Novel NiWO₄ and CoWO₄ nanostructures showed excellent electrochemical properties for supercapacitor electrodes, better than those previously reported for these materials.

It has been more than 40 years since Fujishima and Honda demonstrated water splitting using TiO₂, yet there is still no clear mechanism by which surface holes on TiO₂ oxidize water. In this paper, we use a range of complementary techniques to study this reaction that provide a unique insight into the reaction mechanism. Using transient photocurrent and transient absorption spectroscopy, we measure both the kinetics of electron extraction (t_50% ≈ 200 μs, 1.5V_RHE) and the kinetics of hole oxidation of water (t_50% ≈ 100 ms, 1.5V_RHE) as a function of applied potential, demonstrating the water oxidation by TiO₂ holes is the kinetic bottleneck in this water-splitting system. Photoinduced absorption spectroscopy measurements under 5 s LED irradiation are used to monitor the accumulation of surface TiO₂ holes under conditions of photoelectrochemical water oxidation. Under these conditions, we find that the surface density of these holes increases nonlinearly with photocurrent density. In alkali (pH 13.6), this corresponded to a rate law for water oxidation that is third order with respect to surface hole density, with a rate constant k_WO = 22 ± 2 nm⁴·s^–1. Under neutral (pH = 6.7) and acidic (pH = 0.6) conditions, the rate law was second order with respect to surface hole density, indicative of a change in reaction mechanism. Although a change in reaction order was observed, the rate of reaction did not change significantly over the wide pH range examined (with TOFs per surface hole in the region of 20–25 s^–1 at ∼1 sun irradiance). This showed that the rate-limiting step does not involve OH^– nucleophilic attack and demonstrated the versatility of TiO₂ as an active water oxidation photocatalyst over a wide range of pH.

We report a systematic study into the importance of carrier solvent on the Aerosol-Assisted Chemical Vapour Deposition (AACVD) of fluorine-doped tin oxide (FTO) films. In particular, the resultant effects on both the optical transparency and electrical conductivity properties are reported with optimised films showing figures-of merit significantly beyond commercial products. Depositions were carried out at substrate temperatures of 500, 550 and 600 °C using either N₂ or air as the carrier gas. The carrier solvent was found to have a marked effect on film quality and performance characteristics. Hall Effect results indicate that use of propan-2-ol as carrier solvent and air as carrier gas gave the best performing n-type FTO thin films overall that exhibited high optical transparency (>80% at 550 nm) and resistivity values of 4 × 10⁻⁴ Ω cm, with charge carrier density and carrier mobility values of 4 × 10²⁰ cm⁻³ and 39 cm² V⁻¹ s⁻¹ respectively, in addition to haze values of 10–15%. Such parameters are ideal for thin film solar cell applications and have significantly higher figures of merit compared to current commercial materials. Success of this method of deposition is attributed, in part, to a halide transfer reaction in which part fluorine substitution of the tin precursor occurs in the solvent resulting in a direct tin–fluorine bond. The work shows the key role carrier solvents play in AACVD in directing the system chemistry.

We present a novel approach towards achieving high visible transmittance for vanadium dioxide (VO₂) coated surfaces whilst maintaining the solar energy transmittance modulation required for smart-window applications. Our method deviates from conventional approaches and utilizes subwavelength surface structures, based upon those present on the eyeballs of moths, that are engineered to exhibit broadband, polarization insensitive and wide-angle antireflection properties. The moth-eye functionalised surface is expected to benefit from simultaneous super-hydrophobic properties that enable the window to self-clean. We develop a set of design rules for the moth-eye surface nanostructures and, following this, numerically optimize their dimensions using parameter search algorithms implemented through a series of Finite Difference Time Domain (FDTD) simulations. We select six high-performing cases for presentation, all of which have a periodicity of 130 nm and aspect ratios between 1.9 and 8.8. Based upon our calculations the selected cases modulate the solar energy transmittance by as much as 23.1% whilst maintaining high visible transmittance of up to 70.3%. The performance metrics of the windows presented in this paper are the highest calculated for VO₂ based smart-windows.