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Au nanoparticles of size ranging 2–6 nm were deposited over hexagonal CdS using three conventional metal deposition methods namely; deposition precipitation (DP), incipient wet impregnation (WI), photo-deposition (PD) and a recently reported KI method by our group [1]. The later involves reduction of Au 3+ ions with iodide ions. XRD results confirmed the formation of CdS hexagonal phase from as prepared cubic phase at 600 °C under the N 2 atmosphere. Transmission electron spectroscopy (TEM), diffused reflectance spectroscopy (DRS), X-Ray fluorescence (XRF), ICP-OES and photoreactions were conducted to study the effect of Au particle size, Au loading and Au plasmonic properties on H 2 production activity. It was found that surface plasmon resonance (SPR) is directly linked to Au particle size. Among all four methods, 3 wt.% Au deposited over hexagonal CdS by KI method with mean Au particle size of 4 nm showed highest performance for hydrogen production from water electrolyte mixture under visible light irradiation (>420 nm and a flux of 35 mW/cm 2 ). XPS results of Au/CdS prepared by KI method showed that Au is exclusively present in zero oxidation state before and after photocatalytic H 2 production testes indicating the stable nature of Au/CdS catalyst. The H 2 production activity of Au/CdS catalysts prepared by different metal deposition methods and H 2 production mechanism in a water-electrolyte is discussed in detail. [ABSTRACT FROM AUTHOR]

A series of Cu(OH)2-Ni(OH)2/P25 photocatalysts was prepared by co-deposition-precipitation (total metal loading ≈1 wt %) and their performance was evaluated for H2 production. Among this series, the 0.8 Cu(OH)2-0.2 Ni(OH)2/P25 photocatalyst demonstrated very high H2 production rates in 20 vol % ethanol/water and 5 vol % glycerol/water mixtures (10 and 22 mmol h−1 g−1, respectively). Detailed analyses based on reaction kinetics, photoluminescence, X-ray photoelectron spectroscopy (XPS), and charge carrier scavenging suggest that both working catalysts are composed of Cu and Ni metals in their active phases. Cu0 is produced directly by the transfer of electrons from the conduction band of TiO2 to surface Cu(OH)2 nanoclusters, whereas Ni0 is formed indirectly through a process of gradual dissolution of Ni(OH)2 to yield aqueous Ni2+ owing to the acidic environment of the medium, followed by Ni2+ reduction by electrons from the TiO2 conduction band. The high rates of H2 production that match those obtained with noble metals can be explained owing to a considerably less negative Δ Go of Cu oxide formation when compared with that of Ni oxide formation and higher work function of Ni than that of Cu. [ABSTRACT FROM AUTHOR]

Synthesis of mixed transition metal nitrides often leads to the formation of more than one phases in the final product. A control over molar ratio of metals (Fe:Ni) along with synthetic strategy is used to form phase pure product (Fe 3 Ni 7 N@C). The synthesized material is used as an efficient and cost-effective electrocatalyst for oxygen evolution reaction (OER). Fe 3 Ni 7 N@C requires a low overpotential of 290 mV to achieve a catalytic current density of 10 mA cm−2 which holds Tafel slope of 40 mV dec−1 superior to the noble metal benchmark catalysts. The physicochemical integrity of Fe 3 Ni 7 N@C is maintained up to 12 h activity as evident from post catalytic characterization. Fe3Ni7N@C nanoparticles for oxygen evolution reaction. [Display omitted] • A control over molar ratio of metals (Fe:Ni) is used to form phase pure product (Fe 0.3 Ni 0.7 N@C). • Fe 0.3 Ni 0.7 N@C is used as an efficient electrocatalyst for oxygen evolution reaction (OER). • Fe 0.3 Ni 0.7 N@C requires a low overpotential of 290 mV to achieve a catalytic current density of 10 mA cm−2. • The physicochemical integrity of Fe 0.3 Ni 0.7 N@C is maintained up to 12 h activity. [ABSTRACT FROM AUTHOR]

The conversion of solar to chemical energy is one of the central processes considered in the emerging renewable energy economy. Hydrogen production from water splitting over particulate semiconductor catalysts has often been proposed as a simple and a cost-effective method for large-scale production. In this review, we summarize the basic concepts of the overall water splitting (in the absence of sacrificial agents) using particulate photocatalysts, with a focus on their synthetic methods and the role of the so-called "co-catalysts". Then, a focus is then given on improving light absorption in which the Z-scheme concept and the overall system efficiency are discussed. A section on reactor design and cost of the overall technology is given, where the possibility of the different technologies to be deployed at a commercial scale and the considerable challenges ahead are discussed. To date, the highest reported efficiency of any of these systems is at least one order of magnitude lower than that deserving consideration for practical applications. [ABSTRACT FROM AUTHOR]

Photoreforming biomass-derived waste such as glycerol into hydrogen fuel is a renewable hydrogen generation technology that has the potential to become important due to unavoidable CO2 production during methane steam reforming. Despite tremendous efforts, the challenge of developing highly active photocatalysts at a low cost still remains elusive. Here, we developed a novel photocatalyst with a hybrid support comprising reduced graphene oxide (rGO) and TiO2 nanorods (TNR). rGO in the hybrid support not only performed as an excellent scavenger of electrons from the semiconductor conduction band due to its suitable electrochemical potential, but also acted as an electron transport highway to the metal co-catalyst, which otherwise is not possible by simply increasing metal loading due to the shadowing effect. A series of hybrid supports with different TNR and rGO ratios were prepared by the deposition method. Pd nanoparticles were deposited over hybrid support through the chemical reduction method. Pd/rGO-TNRs photocatalyst containing 4 wt.% rGO contents in the support and 1 wt.% nominal Pd loading demonstrated hydrogen production activity ~41 mmols h−1g−1, which is 4 and 40 times greater than benchmark Au/TiO2 and pristine P25. The findings of this works provide a new strategy in optimizing charge extraction from TiO2, which otherwise has remained impossible due to a fixed tradeoff between metal loading and the detrimental shadowing effect. [ABSTRACT FROM AUTHOR]

Non-noble metal containing catalysts for oxygen reduction reaction (ORR) are being targeted due to their low cost and availability. The rarity, high-cost, and self-poisoning of noble metals are the main drawbacks for the large-scale applications. Herein, a facile and simple synthetic strategy is adopted to prepare non-noble metal-based nitrogen doped carbon nanotubes (N-CNTs). The cobalt oxides (CoOx) nanoparticles are in-situ encapsulated inside these N-CNTs which are then treated with acid (HCl) and phosphidized to obtain CoOx-CoP/N-CNTs. High resolution transmission electron spectroscopy (HR-TEM) results reveal that the ends of N-CNTs are closed with nanoparticles. X-ray photoelectron spectroscopy (XPS) confirms the presence of cobalt oxide and cobalt phosphide nanoparticles. The catalyst CoOx-CoP/N-CNTs2 demonstrated E onset and E 1/2 of 0.96 V and 0.81 V, respectively in alkaline environment which is very much comparable to the state of art catalyst (20 wt% Pt/C). Acid treatment significantly enhances the electrocatalytic activity for ORR in comparison to material synthesized without prior treatment with acid. The catalyst exhibits excellent durability over 10,000 cycles and methanol tolerance to 0.5 M methanol addition. The enhanced ORR activity is attributed to synergistic effect of carbon matrix and encapsulated nanoparticles. • Cobalt oxides (CoOx) nanoparticles are in-situ encapsulated inside N-CNTs. • CoOx/N-CNTs treated with acid (HCl) and phosphidized to obtain CoOx-CoP/N-CNTs. • High resolution transmission electron spectroscopy results reveal that the ends of N-CNTs are closed with nanoparticles. • CoOx-CoP/N-CNTs2 demonstrated E onset and E 1/2 of 0.96 V and 0.81 V, respectively in alkaline environment. • The catalyst exhibited excellent durability over 10,000 cycles and methanol tolerance to 0.5 M methanol addition. [ABSTRACT FROM AUTHOR]

The article describes the conversion of MOF-199 to Cu–Cu 2 O–CuO/C 700 ( 1 ) and Cu–Cu 2 O–CuO/C 800 ( 2 ) nanostructures by simple pyrolysis at 700 and 800 °C under inert atmosphere. The X-ray photoelectron spectroscopy analysis reveals that the nanostructures Cu–Cu 2 O–CuO/C consist of graphitic carbon functionalized with carboxylic, carbonyl and hydroxyl functional groups with copper/copper oxide particles on surfaces. The electrochemical properties of 1 and 2 are evaluated as electrode material for supercapacitors using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results for the capacitive performance from cyclic voltammetry and galvanostatic charge/discharge reveal that both the samples have gravimetric capacitance greater than 750 F g −1 at a scan rate of 2 mV s −1 and current density of 2 mA cm −2 . The samples retain about 43% of their initial capacitance even at high scan rate of 75 mV s −1 . The cycling performance of the nanostructures illustrate that there is 5.5% capacitance loss after 3000 cycles. The sample 1 and 2 are washed with 1 mol L −1 HCl solution to obtain copper oxide free materials Cu/C 700 ( 3 ) and Cu/C 800 ( 4 ). Samples 3 and 4 are tested as electrocatalysts for glucose sensing and the cyclic voltammetry measurement shows enhanced current densities compared to the literature values. [ABSTRACT FROM AUTHOR]

Graphitic carbon material encasing chromium oxide nanoribbons [Cr 2 O 3 –C composite] is obtained by carbonizing a mixture of furfuryl alcohol and Cr-BDC MOF [BDC: benzene dicarboxylic acid; Cr 3 F(H 2 O) 2 O[(O 2 C)C 6 H 4 –(CO 2 )] 3 ·nH 2 O] at 900 °C under inert atmosphere. The Ni–Pd nanoparticles synthesized by NaBH 4 reduction method are loaded on the Cr 2 O 3 –C support via sonication. Morphological, structural, and chemical analysis of the designed chromia based carbon support and synthesized nanoparticles is carried out with PXRD, EDX, SEM, HR-TEM and BET surface area. The gas adsorption analyses reveal that BET surface area of Cr 2 O 3 –C support decreases from 438 m 2 g −1 to 171 m 2 g −1 by the incorporation Ni–Pd nanoparticles. The electro-oxidation reaction of methanol is carried out over the designed electrocatalysts in acidic media. The Ni–Pd nanoparticles supported on Cr 2 O 3 –C have presented a significant increase in catalytic activity for methanol oxidation and tolerance in comparison to the nanoparticles supported on activated carbon and glassy carbon electrode. [ABSTRACT FROM AUTHOR]