Mechanistic understanding of the thermal-assisted photocatalytic oxidation of methanol-to-formaldehyde with water vapor over Pt/SrTiO.

Anaerobic thermal-assisted photocatalytic methanol conversion in the gas phase in the presence of water vapor has been suggested as an interesting way to generate formaldehyde as a valuable coupled product in addition to H production. Here, the reaction mechanism and photocatalyst deactivation are investigated in detail using diffuse reflectance infrared fourier transform (DRIFTS) and electron paramagnetic resonance (EPR) spectroscopy. EPR shows that paramagnetic oxygen vacancies are not involved in the reaction mechanism over undoped SrTiO.

Nanometer-Resolved Operando Photo-Response of Faceted BiVO Semiconductor Nanoparticles.

Photo(electro)catalysis with semiconducting nanoparticles (NPs) is an attractive approach to convert abundant but intermittent renewable electricity into stable chemical fuels. However, our understanding of the microscopic processes governing the performance of the materials has been hampered by the lack of operando characterization techniques with sufficient lateral resolution. Here, we demonstrate that the local surface potentials of NPs of bismuth vanadate (BiVO) and their response to illumination differ between adjacent facets and depend strongly on the pH of the ambient electrolyte.

A high-purity gas-solid photoreactor for reliable and reproducible photocatalytic CO reduction measurements.

Reactions between a gas phase and a solid material are of high importance in the study of alternative ways for energy conversion utilizing otherwise useless carbon dioxide (CO). The photocatalytic CO reduction to hydrocarbon fuels like e.g.

Electrochemical decarboxylation of acetic acid on boron-doped diamond and platinum-functionalised electrodes for pyrolysis-oil treatment.

Electrochemical decarboxylation of acetic acid on boron-doped-diamond (BDD) electrodes was studied as a possible means to decrease the acidity of pyrolysis oil. It is shown that decarboxylation occurs without the competitive oxygen evolution reaction (OER) on BDD electrodes to form methanol and methyl acetate by consecutive reaction of hydroxyl radicals with acetic acid. The performance is little affected by the applied current density (and associated potential), concentration, and the pH of the solution.

Carbon monoxide separation: past, present and future.

Large amounts of carbon monoxide are produced by industrial processes such as biomass gasification and steel manufacturing. The CO present in vent streams is often burnt, this produces a large amount of CO, , oxidation of CO from metallurgic flue gasses is solely responsible for 2.7% of manmade CO emissions.

Design and validation of a low-cost open-source impedance based quartz crystal microbalance for electrochemical research.

The quartz crystal microbalance (QCM) measurement technique is utilized in a broad variety of scientific fields and applications, where surface and interfacial processes are relevant. However, the costs of purchasing QCMs is typically high, which has limited its employment in education as well as by scientists in developing countries. In this article, we present an open-source QCM, built on the OpenQCM project, and using an impedance-based measurement technique (QCM-I), which can be built for <200 euro.

Photocatalytic nanocomposite membranes for environmental remediation.

We report the design and one-pot synthesis of Ag-doped BiVOembedded in reduced graphene oxide (BiVO:Ag/rGO) nanocomposites via a hydrothermal processing route. The binary heterojunction photocatalysts exhibited high efficiency for visible light degradation of model dyes and were correspondingly used for the preparation of photocatalytic membranes using polyvinylidene fluoride (PVDF) or polyethylene glycol (PEG)-modified polyimide (PI), respectively. The surface and cross-section images combined with elemental mapping illustrated the effective distribution of the nanocomposites within the polymeric membranes.

Facet-Dependent Surface Charge and Hydration of Semiconducting Nanoparticles at Variable pH.

Understanding structure and function of solid-liquid interfaces is essential for the development of nanomaterials for various applications including heterogeneous catalysis in liquid phase processes and water splitting for storage of renewable electricity. The characteristic anisotropy of crystalline nanoparticles is believed to be essential for their performance but remains poorly understood and difficult to characterize. Dual scale atomic force microscopy is used to measure electrostatic and hydration forces of faceted semiconducting SrTiO nanoparticles in aqueous electrolyte at variable pH.

CrO-Mediated Performance Enhancement of Ni/NiO-Mg:SrTiO in Photocatalytic Water Splitting.

By photodeposition of CrO on SrTiO-based semiconductors doped with aliovalent Mg(II) and functionalized with Ni/NiO catalytic nanoparticles (economically significantly more viable than commonly used Rh catalysts), an increase in apparent quantum yield (AQYs) from ∼10 to 26% in overall water splitting was obtained. More importantly, deposition of CrO also significantly enhances the stability of Ni/NiO nanoparticles in the production of hydrogen, allowing sustained operation, even in intermittent cycles of illumination. elemental analysis of the water constituents during or after photocatalysis by inductively coupled plasma mass spectrometry/optical emission spectrometry shows that after CrO deposition, dissolution of Ni ions from Ni/NiO-Mg:SrTiO is significantly suppressed, in agreement with the stabilizing effect observed, when both Mg dopant and CrO are present.

Synergy of ferroelectric polarization and oxygen vacancy to promote CO photoreduction.

Solar-light driven CO reduction into value-added chemicals and fuels emerges as a significant approach for CO conversion. However, inefficient electron-hole separation and the complex multi-electrons transfer processes hamper the efficiency of CO photoreduction. Herein, we prepare ferroelectric BiTiNbO nanosheets and employ corona poling to strengthen their ferroelectric polarization to facilitate the bulk charge separation within BiTiNbO nanosheets.

Electrochemically Induced pH Change: Time-Resolved Confocal Fluorescence Microscopy Measurements and Comparison with Numerical Model.

Confocal fluorescence microscopy is a proven technique, which can image near-electrode pH changes. For a complete understanding of electrode processes, time-resolved measurements are required, which have not been achieved previously. Here we present the first measurements of time-resolved pH profiles with confocal fluorescence microscopy.

Photocatalytic Oxidation of Propane Using Hydrothermally Prepared Anatase-Brookite-Rutile TiO Samples. An In Situ DRIFTS Study.

Photocatalytic oxidation of propane using hydrothermally synthesized TiO samples with similar primary crystal size containing different ratios of anatase, brookite and rutile phases has been studied by measuring light-induced propane conversion and in situ DRIFTS (diffuse reflectance Fourier transform infrared spectroscopy). Propane was found to adsorb on the photocatalysts, both in the absence and presence of light. The extent of adsorption depends on the phase composition of synthesized titania powders and, in general, it decreases with increasing rutile and brookite content.

Comparative Analysis of Photocatalytic and Electrochemical Degradation of 4-Ethylphenol in Saline Conditions.

We evaluated electrochemical degradation (ECD) and photocatalytic degradation (PCD) technologies for saline water purification, with a focus on rate comparison and formation and degradation of chlorinated aromatic intermediates using the same non-chlorinated parent compound, 4-ethylphenol (4EP). At 15 mA·cm, and in the absence of chloride (0.6 mol·L NaNO was used as supporting electrolyte), ECD resulted in an apparent zero-order rate of 30 μmol L·h, whereas rates of ∼300 μmol L·h and ∼3750 μmol L·h were computed for low (0.

Integration of Molybdenum-Doped, Hydrogen-Annealed BiVO with Silicon Microwires for Photoelectrochemical Applications.

H-BiVO :Mo was successfully deposited on microwire-structured silicon substrates, using indium tin oxide (ITO) as an interlayer and BiOI prepared by electrodeposition as precursor. Electrodeposition of BiOI, induced by the electrochemical reduction of -benzoquinone, appeared to proceed through three stages, being nucleation of particles at the base and bottom of the microwire arrays, followed by rapid (homogeneous) growth, and termination by increasing interfacial resistances. Variations in charge density and morphology as a function of spacing of the microwires are explained by (a) variations in mass transfer limitations, most likely associated with the electrochemical reduction of -benzoquinone, and (b) inhomogeneity in ITO deposition.

Driving Surface Redox Reactions in Heterogeneous Photocatalysis: The Active State of Illuminated Semiconductor-Supported Nanoparticles during Overall Water-Splitting.

Materials used for photocatalytic overall water splitting (POWS) are typically composed of light-absorbing semiconductor crystals, functionalized with so-called cocatalytic nanoparticles to improve the kinetics of the hydrogen and/or oxygen evolution reactions. While function, quantity, and protection of such metal(oxide) nanoparticles have been addressed in the literature of photocatalysis, the stability and transients in the active oxidation-state upon illumination have received relatively little attention. In this Perspective, the latest insights in the active state of frequently applied cocatalysts systems, including Pt, Rh/CrO, or Ni/NiO , will be presented.

Promoting Photocatalytic Overall Water Splitting by Controlled Magnesium Incorporation in SrTiO Photocatalysts.

SrTiO is a well-known photocatalyst inducing overall water splitting when exposed to UV irradiation of wavelengths <370 nm. However, the apparent quantum efficiency of SrTiO is typically low, even when functionalized with nanoparticles of Pt or Ni@NiO. Here, we introduce a simple solid-state preparation method to control the incorporation of magnesium into the perovskite structure of SrTiO .

Overcoming the Instability of Nanoparticle-Based Catalyst Films in Alkaline Electrolyzers by using Self-Assembling and Self-Healing Films.

Engineering stable electrodes using highly active catalyst nanopowders for electrochemical water splitting remains a challenge. We report an innovative and general approach for attaining highly stable catalyst films with self-healing capability based on the in situ self-assembly of catalyst particles during electrolysis. The catalyst particles are added to the electrolyte forming a suspension that is pumped through the electrolyzer.

Transient Behavior of Ni@NiO Functionalized SrTiO in Overall Water Splitting.

Transients in the composition of Ni@NiO core-shell co-catalysts deposited on SrTiO are discussed on the basis of state-of-the-art continuous analysis of photocatalytic water splitting, and post-XPS and TEM analyses. The formation of excessive hydrogen (H:O ≫ 2) in the initial stages of illumination demonstrates oxidation of Ni(OH) to NiOOH (nickel oxyhydroxide), with the latter catalyzing water oxidation. A disproportionation reaction of Ni and NiOOH, yielding Ni(OH) with residual embedded Ni, occurs when illumination is discontinued, which explains repetitive transients in (excess) hydrogen and oxygen formation when illumination is reinitiated.

Solid Electrolyte Interphase (SEI) at TiO Electrodes in Li-Ion Batteries: Defining Apparent and Effective SEI Based on Evidence from X-ray Photoemission Spectroscopy and Scanning Electrochemical Microscopy.

The high (de)lithiation potential of TiO (ca. 1.7 V vs Li/Li in 1 M Li) decreases the voltage and, thus, the energy density of a corresponding Li-ion battery.

Tailoring Mixed-Halide, Wide-Gap Perovskites via Multistep Conversion Process.

Wide-band-gap mixed-halide CH3NH3PbI3-XBrX-based solar cells have been prepared by means of a sequential spin-coating process. The spin-rate for PbI2 as well as its repetitive deposition are important in determining the cross-sectional shape and surface morphology of perovskite, and, consequently, J-V performance. A perovskite solar cell converted from PbI2 with a dense bottom layer and porous top layer achieved higher device performance than those of analogue cells with a dense PbI2 top layer.

Iron-Treated NiO as a Highly Transparent p-Type Protection Layer for Efficient Si-Based Photoanodes.

Sputter deposition of 50 nm thick NiO films on p(+)-n-Si and subsequent treatment in an Fe-containing electrolyte yielded highly transparent photoanodes capable of water oxidation (OER) in alkaline media (1 M KOH) with high efficiency and stability. The Fe treatment of NiO thin films enabled Si-based photoanode assemblies to obtain a current density of 10 mA/cm(2) (requirement for >10% efficient devices) at 1.15 V versus RHE (reversible hydrogen electrode) under red-light (38.

Protection of p(+)-n-Si Photoanodes by Sputter-Deposited Ir/IrOx Thin Films.

Sputter deposition of Ir/IrOx on p(+)-n-Si without interfacial corrosion protection layers yielded photoanodes capable of efficient water oxidation (OER) in acidic media (1 M H2SO4). Stability of at least 18 h was shown by chronoamperomety at 1.23 V versus RHE (reversible hydrogen electrode) under 38.

Photodeposition of copper and chromia on gallium oxide: the role of co-catalysts in photocatalytic water splitting.

Split second: The photocatalytic activity of gallium oxide (β-Ga2 O3) depends strongly on the co-catalysts CuOx and chromia, which can be efficiently deposited in a stepwise manner by photoreduction of Cu(2+) and CrO4 (2-). The water-splitting activity can be tuned by varying the Cu loading in the range 0.025-1.

Surface-Modified TiO Photocatalysts Prepared by a Photosynthetic Route: Mechanism, Enhancement, and Limits.

Surface-modified TiO photocatalysts were synthesized by a photosynthetic route involving visible-light-induced (λ>455 nm) activation of benzene and toluene at the surface of TiO leading to the formation of carbonaceous polymeric deposits. IR spectroscopic and photoelectrochemical experiments showed that the mechanism of the photosynthetic reactions involves intra-bandgap surface states at TiO related to surface OH groups interacting with adsorbed aromatic molecules. The photosynthesized surface-modified TiO materials exhibited enhanced activity, relative to pristine TiO , in photocatalytic degradation (and complete mineralization) of 4-chlorophenol.