQDs) on DSSC, as a stable and efficient EDS layer is proposed here. N-CQDs were synthesized by a scalable, green and facile one-pot hydrothermal pyrolysis of citric acid in presence of nitrogen source, with a production yield of 65%, and quantum yield of 70%. The readily dispersible and highly stable colloid of N-CQDs was coated on the device, and with an optimized thickness, the power conversion efficiency was increased by 10%. This increase was further confirmed by external quantum efficiency (EQE) test, i.e. N-CQDs coated device showed EQE enhancement majorly in the UV spectrum and enhanced stability in UV light was recorded. The transmittance of FTO-glass was increased due to EDS and it also has an antireflection effect, which intern produces a small increase in EQE in the visible spectrum.

In the preparation of catalyst ink for proton exchange membrane fuel cell, the dispersing solvent has significant influence on the physicochemical and electrochemical properties of catalyst layer (CL), primarily due to the variation of the Nafion ionomer mobility. In this work, based on the Nafion mobility, the effect of solvent on water uptake (WU) behavior in the CL was investigated with respect to different solvents. To vary main- and side-chain mobilities of the Nafion ionomers, we consider different solvents such as glycerol, propylene glycol (PG), isopropyl alcohol (IPA), and N-methyl-2-pyrrolidinone (NMP). Experimental results demonstrated that the NMP CL showed the highest WU at 90% relative humidity, presenting 1.23, 1.27, and 1.28 times higher than that of the glycerol, PG, and IPA CL, respectively. Furthermore, the microstructure and phase images of the CLs revealed that the main-chain mobility governs the clustering behaviors among the Nafion agglomerates, whereas the side-chain mobility determines the ion-clustering behavior within the Nafion agglomerate. From the electrochemical performances, it was observed that the main- and side-chain mobility are related to the electrochemically active area and the proton-conduction pathway, respectively.

Size and shape tunable tin sulfide (SnS) thin film structures are successfully prepared by a simple cost-effective electrodeposition route. Scanning electron micrographs (SEM) effectively demonstrated the SnS shape modification. An ethylenediaminetetraacetic acid (EDTA) electrolyte was successfully used to alter the size of SnS. The SEM results also give evidence of the surface modification of SnS which was prepared with EDTA. Atomic force micrographs established the topological variations of SnS. Energy dispersive X-ray results confirmed the stoichiometric composition SnS prepared with and without EDTA. X-ray diffraction results revealed the polycrystalline orthorhombic structure of the SnS thin film. The optical band gap derived from the Tauc's plot was found to be in the 1.23–1.26 eV range. The near band edge emission peak for SnS was observed using photoluminescence properties. This simple strategy to synthesize a smooth, dense-packed and crack-free morphology could be an attractive way to produce SnS as a capable material for energy harvesting and optoelectronic devices.

In this research work, an attempt has been made to compare the performance and emission characteristics of n-butanol (n-B), iso-butanol (Iso-B), n-pentanol (P) and benzyl alcohol (Bn) with gasoline at various load conditions in the ratio of 10:90 by volume respectively, in a 2 cylinder SI test engine with MPFI technology. Alcohols were selected based on the position of hydroxyl (OH) group in its molecular structure, OH group was in straight chain for n-butanol and n-pentanol while it was branched chain for iso-butanol and finally OH group was chained with benzene ring for benzyl alcohol. The favorable outcome was that the performance of the fuel blends was noticeably higher than neat gasoline, with Bn10 blend giving greater fuel power at 100% load and P10, Bn10 and iso-B10 giving greater brake thermal efficiency. On the other hand, it was observed that the fuel consumption of n-B10 was higher than gasoline but iso-B10 gave lower fuel consumption comparatively. Considering pollutant emissions, all the blends gave lower HC, CO, & CO2 emissions as compared to neat gasoline, although the NOx emissions increased with increasing loads. Considering both performance and emission characteristics it was finally concluded that benzyl alcohol – gasoline blend was better compared to other blends.

The oxygen evolution reaction (OER) with sluggish kinetics is considered the bottleneck for developing clean and efficient H2 production from electrochemical water splitting. Exploring a high-efficient and good durability OER electrocatalyst to promote the reaction rate has drawn enormous attention. Herein, a particle-in-nanoplate architecture constructed by self-assembled Ni2.3FeP3.4 nanoparticles intertwined with the carbon nanotubes (Ni2.3FeP3.4/CNTs) is synthesized. The architecture of the resultant novel electrocatalyst Ni2.3FeP3.4/CNTs, which possesses the optimal balance of electrochemical active site, ion and electron conductivity, phosphorous content, delivers highly effective and stable electrocatalytic performance. In detail, as for OER, the Ni2.3FeP3.4/CNTs exhibits extraordinarily high-efficient with the smallest onset potential of ∼1.43 V vs. RHE, the lowest over-potential of 239 mV and 282 mV to reach the current densities of 10 and 100 mA cm−2, respectively, and the smallest Tafel slopes of 26.9 mV dec−1 in 1 M KOH. During 12 h galvanostatic electrolysis, the voltage is well maintained without any significant increase, representing a stable non-precious-metal catalyst for water oxidation. Moreover, a lower cell voltage of 1.523 V is achieved at a current density of 10 mA cm−2 by using it as a cathode in the overall water splitting. In addition, for the first time, the Ni2.3FeP3.4/CNTs is designed as an anode material for sodium ion batteries (SIBs). Consequently, the as-prepared Ni2.3FeP3.4/CNTs nanoarchitecture shows a high reversible capacity of 335.1 mAh g−1 at 100 mA g−1, excellent rate capability of 58.3 mA h g−1 under 10 A g−1, and stable long-term cycling performance.

Nitrogen-doped graphene quantum dots (N-GQDs) are emerging electroactive and visible light active organic photocatalysts, known for their high stability, catalytic activity and biocompatibility. The edge surfaces of N-GQDs are highly active, however, when N-GQDs make the film the edges are not fully exposed for catalysis. To avoid this issue, the N-GQDs are shaped to branched leaf shape, with an extended network of voids, offering highly active surfaces (edge) exposed for electrocatalytic and photocatalytic activity. The nitrogen doping causes a decrease in the bandgap of N-GQDs, thus enabling them to be superb visible light photocatalyst, for degradation of Methylene blue dye from water. Photoluminescence results confirmed that by a synergistic combination of the highly conductive substrate; Carbon fabric coated graphene sheets (CF-rGO) the recombination of photogenerated excitons is significantly suppressed, hence enabling their efficient utilization for catalysis. Comparatively, uniformly coated N-GQDs showed 49.3% lower photocatalytic activity, owing to their hidden active sites. The degradation was further boosted by 30% by combining the electrocatalytic activity, i.e. electro-photocatalysis of the proposed electrode. The proposed electrode material was analyzed using TEM, FE-SEM, FTIR, AFM, and WA-XRD, whereas the stability of electrode was confirmed by TGA, tensile test, bending test, and in harsh chemical environments. The proposed photo-electrocatalyst electrode is binder-free, stable, flexible and highly conductive, which makes the electrode quite suitable for flexible catalytic devices like flexible solar cells and wearable supercapacitors.

Two-dimensional material based heterostructures produce novel phenomena due to distinctive interactions between stacked layers. This paper details fabrication of van der Waals heterostructure consisting of layered MoS2 and WSe2 on FTO substrates by combining solution bath and radio-frequency sputtering. Raman scattering confirmed WSe2/MoS2 heterostructure formation, X-ray photoelectron spectroscopy surface profile detailed the heterostructure composition, and depth profile showed heterostructure interfacial structure with stacked WSe2 and MoS2 layers on the FTO substrate. Surface properties confirmed the WSe2/MoS2 heterostructure formed a multi-structured array of nanograins, and high resolution electron micrographs confirmed vertically formed layered fringes. Hydrogen evolution showed enhanced electrocatalytic behavior with 116 mV overpotential at 10 mA/cm2 and 76 mV/decade Tafel slope. Electrocatalytic property robustness was confirmed by over 20 h continuous hydrogen evolution reaction in an acidic solution. Enhanced electrocatalytic outcomes were due to increased interfacial hole-electron separation, dispersing active facets through the interface. The stacked layered structure provides a new avenue for two-dimensional heterostructures for energy harvesting devices.