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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.

Ceramic fuel cells possess tremendous advantages over PMFCs due to their fuel flexibility and requirement of low-purity hydrogen. Despite high conversion efficiency, the high cost of ultra high-purity hydrogen required for the operation limits the application of PMFCs. Although ceramic fuel cells operate at elevated temperature, high performance coupled with multifuel flexibility makes ceramic fuel cells a superior option as a static power source to generate electricity compared to thermal coal-fired power plants. BaZr1-x Y x O3-x/2 based protonic conductors get a high degree of interest due to their superior structural stability, but their poor conductivity at higher temperature limits the performance of ceramic fuel cells. To overcome the low ionic conductivity issues of BaZrO3 based materials at elevated temperature, the simultaneous doping of smaller Ga on the Zr site and K on the Ba site was employed here to create higher concentration of oxide-ion vacancies for the realization of superior conductivities. The simultaneous substitution of K and Ga created the oxygen vacancy-type point defects resulting in higher ionic conductivity ∼10-2 S/cm above 650 °C. The conductivity represented here for the Ba0.8K0.2Zr0.8Ga0.2O2.8 sample is superior or equivalent to the conductivity obtained for yttria-stabilized zirconia, a well-known ceramic oxide-ion electrolyte.

N, S-doped rGO was successfully synthesized and embedded Co-doped CeO2 via hydrothermal synthesis. The crystal structure, surface morphology and elemental composition of the prepared catalyst were studied by XRD, Raman spectra, SEM, TEM and XPS analyses. The synthesized electrocatalyst exhibits high onset and halfwave potential during the ORR. This result shows that a combination of N- and S-doped rGO and Co-doped CeO2 leads to a synergistic effect in catalyzing the ORR in alkaline media. Co–CeO2/N, S–rGO displays enhanced ORR performance compared to bare CeO2. The superior stability of the prepared catalyst implies its potential applications beyond fuel cells and metal–air batteries.

In this work, we developed a new molecularly imprinted polymer detector for tartrazine's rapid and selective detection. Electropolymerisation using l-Methionine resulted in the polymer immobilised on the carbon fibre paper electrode's surface. MIP film was formed by electropolymerisation in the presence of the template tartrazine. The polymer frame comprises cavities after template removal, which can specifically bind to the analyte molecule. Without pre-treatment, the developed sensor MIPMet/CFP detects tartrazine in beverage samples precisely and rapidly. The sensor has a linear response in the concentration range of 0.6 nM- 160 nM, high sensitivity (601964 µAµM

An approach, i.e., atmospheric-pressure nonequilibrium oxygen plasma jet technology, has been reported for the first time to in situ prepare ultrathin nonstoichiometric nickel oxide layers with mix...

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.

In recent years a renewed interest in developing iron electrode for iron based accumulators has risen, govern by the progress in nano-materials research that could bring iron based accumulators nearer to their theoretical energy density and capacity. In this aspect, Iron-Air battery chemistry is best suited for current energy crisis in combination with the cost effectiveness, eco-friendliness, recyclability, non-toxicity of the iron materials. The possibility of Iron-Air battery to function as a rechargeable battery makes this electrochemical systems for engaging development. However, some challenges related to the performance of iron electrode needs to be addressed such as the passivation of the iron electrode on discharge due to the accumulation of iron hydroxide and the low efficiency due to the parasitic hydrogen evolution that occurs during the charging. So the proper engineering and the formulation of iron electrodes are necessary to attain the maximum efficiency for Iron-Air battery. In this exertion, different Fe2O3/Carbon (Fe/C) composites are tested as electrodes for Iron air battery. In addition to this, the prepared materials were comprehensively characterized by X-ray diffraction (XRD). The electrochemical effectiveness of the prepared samples were tested in a three electrode configuration.Fe2O3/MWCNT electrode show the best electrochemical performance exhibits a specific capacity of about 350 mAhg−1 at 10 mA cm−2 compared to the Fe2O3/Graphene of 300 mAhg−1, Fe2O3/Acetylene black of 225 mAhg−1 and Fe2O3/Vulcan carbon of 180 mAhg−1.

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.