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A novel microwave-electrochemical process is shown to allow Fe-Co alloy to be formed at a stainless steel electrode under fast mass transport − high temperature deposition conditions. In contrast to the Fe-Co alloy formed under ambient conditions, the microwave Fe-Co alloy is produced with a Fe:Co ratio close to unity (mass transport controlled deposition). Unusual properties of the new alloy material include good electrocatalytic performance for the hydrogen evolution reaction (HER), showing low onset overpotential (145 mV), high exchange current density (20 mA cm−2) and Tafel parameters close to those for Pt on stainless steel. It is suggested that in future the microwave-electrochemical deposition method can help providing novel sustainable alloy catalyst materials for a wider range of applications.

Sugarcane bagasse ash sand (SBAS) can be used as a bioadditive in concrete. However, little is known about its effects on the steel corrosion process. This paper reports the evaluation of the corrosion susceptibilities of steel immersed in simulate concrete pore solutions, with addition of SBAS, to understand the corrosion process in reinforced structure. The open-circuit potential profiles and polarisation curves suggested the favourable formation of a passive film on the steel immersed in the SBAS-containing medium. Electrochemical impedance spectroscopy confirmed that the SBAS-containing medium presents better passivating properties, showing that this recycled material can be used as corrosion inhibitor for reinforced concrete, encouraging its use in the civil industry.

BiVO4 has been receiving attention for applications in photoelectrochemical devices. This paper describes the effect of different alcohol solvents (ethanol, ethylene-glycol, PEG300 and PEG 400) on the morphology, crystal growth, crystalline size, thickness, photophysical and photoelectrochemical properties of BiVO4 photoanodes prepared from a suitable, simple and inexpensive one-step process. All samples exhibited good crystallinity with the monoclinic phase dominating and with suitable bandgap for visible light harvesting; but the morphology, thickness, and resulting photocurrents varied broadly. The unmodified BiVO4 photoanode prepared with PEG 300, gave a particularly good photocurrent of 0.77 mA cm−2 at 1.23 V vs RHE under illumination of 100 mW cm−2. In this case, a higher value for the ratio between the intensities of the XRD peaks, (040)/(121), was verified, as well as smaller crystallite size. Considering the type of solvent, the BiVO4 photoanode prepared with PEG 300 exhibited a more intense photocurrent. The optimization of the solvent employed in the synthesis of the BiVO4 photoanode is a crucial step in the development of a photoelectrochemical device based on this material.

Alloys and composites that contain molybdenum have been studied due to their excellent properties, such as corrosion resistance and catalytic activity. In this work, the parameters for Cu-Zn-Mo system electrodeposition were studied, such as deposition potentials and concentration of electroactive species. The deposition potentials were examined using cyclic voltammetry and anodic linear stripping voltammetry (ALSV), the deposit morphology was evaluated using scanning electron microscopy (SEM) and crystallographic characterization was carried out for X-ray diffraction (XRD). The voltammetry studies indicated co-deposition of the metals in potentials more negative than -1.2 V, and a potential deposition at -1.5 V was chosen. The coatings presented morphology compact with small agglomerated particles with cauliflower structures, and the content of molybdenum, copper, and zinc ranged from 5 to 8%, 30 to 40% and 20 to 28%, respectively.

Photo-catalytic performance for oxide films, here for inkjet-printed TiO2 (ca. 1 μm thickness on FTO) and for spray-pyrolysis-coated Nb2O5 (ca. 1 μm thickness on FTO), is affected by oxygen vacancies that form during vacuum-heat treatment at 550 °C. The effects of the oxygen vacancies are associated with formation of Ti(III) and Nb(IV) sites, respectively, and therefore optically visible as “grey” coloration. Photo-electrochemical light-on-off transient experiments are performed in the limit of thin film photoanodes, where front and back illumination result in the same photo-current responses (i.e. with negligible effects from internal light absorption gradients). It is shown that generally the magnitude of photo-currents correlates linearly with light intensity, which is indicative of dominant “photo-capacitive” behaviour. At an applied voltage of 0.4 V vs. SCE (in the plateau region of the photo-current responses) the potential and also the pH (going from 1.0 M KOH to 0.1 M HClO4 in the presence of methanol quencher) have no significant effect on photo-currents; that is, surface chemical/kinetic effects appear to be unimportant and interfacial hole transfer may be rate limiting. Under these conditions (and based on a simplistic mechanistic model) changes in photo-currents introduced by oxygen vacancy doping (detrimental for TiO2 and beneficial for Nb2O5) are assigned primarily to changes in electron mobility.

One-step deposition of photoelectrochemically active BiVO4 (monoclinic) from a polyethylene glycol (PEG300) precursor paint onto titanium substrates is demonstrated to lead to more complex multioxide phase films. Photocurrents in 0.5 M Na2SO4 remain relatively low when compared to those reported on tin-doped indium oxide (ITO) substrates, possibly due to the effect of detrimental underlying titanium oxide phases or mixed phases. For comparison, the one-step deposition is demonstrated also for the direct formation of V2O5 nanocrystalline films, which also exhibited low photoelectrochemical activity. Impregnation of nanocrystalline V2O5 with aqueous Bi3+ is shown to cause substantial recrystallization with formation of much more photoactive BiVO4. In particular, on low-temperature (high surface area) nano-V2O5 (400 °C) and after further mild annealing at 400 °C much improved photoelectrochemical water oxidation activity (ca. 0.3 mA cm−2 at 1.0 V vs Ag/AgCl (KCl (3 M) at 0.1-W cm−2 xenon lamp radiation) is observed. This opens up a new mild temperature two-step route for BiVO4 photocatalysts on practical titanium substrates.

Transparent nano-structured hematite (α-Fe2O3) films of approximately 550 nm thickness on tin-doped indium oxide (ITO) have been obtained conveniently by ink-jet printing of a Fe(NO3)3/Brij® O10 precursor ink and subsequent annealing at 500 °C in air. When illuminated with a blue LED (λ = 455 nm, ca. 100 mW cm−2), the hematite films exhibited photocurrents of up to 70 μA cm−2 at 0.4 V vs. SCE in 0.1 M NaOH electrolyte. Thermal annealing in vacuum at 500 °C for 2 h increased photocurrents more than three times to 230 μA cm−2 in agreement with previous literature reports for pure hematite materials. These results suggest that a simple ink-jetting process with surfactants is viable. The effects of vacuum-annealing on the photoelectrical properties of α-Fe2O3 films are discussed in terms of a sub-surface state templating hypothesis based on data gathered from photo-transients, field emission scanning electron microscopy, X-ray photoelectron spectroscopy analysis, X-ray diffraction, photocurrent spectra, and cyclic voltammetry.

In this work, results on the preparation and characterization of ZnSe thin films obtained by electrodeposition are presented. Voltammetric curves were recorded in order to characterize the electrochemical behavior of the Zn(II)+Se(IV) system. Thin films were deposited potentiostatically from an unstirred, deareated aqueous solution onto Au or ITO glass substrates. The deposits morphology and physics properties were characterised by FEG, UV-Vis and DRX.

Polymers of intrinsic microporosity (PIM or here PIM-EA-TB) offer a highly rigid host environment into which hexachloroplatinate(IV) anions are readily adsorbed and vacuum carbonised (at 500 °C) to form active embedded platinum nanoparticles. This process is characterised by electron and optical microscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods, which reveal that the PIM microporosity facilitates the assembly of nanoparticles of typically 1.0 to 2.5-nm diameter. It is demonstrated that the resulting carbonised “Pt@cPIM” from drop-cast films of ca. 550-nm average thickness, when prepared on tin-doped indium oxide (ITO), contain not only fully encapsulated but also fully active platinum nanoparticles in an electrically conducting hetero-carbon host. Alternatively, for thinner films (50–250 nm) prepared by spin coating, the particles become more exposed due to additional loss of the carbon host. In contrast to catalyst materials prepared by vacuum-thermolysed hexachloroplatinate(IV) precursor, the platinum nanoparticles within Pt@cPIM retain high surface area, electrochemical activity and high catalyst efficiency due to the molecular rigidity of the host. Data are presented for oxygen reduction, methanol oxidation and glucose oxidation, and in all cases, the high catalyst surface area is linked to excellent catalyst utilisation. Robust transparent platinum-coated electrodes are obtained with reactivity equivalent to bare platinum but with only 1 μg Pt cm−2 (i.e. ~100% active Pt nanoparticle surface is maintained in the carbonised microporous host). [Figure not available: see fulltext.]