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In this study, we have synthesized hierarchical TiO2@In2O3 heteroarchitecture photoanodes via a hydrothermal method and studied their interfacial charge carrier dynamics through water splitting and organic decomposition. Photoelectrochemical measurements show that the IN-0.4 exhibits an obvious enhancement in photocurrent density compared to the pristine TiO2. Electrochemical impendence spectroscopy (EIS) and Time-resolved photoluminescence (PL) have been employed to study the charge recombination in TiO2@In2O3 nanostructure. The surface passivation of TiO2 nanorods (NRs) with In2O3 nanostructures helps to the suppression of the surface defects. The surface-passivated photoanode (IN-0.4) has demonstrated the improved hydrogen generation activity (125 μmol∙h−1) of TiO2 nanorods (NRs) with In2O3 nanostructures during water splitting and organic decomposition. The probable causes of the enhancement in hydrogen evolution could be due to (i) enhanced photogenerated electron transport (ii) increased active surface area with In2O3 and/or (iii) catalytic activity of In2O3. Moreover, the photoelectrocatalytic activities of IN-0.4 were slight affect during degradation of Bisphenol A and methyl orange dye, which might be due to the lower hole mobility in TiO2@In2O3 heteroarchitecture photoelectrodes. These sightings and proposed schematic model can help to understand the charge transfer dynamics in hierarchical TiO2@In2O3 heteroarchitecture photoelectrodes as well as designing multifaceted photoelectrodes for solar energy conversion.

In recent years, Fe-based catalysts for the selective catalytic reduction of NO with NH3 (NH3-SCR) have been attracting more attention. In this work, a novel Fe-Sb binary metal oxide catalyst was synthesized using the ethylene glycol assisted co-precipitation method and was characterized using a series of techniques. It was found that the catalyst with a molar ratio of 7:3 (Fe:Sb) displayed the best NH3-SCR activity with 100% conversion of NOx (nitrogen oxides) over a wide temperature window and with good resistance to H2O + SO2 at 250 °C. The X-ray photoelectron spectroscopy (XPS) and in situ diffused reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) of NOx adsorption results suggested that strong electron interactions between Fe and Sb in Fe-O-Sb species existed and electrons of Sb could be transferred to Fe through the 2Fe3+ + Sb3+ ↔ 2Fe2+ + Sb5+ redox cycle. The introduction of Sb significantly improved the adsorption behaviour of NOx species on the Fe0.7Sb0.3Ox surface, which benefitted the adsorption/transformation of NOx, thereby facilitating the NH3-SCR reaction. In addition, the Fe0.7Sb0.3Ox catalyst demonstrated a good tolerance of H2O and SO2, since the decomposition of NH4HSO4 on the catalyst surface was promoted by the introduction of Sb.

In present work, we synthesized ZnFe2O4 nanorods on a fluorine-doped tin oxide substrate using spray coating method followed by two-step high-temperature quenching (HTQ). X-ray photoelectron spectroscopy (XPS) results indicate that Sn4+ is diffused from the FTO substrate after the second quenching, which could help in minimizing the recombination of photogenerated carriers. Photoelectrochemical measurements of the ZnFe2O4 nanorod photoelectrodes quenched at 780 °C, 800 °C, and 820 °C indicate that among the studied samples (ZFO1, ZFO2 and ZFO3), the highest photocurrent density was observed for nanotextured ZFO3 photoelectrodes (130 µA cm−2 at 1.23 V vs RHE). The photoelectrochemical performances of the ZnFe2O4 nanorods after the second quenching were compared with those of the firstly quenched ZnFe2O4 nanorod samples; water-oxidation photocurrent density of the former (ZFO3) was increased by 6.9 times compared with that of the first quenching (PZFO). Intensity modulated photocurrent spectroscopy (IMPS) and photoluminescence (PL) results confirm the faster charge extraction was achieved for the ZFO3 photoelectrode. Thus, the overall photocurrent density during the second quenching process results from the effectively improved crystallinity, the reduced strain and suppressed charge–carrier recombination's on both the surface as well as in the bulk of the ZnFe2O4 nanorods. In terms of solar water splitting, these research findings provide an effective route for the synthesis of other nanostructures.

Highly efficient photoelectrochemical (PEC) hydrogen production is achieved using p-Si wire arrays loaded with NiMoZn particles in aqueous sulfuric acid under simulated sunlight (AM 1.5 G; 100 mW cm −2 ). Vertically-aligned wire arrays are grown on planar Si wafers via a quick electroless etching process within 5 min, leading to short Si wires of ∼4 μm and diameters of ∼0.2 μm. Despite the short length of the wires, the reflectance of the arrays is I ph ) is enhanced by ∼ 30% relative to planar Si. To further improve the PEC performance, ∼ 100 nm NiMoZn particles are photoelectrochemically deposited onto the wires. The wire arrays with evenly distributed NiMoZn particles show a photocurrent onset potential (E on ) of ∼ + 0.27 V vs. RHE and produce an I ph of ∼1.45 mA cm −2 at 0 V vs. RHE with a Faradaic efficiency of ∼ 100% for H 2 evolution. This I ph value is ∼10-fold greater than that with the planar Si/NiMoZn samples. The excellent performance of the wire arrays and NiMoZn heterojunction is attributed to enhanced light absorption (decreased reflectance), facilitated charge transfer (radial-directional electron transfer), and NiMoZn-catalyzed hydrogen production.

© 2017 Elsevier B.V. Sunlight-driven conversion of hexavalent uranium (U(VI)) in seawater is achieved with mixed p-type CuO and CuFeO2(CuO/CuFeO2) photocatalyst film electrodes synthesized via electrodeposition (ED) of Cu(II) and Fe(III), followed by annealing in air. The mixed photocatalysts exhibit a double-layer configuration with crystalline structures of CuO and CuFeO2. On irradiation of the CuO/CuFeO2electrodes (held at −0.5 V vs. SCE) with solar simulated light (air mass 1.5; 100 mW cm−2), the U(VI) concentration decreases with time, while the total amount of uranium in solution does not change. This indicates that virtually all conversion reactions of U(VI) occur in the bulk solution, while surface reactions are limited due to insignificant adsorption of U(VI). U(VI) conversion leads to the mixed production of lower oxidation states U4+, U14/3+, and U16/3+at a ratio of 42:28:30, with an overall Faradaic efficiency of ∼98%. The kinetics and induction time for U(VI) conversion are significantly influenced by the conditions of photocatalyst synthesis (CuO/CuFeO2, CuO, and CuFeO2; ED times of 2–4 h), the applied potential value (−0.4, −0.5, and −0.6 V vs. SCE), and the seawater condition (air-equilibrated vs. N2-purged; pH 3–10.4). Based on the obtained results, O2is proposed to play a key role in shuttling photogenerated electrons between the electrodes and U(VI). In addition, the existence of an induction time is discussed in terms of material and reaction pathway.

© 2018 The Royal Society of Chemistry. A novel sunlight-water-energy nexus technology is presented that combines the photoelectrocatalytic (PEC) desalination of saline water and desalination-driven wastewater remediation coupled with the production of molecular hydrogen (H2) from water. To accomplish this, morphologically tailored TiO2 nanorod (TNR) and hydrogen-treated TNR (H-TNR) array photoanodes are placed in an anode cell and Pt foils are located in a cathode cell, while a middle cell containing saline water (0.17 M NaCl) faces these cells through anion and cation exchange membranes, respectively. Upon irradiation by simulated sunlight (AM 1.5G, 100 mW cm-2), the photogeneration of charge carriers initiates the transport of chloride and sodium in the middle cell to the anode and cathode cells, respectively, leading to the desalination of saline water. The chloride in the anode cell is converted to reactive chlorine species (RCS), which effectively decompose urea to N2 as a primary product (>80%), while the sodium in the cathode cell accelerates the H2 production from water with a Faradaic efficiency of ∼80%. The PEC performance of the H-TNR photoanodes is superior to that of the TNR in the anodic and cathodic processes because of the reduced charge transfer resistance and sub-nanosecond charge transfer kinetics (∼0.19 ns), leading to a specific energy consumption of 4.4 kW h m-3 for 50% desalination, with an energy recovery of ∼0.8 kW h m-3. The hybrid system is found to operate for a period of ∼60 h with natural seawater, and virtually all the photoanodes are shown to be capable of driving the hybrid process. Although tested as a proof-of-concept, the present technology opens up a novel field involving a sunlight-water-energy nexus, promising high efficiency desalination and the desalination-driven remediation of water with simultaneous H2 production.

Facile synthesis of efficient electrocatalysts that can selectively convert CO2 to value-added chemicals remains a challenge. Herein, the electrochemical synthesis of porous Bi dendrite electrodes and details of their activity toward CO2 conversion to formate in aqueous solutions of bicarbonate are presented. The as-synthesized multilayered, porous, dendritic Bi electrodes exhibit a faradaic efficiency (FE) of approximately 100 % for formate production. Added halides and cations significantly influence the steady-state partial current density for formate production JFM (Cl?>Br??I?; Cs+>K+>Li+). DFT calculations revealed that the reaction pathway involving the species *OCOH occurs predominantly and the presence of both Cs+ and Cl? makes the overall reaction more spontaneous. Photovoltaic-cell-assisted electrocatalysis produced formate with an FE of approximately 95 % (JFM?10 mA cm?2) at an overall solar conversion efficiency of approximately 8.5 %. The Bi electrodes maintain their activity for 360 h without a change in the surface states. - 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Scopus