Search

This is the first comprehensive review of the impact of water impurities on PEM, AEM, and alkaline water electrolysers.

Hollow structures made of nanoscale building blocks are of great interest as catalysts for electrochemical water splitting. Here we report a solution-phase synthesis of yolk–shell Co3O4/Co1−xRuxO2 microspheres (MSs) having a shell made of Co1−xRuxO2 nanorods and the core of Co3O4. Benefiting from the peculiar morphology and the synergy between the different materials present in the MSs, the latter exhibit enhanced electrochemical oxygen evolution activity and long-term stability in acidic media. The catalyst achieves a catalytic current density of 10 mA cm−2 at an overpotential of only 240 mV, a small Tafel slope of 70 mV dec−1, and a high mass activity of 600 A g−1 and maintains its activity throughout a 24 h chronopotentiometry tests at constant current densities of 10 and 20 mA cm−2.

Pt nanoparticles deposited on mesoporous carbon (Pt/C) represent a benchmark catalyst for the hydrogen evolution reaction (HER) in both acid and alkaline conditions. However, it shows an order of magnitude lower activity under alkaline media compared to acid media. Moreover, the activity of this catalyst decreases rapidly under operational conditions due to both migration and aggregation of the metal particles, leading to a rapid decline in the number of active sites. We show here a Cu and Ru-based catalyst fabricated by slow electrodeposition of Ru onto a nanostructured Cu layer grown, in turn, on the top of a Ti substrate. Our catalyst has a high and stable HER activity, outperforming the benchmark Pt/C catalyst under alkaline conditions. The high activity and prolonged stability are attributed to the peculiar structure of our electrode, in which Cu nanoplates are directly attached perpendicular to the Ti substrate, providing a high surface area support onto which Ru nanocrystals are bound. This makes the Cu–Ru/Ti electrode one of the most active (−10 mA cm2 of HER current at only −23 mV overpotential) and stable electrocatalysts (no activity degradation for 100 h at −0.2 V) reported to date for the alkaline hydrogen evolution reaction.

The engineering of the structural and morphological properties of nanomaterials is a fundamental aspect to attain desired performance in energy storage/conversion systems and multifunctional composites. We report the synthesis of room temperature-stable metallic rutile VO

Water electrolysis is one of the most promising methods to produce H2 and O2 as high potential fuels. Comparing the two half-reactions, the oxygen evolution reaction (OER) is the more difficult to be optimized and still relies on expensive noble metal-based catalysts such as Ru or Ir. In this paper, we prepared nanoparticles of HfN and Hf2 ON2 and tested them for the OER for the first time. The HfN sample, in particular, showed the highest activity, requiring an overpotential of only 358 mV at 10 mA cm-2 in Fe-free electrolyte and, above all, exhibiting long-term stability. This result places this system amongst one of the most promising catalysts for OER tested to date, in terms of sustainability, activity and stability. The prepared nanoparticles are small (less than 15 nm in diameter), well-defined in shape and crystalline, and were characterised before and after electrochemical testing also via electron microscopy (EM), powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS).

The electrocatalytic oxygen evolution reaction (OER) is an important half reaction in various technologies, such as metal air batteries and electrochemical water splitting. Transition metal chalcog...

Nickel and cobalt-based chalcogenides are an interesting class of electrochemically active compounds. Herein we report a two-step synthesis of uniform hollow nickel cobalt perselenide nanostructured microparticles with a corrugated surface, randomly spaced pores, and a tunable composition. In the first step, we synthesized Ni–Co acetate hydroxide prism-shaped microparticles, which were subsequently used as templates for the selenization process at temperatures as low as 80 °C. The substitution of acetate and hydroxide anions with selenide anions at a low temperature eventually produced partially amorphous hollow microparticles due to the nanoscale Kirkendall effect. Thin films of the as-synthesized samples behaved as highly active catalysts for the electrochemical oxygen evolution reaction (OER). Among those, Ni0.88Co1.22Se4 hollow microparticles showed excellent performances, exhibiting a 10 mA/cm2 current density at a modest overpotential of 320 mV, a high turnover frequency of 0.146 S1–, and a long-ter...

We synthesized two new terpyridine based Ru sensitizers (SY-01 and SY-02) with the lowest unoccupied molecular orbital (LUMO) levels of these two dyes are well-matched with that of the black dye (N749). Both sensitizers capable of exhibiting metal-to-ligand charge transfer band show a higher molar extinction coefficients (e ∼ 5.0–6.8 × 103 M−1 cm−1) than that (4.2 × 103 M−1 cm−1) of N749 because of the enhanced absorption arising from thiophene moiety. Density functional theory calculations reveal that LUMOs of SY-01 and SY-02 are distributed over the terpyridine and thienyl moieties. The excited-state oxidation potentials, E°ox*, obtained by the electrochemical studies, range from −0.98 to −0.96 V, are sufficiently more negative than the conduction band edge of the TiO2 electrode (ca.−0.5 V). The increased conjugation conferred to SY-01 and SY-02 dyes through π-expansion by thiophene moiety increases light-harvesting and energy conversion efficiency in comparison with N749.

In the present investigation, in addition to pseudocapacitor application, the growth of interconnected nanorods/nanoplates of nickel sulfide (NiS) on a titanium (Ti)-substrate has been explored. An additive-free synthesis is performed by using a simple chemical bath deposition method. Structure and morphology of as-prepared NiS films are characterized by various characterization techniques such as X-ray diffraction, field effect scanning electron microscopy, high resolution transmission electron microscopy, and selected area electron diffraction etc. Electrochemical properties of the NiS thin film electrodes are studies by means of cyclic voltammetry and galvanostatic charge–discharge spectra obtained in 1 M aqueous KOH electrolyte. The NiS electrode demonstrates the notable pseudocapacitive activities including high specific capacitance (788 F g−1 at 1 mA cm−2), good rate capability (640 F g−1 at 50 mA cm−2), excellent cycling stability (98% retention after 1000 cycles) and high energy density (27.4 W h kg−1) as well as good power density (3.05 kW kg−1). Such an empirical performance is mostly due to the interconnected-type surface of NiS, which provides fast electron and ion transport. The obtained results indicate that the NiS thin film is a capable candidate as an electrode material for supercapacitor application.

We report an interesting case of in situ dynamic nanostructuring of catalyst and support under hydrogen evolution conditions in basic media. When solution-grown CuO nanoplates on titanium substrates are subjected to hydrogen evolution reaction, besides the reduction of CuO to metallic Cu nanoplates, both catalyst and support simultaneously undergo a nanostructuring process. The process is driven by the dissolution-redeposition of Cu and the alkaline etching of the titanium support. The morphology of the resulting nanocomposite material consists of a porous matrix made of ultrasmall Cu nanocrystals and amorphous TiOx nanoparticles. Interestingly, the nanostructuring of the catalyst can be finely controlled by varying the applied potential. Such a process leads to a 5.4-fold improvement in the catalyst activity, which is attributed not only to its large active surface area (formed upon nanostructuring), but also to an improved water dissociation activity, provided by the in situ formation of TiOx nanoparticles. The final catalyst exhibits -10 mA/cm2 of current density at a small overpotential of -108 mV and a long-term operational stability up to 50 h. Density functional theory calculations show that the co-presence of Cu and TiO2 nanoparticles optimizes the free energy of hydrogen adsorption in the final catalyst. Our work highlights the importance of studying the dynamic evolution of catalysts under operational conditions and choice of proper support that enhances the catalyst activity.

Here we report functionalized multiwalled carbon nanotubes (f-MWCNTs)-CdSe nanocrystals (NCs) as photosensitizer in photoelectrochemical cells, where f-MWCNTs were uniformly coated with CdSe NCs onto SnO2 upright standing nanosheets by using a simple electrodeposition method. The resultant blended photoanodes demonstrate extraordinary electrochemical properties including higher Stern-Volmer constant, higher absorbance, and positive quenching, etc., caused by more accessibility of CdSe NCs compared with pristine SnO2-CdSe photoanode. Atomic and weight percent changes of carbon with f-MWCNTs blending concentrations were confirmed from the energy dispersive X-ray analysis. The morphology images show a uniform coverage of CdSe NCs over f-MWCNTs forming a core-shell type structure as a blend. Compared to pristine CdSe, photoanode with f-MWCNTs demonstrated a 257% increase in overall power conversion efficiency. Obtained results were corroborated by the electrochemical impedance analysis. Higher scattering, more accessibility, and hierarchical structure of SnO2-f-MWCNTs-blend-CdSe NCs photoanode is responsible for higher (a) electron mobility (6.89 × 10(-4) to 10.89 × 10(-4) cm(2) V(-1) S(1-)), (b) diffusion length (27 × 10(-6))

Low-temperature wet chemical method has been applied to produce indium oxide (In 2 O 3 ) nanostructures viz. cracked-cubes and the maize-corns which were then employed for their structure, morphology and surface-related measurements and finally envisaged in detection of liquefied petroleum gas (LPG) at different temperatures and concentrations. At 1000 ppm LPG, cracked-cube-based In 2 O 3 sensor demonstrated lower operating temperature (135 °C) and gas sensitivity (44.35%) than the maize-corn-type (155 °C, 36.51%). Except moderate difference in sensitivity there was negligible difference in response and recovery periods.

Nanostructured thin films of metal sulfides (MS) are highly desirable materials for various optoelectronic device applications. However, a general low-temperature protocol that describes deposition of varieties of MS structures, especially in their film form is still not available in literatures. Here, a simple and highly effective general solution-based deposition protocol for highly crystalline and well-defined nanostructured MS thin films from ethanol on variety of conducting and non-conducting substrates is presented. The films display remarkable electronic properties such as high carrier mobility and high conductivity. When NiS thin film deposited on a flexible polyethylene terephthalate (PET) substrate is used as a fluorine doped tin oxide (FTO)-free counter electrode in dye-sensitized solar cells, it exhibits a solar-to-electric power conversion efficiency of 9.27 ± 0.26% with the highest conversion efficiency as high as 9.50% (vs 8.97 ± 0.07% exhibited by Pt-electrode). In addition, the NiS film deposited on a Ti-foil has demonstrated an outstanding catalytic activity for the hydrogen and oxygen evolution reactions from water.

In the present work, porous 3D CdO-microstructured electrode obtained by pyrolysis of 3D CdCO3 microstructures is self-sensitized with CdSe using an ion exchange reaction. After sensitization, an interfacial treatment of the CdO-CdSe interface is performed by depositing a thin film of PEDOT using a photoinduce polymerization route. The microstructured electrode before and after interfacial treatment is characterized using field-emission scanning microscope, energy dispersive X-ray analyzer, contact angle measurement, UV-Visible absorption spectrophotometer and X-ray photoelectron spectrometer. After constructing a liquid junction solar cell with a Pt counter electrode, the photovoltaic performance and interfacial charge transfer kinetics across the CdO-CdSe interface before and after PEDOT treatment are investigated. The results exhibit an improved interfacial charge-transfer resistance after the PEDOT treatment, which leads to enhance the short-circuit current by 15.81% and the power conversion efficiency by 19.82%.

We studied the effect of the hole transport layer (HTL) thickness on photovoltaic properties of meso-superstructured perovskite solar cells based on CH3NH3PbI3−xClx. We found that there is an interplay between photovoltaic performance and reproducibility: thinning the HTL increased performances of the devices but reduced their reproducibility.

Based on a coordination chemistry approach, the present work reports on the synthesis of thin films of various cobalt hydroxycarbonate nanostructures such as nanobeams, nanoneedles, and bending nanorods using three different cobalt precursors viz. Cl−, NO3− and CH3COO−. After pyrolysis in air, the hydroxycarbonate nanostructures are transferred into 1-D arrays of Co3O4 nanorods. The obtained 1-D Co3O4 nanostructures are then transformed into the corresponding analogous shaped 1-D arrays of porous cobalt sulfide (CoS1.0365) nanostructures using a wet chemical transformation method based on an ion exchange approach. The nanostructured films before and after the ion exchange reaction are characterized using field emission electron scanning microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), and inductively coupled plasma mass spectroscopy (ICP-MS) measurements. As a proof-of-concept demonstration for the application, various shaped CoS1.0365 nanorod films synthesized are investigated as a Pt-free counter electrode in dye-sensitized-solar cells (DSSCs). The influence of three different counter anions of the cobalt precursors on the structural, textural, and morphological aspects, and thereby their influence on electronic and electrochemical properties, has been investigated. A correlation among electrical conductivity, charge transfer resistance and electrocatalytic performance of various CoS1.0365 nanorod films obtained from different cobalt precursors has been established. Among the various nanostructures, the thicker nanorod film synthesized using a chloride precursor has demonstrated the best electrocatalytic behavior toward triiodide reduction, which led to a short circuit current density of 18.04 mA cm−2 and energy conversion efficiency of 7.4% of the DSSC. This photovoltaic performance is highly competitive to a current density of 18.26 mA cm−2 and energy conversion efficiency of 7.7% exhibited by the standard Pt counter electrode.

DSSCs synergic effect, for reducing charge recombination and energizing charge transfer, in SnO2 photoanodes functionalized with thin layers of several metal oxides including ZrO2, MgO, CaCO3 and ZnO etc., for boosting overall dye-sensitized solar cells (DSSCs) performance is investigated. The SnO2 photoanodes composed with upright-standing nanosheets were initially fabricated using a simple and cost-effective wet chemical method. Both pristine and functionalized SnO2 photoanodes were explored in DSSCs application in addition to other photoelectrochemical properties where, functionalized photoanodes exhibited remarkably improved light-to-electrical power conversion efficiencies compared to that of pristine one. To corroborate synergic effect and for probing the charge transport properties including charge transfer resistance and electron life time in thin metal oxide functionalized SnO2 photoanodes, electrochemical impedance spectroscopy measurement was undertaken.

We investigate the stability of an active organometallic perovskite layer prepared from a two-step solution procedure, including spin coating of aqueous lead nitrate (Pb(NO3)2) as a Pb2+ source and sequential dipping into a methylammonium iodide (CH3NH3I) solution. The conversion of CH3NH3PbI3 from a uniform Pb(NO3)2 layer generates PbI2-free and large-grain perovskite crystallites owing to an intermediate ion-exchange reaction step, resulting in improved humidity resistance and, thereby, improved long-term stability with 93% of the initial power conversion efficiency (PCE) after a period of 20 days. The conventional fast-converted PbI2-dimethylformamide solution system leaves small amounts of intrinsic PbI2 residue on the resulting perovskite and MAPbI3 crystallites with uncontrollable sizes. This accelerates the generation of PbI2 and the decomposition of the perovskite layer, resulting in poor stability with less than 60% of the initial PCE after a period of 20 days.

In this work, we demonstrate an extremely simple but highly effective strategy for the synthesis of various functional metal oxides (MOs) such as ZnO, In2O3, Bi2O3, and SnO2 nanoparticles with various distinct shapes at room temperature via a solid-state reaction method. The method involves only mixing and stirring of the corresponding metal salt and NaOH together in the solid phase, which yields highly crystalline metal oxides within 5–10 min of reaction time. The obtained paste can be directly doctor-bladed onto a variety of substrates for photoelectrochemical applications. The crystal structure and surface composition of the MOs are obtained by X-ray diffraction patterns, energy dispersive analysis and X-ray photoelectron spectroscopy, respectively. The surface morphology is confirmed from the scanning electron microscopy surface photo-images. The surface area and pore size distribution are studied by the N2 adsorption method. As a proof-of-concept demonstration for the application, ZnO nanoplate structures are envisaged in DSSCs as photoanodes, which enables us to obtain excellent photovoltaic properties with a power conversion efficiency of 5%. The proposed method does not require a sophisticated instrumental setup or harsh conditions, and the method is easily scalable. Hence, it can be applied for the cost-effective and large-scale production of MO nanoparticles with high crystallinity.

An increase in charge collection efficiency and charge mobility from 78 to 89% and 0.02 to 0.04 cm2 V−1 s−1, respectively, in low-temperature solution-processed Zn-doped SnO2 photoanodes resulted in a two-fold enhancement in power conversion efficiency (PCE) as compared to Zn free SnO2 photoanodes in dye-sensitized solar cells (DSSCs).

Employing newly synthesized di-substituted tri-phenyl amine (HMP-9) and carbazole (HMP-11) dyes (with limited acidic carboxyl anchor groups), a power conversion efficiency as high as 7.03% in ZnO nanocrystallite (NC)-based dye-sensitized solar cells (DSSCs) is achieved. The specific molecular designs of HMP-09 and HMP-11 consisting of with and without hexyloxy spacer groups, and added tri-phenyl amine or 9-phenyl-9H-carbazole donor groups, respectively, attached on the ancillary ligands are advantageous, evidenced from electrochemical impedance spectroscopy measurements, for ZnO NC-based DSSCs.

We report for the first time, a high performance photovoltaic cell utilizing earth abundant absorber SnSe, fabricated in thin film form by electrodeposition technique. A solid state device fabricated using CdS as window layer exhibited 0.8% efficiency while using a polysulfide electrolyte in presence of platinum counter electrode exhibited 1.4% solar to electric power conversion efficiency.

Indium oxide (In2O3) is an important wide band-gap semiconductor having applications in a variety of optoelectronic devices. We report here on the low temperature solution deposition of In(OH)3 and In(SO4)(OH)·H2O architectures with various shapes such as cubes, maize corns and giant crystals. The In2O3 nanostructures are then obtained by solid state transformation of In(OH)3 and In(SO4)(OH)·H2O architectures. Shape control is achieved by controlling the local concentration of In3+ ions available for reaction by applying the principles of coordination chemistry, thereby obviating the need of any shape controlling agents. The phase and surface composition is obtained by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. The XPS is used to probe the defect structure of In2O3 architecture. Optical properties of the films, studied by UV-Vis absorption and photoluminescence (PL) spectroscopy measurements, show that the different morphologies have different band-gaps. Furthermore current–voltage characteristics of In2O3–CdSe photoelectrochemical cells are studied, which show that cube–CdSe samples display excellent photovoltaic behaviour, exhibiting a short circuit current density in excess of 10 mA cm−2. The charge transport properties of the In2O3–CdSe photoanodes are studied by impedance spectroscopy, which shows that cube–CdSe samples have lowest resistance to charge transfer.

We demonstrate meticulous fabrication of p-Cu2S/n-CdS heterojunction thin films using a facile wet-chemical approach. Ion exchange of Cu+ with Cd2+ is a serious problem during preparation of Cu2S/CdS multilayered thin films. This issue was addressed by employing polyelectrolyte multilayers on the CdS surface, which completely prevented CdS corrosion, thereby allowing fabrication of heterostructured Cu2S/CdS films. The formation of polyelectrolyte multilayers is monitored using cyclic voltammetry. The heterostructured films are characterized by structure and morphology. We further employed these films as modified p-channel, p-Cu2S/n-CdS thin-film phototransistors, where n-CdS acts as the electron transporting and hole-blocking layer that extracts and grounds the photogenerated electrons. This device exhibited a significant increase in photocurrent density (>75 times), drift mobility (>87 times), and good linearity without having to apply gate voltage, when compared to its individual component device.

A competitive power conversion efficiency of 7.01% is achieved for TiO2-based dye-sensitized solar cells (DSSCs) using a chemically stable and mechanically robust molybdenum di-sulfide (MoS2) counter electrode, synthesized using a simple, scalable and low-temperature wet-chemical process, owing to its good redox reaction stability.

In the present study, a thin layer of Cu-based metal–organic frameworks (MOFs, copper(II) benzene-1,3,5-tricarboxylate) is fabricated using a layer-by-layer technique, and the layer is investigated as a light-absorbing layer in TiO2-based solar cells. Iodine doping of the MOFs is performed to improve the conductivity and charge-transfer reaction across the TiO2/MOF/electrolyte interface. The HOMO and LUMO energy states of the MOF films are estimated to be −5.37 and −3.82 eV (vs vacuum), respectively, which show a well-matched energy cascade with TiO2. For the first time, a TiO2-based solar cell is fabricated successfully using iodine-doped Cu-MOFs as an active layer, demonstrating a cell performance with Jsc = 1.25 mA cm–2 and Eff = 0.26% under illumination of 1 sun radiation. In contrast, the cell with an undoped MOF layer exhibited Jsc = 0.05 mA cm–2 and Eff = 0.008%. Electrochemical impedance spectroscopy of the cells suggests that iodine doping significantly reduces the charge-transfer resistance.

Liquefied petroleum gas (LPG) sensors of hematite nanostructures viz. nanoparticles, nanoparticle-chains and nanorods, chemically synthesized from iron nitrate, sulfate and chloride precursors, respectively, in presence of urea as pH regulating agent are explored. These nanostructures were examined for their structures and morphologies. The Hematite morphology has an impact on crystal structure, Raman shift and charge transfer resistance value. On the basis of results presented herein, we proposed an importance of hematite nanostructures as a sensing material for the LPG sensors. Superior LPG sensor sensitivity of nanoparticles-chains (77.89%) over nanoparticles (68%) and nanorods (58.80%) at 1000 ppm LPG gas levels are imply that the hematite nanostructure (surface area) plays an important role in mediating charge transfer reaction.

Three dicarboxylic acids with different molecular lengths were used as organic linkers to manipulate pore size and surface area of the cobalt based metal–organic-frameworks (MOFs). The pore size and BET surface area of the MOFs were determined and the influence of pore size and surface area on the supercapacitive performance of the MOFs was studied using cyclic voltammetry and chronopotentiometry. Among three MOFs investigated in the present study, the MOF with longer organic linker had larger pores, larger surface area and the MOF film at the electrode surface had a continuously interconnected leaflet like microstructure with less number of structural interfaces which provide the free path for charge transfer. This MOF electrode exhibited highest supercapacitive properties with 179.2 F g −1 , 31.4 Wh kg −1 , and 5.64 kW kg −1 of specific capacitance, energy density and power density, respectively.

In situ growth of upright-standing SnO2 nanoplates connected to horizontally pointed TiO2 nanoneedles to form a new, high surface area hierarchical nanostructure is proposed for the first time and envisaged in ammonia and liquid petroleum gas sensors. The increased surface area due to a hierarchical nanostructure accounts for enhanced gas sensitivity.

We report on fabrication of upright-standing SnO2 nanowalls aligned on FTO substrates by a facile wet chemical method at low temperature. These nanowalls are dual-photosensitized with CdS quantum dots and Z907 dye molecules in order to construct panchromatic dye-sensitized solar cells. We demonstrate that thin CdS quantum dot layer not only acts as a blocking layer preventing recombination of charge carriers, but also contributes as a light absorber. A 158% improvement in power conversion efficiency is observed, which is attributed to improved light absorption, reduced recombination and improved charge collection in presence of CdS quantum dot interlayer.

International audience; Forests of trimetallic nanodendrites composed of Pt, Au, and Ag have been synthesized and their catalytic performances with regard to the methanol oxidation reaction (MOR) were evaluated. Analysis based on elemental mapping revealed homogeneous incorporation of Pt, Au, and Ag throughout the nanodendrite and single crystalline structure. These materials proved active for MOR, with improved electrocatalytic performances with regards to Pt in terms of both overpotential and stability.

Herein, we reports synthesis, characterization and photocatalytic degradation of Rhodamine B under natural sunlight using zinc oxide and Ag-ZnO composite. Zinc oxide nanoparticles were prepared by simple wet chemical method using ethanol-water mixture. Ag-ZnO composite was prepared in two steps by dispersing synthesized ZnO in silver nitrate solution and subsequently reducing it with Ocimum tenuiflorum leaves extract as bioreducing agent. The synthesized bare zinc oxide and Ag-ZnO composite was characterized by various techniques like XRD, DRS, FE-SEM, TEM, SAED, PSD, Zeta potentials, etc. Zinc oxide being wide band gap material can absorbs UV light from solar spectrum which is only 5% so is not efficient material for dye degradation under sunlight. The absorption of visible light was increased by preparing the Ag-ZnO composite. The enhancement in photocatalytic activities of Ag-ZnO composite was observed than bare ZnO. This enhancement is due to shift of absorption edge of ZnO in visible region and decrease in band gap.

A novel architecture of SnO(2) nanowall-arrays coated with rutile-TiO(2) nanoneedles is fabricated for the first time and envisaged in dye-sensitized solar cells. Devices constructed using these architectures showed a power conversion efficiency of 4.12%, which is the highest among the SnO(2) nanostructures grown on conducting substrates by wet chemical methods.

The present work demonstrates a facile, low cost and environmentally friendly technique for carburization of TiO2 nanotubes. XRD and XPS investigations suggest that the anodically grown self-organized TiO2 nanotubes when annealed in an argon filled steel nut–bolt cavity working as an autogenic pressure reactor undergo carburization at 650 °C, which converts TiO2 into TiOyCz. TEM-SAED suggests that the carburized nanotubes are polycrystalline, and also contain some reduced oxides of titanium. The conductivity measurement of the carburized nanotubes shows their conductivity to be close to metals. The electrochemical investigation of the carburized nanotubes demonstrates that the material can be used as a conductive electrode material for electrochemical reactions.

In the present work, thin films of ruthenium based metal–organic frameworks are synthesized using a layer-by-layer (LbL) technique and the film is characterized using XRD, FE-SEM, UV/visible spectroscopy, cyclic voltammetry and photoluminance spectroscopy. Further, the feasibility of the MOF film as a sensitizer in a solar cell is investigated. The HOMO–LUMO level of the frameworks is estimated and is found to be suitable to allow the use of the frameworks as a sensitizer for TiO2. When TiO2 mesoporous film is sensitized with the LBL thin film of the frameworks and a Gratzel type liquid junction solar cell is constructed, it demonstrates the cell performance of Isc = 2.56 mA cm−2, Voc = 0.63 V, FF = 0.63, and Eff = 1.22%. Photoluminescence spectroscopy and electrochemical impedance spectroscopy show that iodine doping into the frameworks is essential to facilitate the photogenerated electron transfer from the frameworks to TiO2.

We report on the synthesis of CdO–CdSe nanoporous architectures from porous CdO architectures by a controlled solution anion exchange method. Monolithic CdCO3 micron sized crystals synthesized in the first step were decomposed by calcination to evolve CO2 to form porous CdO crystals, having a similar outer shape but with a tailored internal nanostructure. Controlled Se2− ion exchange with CdO crystals yielded CdO–CdSe architectures with tunable composition and optoelectronic properties. Pearson's acid–base concept is used as a guiding principle for controlling the morphology and composition of the formed architectures. The photoelectrochemical properties of the system comprising CdO–CdSe architectures were investigated at various stages of ion exchange intervals. CdO–CdSe architectures on indium tin oxide (ITO) is a promising photoelectrode with excellent photovoltaic properties exhibiting a short-circuit current density of 7.36 mA cm−2 under 1 Sun illumination.

Photoelectrochemical cells (PECs) of ZnO/CdSe decorated with a charge separating SnO2 nanoparticles (NPs) layer of various thicknesses are prepared and characterized by using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), UV-visible absorption, energy dispersive X-ray analysis spectroscopy (EDX) and incident photon-to-current conversion efficiency (IPCE) measurements. A uniform coverage of the SnO2 NPs layer over ZnO/CdSe electrode surface is evidenced. The EDX elemental mapping analysis of the ZnO/CdSe/SnO2 PECs demonstrates the presence of Sn and O over the surface. A remarkable improvement in the light harvesting efficiency confirmed from the IPCE measurement, supports an enhancement in current density in the current density-voltage measurement due to increased electron transport and smaller charge recombination. Moreover, these observations are corroborated with the EIS measurement as a cell with SnO2 reveals a reduced charge transfer resistance due to which the power conversion efficiency is increased from 2.20 to 3.41% i.e. 55% compared to the pristine ZnO/CdSe PEC.

Self-organized nanoporous tin oxide films were fabricated by anodizing a tin substrate in an aqueous electrolyte containing oxalic or phosphoric acid. The films were characterized using FE-SEM, XRD, XPS, and TGA. In addition, the supercapacitive properties of the porous oxide films were measured using cyclic voltammetry and galvanostatic charge/discharge technique. The film demonstrated a maximum specific capacitance of 274 F g−1 with long life in electrochemical charge/discharge cycles.

Highly reproducible, wet-chemically processed, CdS buffer-layer free ZnO-CdSe photoelectrochemical cells with 3.38% power conversion efficiency have been fabricated. An enhanced current density is observed due to increase in number of injected photoelectrons with CdSe nanoparticles loading time. Impedance spectroscopy results suggest that interfacial resistance is strongly dependant on CdSe nanoparticles loading time.

We report a coordination chemistry approach for shape-controlled synthesis of α-Fe2O3 (hematite) nanostructures. Three distinct morphologies viz. nanoparticles, nanoparticle-chains and nanorods were synthesized from inorganic iron precursor sources of nitrate, sulfate and chloride, respectively, in the presence of urea as a pH regulating agent and were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The responsible growth mechanism and possible factors controlling the morphologies are explored. Photoelectrochemical cells constructed by utilizing these nanostructures produced stable photocurrents in iodide electrolyte. The nanoparticle-chains morphology of α-Fe2O3 revealed the highest photocurrent density of 0.36 mA cm−2 at 0 V bias conditions under 1 Sun illumination. The reason for the high performance is investigated with the help of impedance spectroscopy analysis, wherein the electrode composed of nanoparticle-chains affords the lowest charge transfer resistance and thereby the highest photoconversion yield, as compared to those of the nanoparticle and nanorod electrodes.

The development of earth-abundant electrocatalysts (ECs) operating at high current densities in water splitting electrolyzers is pivotal for the widespread use of the current green hydrogen production plants. Transition metal dichalcogenides (TMDs) have emerged as promising alternatives to the most efficient noble metal ECs, leading to a wealth of research. Some strategies based on material nanostructuring and hybridization, introduction of defects and chemical/physical modifications appeared as universal approaches to provide catalytic properties to TMDs, regardless of the specific material. In this work, we show that even a theoretically poorly catalytic (and poorly studied) TMD, namely zirconium diselenide (ZrSe2), can act as an efficient EC for the hydrogen evolution reaction (HER) when exfoliated in the form of two-dimensional (2D) few-layer flakes. We critically show the difficulties of explaining the catalytic mechanisms of the resulting ECs in the presence of complex structural and chemical modifications, which are nevertheless evaluated extensively. By doing so, we also highlightthe easiness of transforming 2D TMDs into effective HER-ECs. To strengthen our message in practical environments, we report ZrSe2-based acidic (proton exchange membrane [PEM]) and alkaline water electrolyzers operating at 400mA cm–2at a voltage of 1.88 and 1.92 V, respectively, thus competing with commercial technologies.

The engineering of the structural and morphological properties of nanomaterials is a fundamental aspect to attain desired performance in energy storage/conversion systems and multifunctional composites. We report the synthesis of room temperature-stable metallic rutile VO2 (VO2 (R)) nanosheets by topochemically transforming liquid-phase exfoliated VSe2 in a reductive Ar-H2 atmosphere. The asproduced VO2 (R) represents an example of two-dimensional (2D) nonlayered materials, whose bulk counterparts do not have a layered structure composed by layers held together by van der Waals force or electrostatic forces between charged layers and counterbalancing ions amid them. By pretreating the VSe2 nanosheets by O-2 plasma, the resulting 2D VO2 (R) nanosheets exhibit a porous morphology that increases the material specific surface area while introducing defective sites. The assynthesized porous (holey)-VO2 (R) nanosheets are investigated as metallic catalysts for the water splitting reactions in both acidic and alkaline media, reaching a maximum mass activity of 972.3 A g(-1) at -0.300 V vs RHE for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 (faradaic efficiency = 100%, overpotential for the HER at 10 mA cm(-2) = 0.184 V) and a mass activity (calculated for a non 100% faradaic efficiency) of 745.9 A g(-1) at +1.580 V vs RHE for the oxygen evolution reaction (OER) in 1 M KOH (overpotential for the OER at 10 mA cm(-2) = 0.209 V). By demonstrating proof-of-concept electrolyzers, our results show the possibility to synthesize special material phases through topochemical conversion of 2D materials for advanced energy-related applications.