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Oxygen vacancy defects are highly desirable for photoelectrochemical water splitting reactions of TiO2 nanomaterials because they act as electron donors and thereby enhance the electrical conductivity and charge transport property of TiO2. For TiO2 nanowires reported to date, oxygen vacancies are mainly generated by post-treatment of the as-synthesized nanowires. This comes with a disadvantage that oxygen vacancies are found to form just within a few tens of nanometers at the outer surface of these nanowires, and the photocurrent density is significantly reduced by two to three orders of magnitude when ultraviolet light is filtered out from the AM 1.5G light. Here, we demonstrate, for the first time, the controlled growth of 1D TiO2 nanostructures with different morphologies and with incorporation of oxygen vacancy defects on a Si substrate by a single-step, catalyst-assisted pulsed laser deposition (PLD) method. Photoelectrochemical water splitting measurements under simulated sunlight show that the decorated nanowires exhibit one of the highest photoactivity values in the visible region (>430 nm) reported to date, which represents 87% of the overall photocurrent. The higher activity in the visible region can be attributed to more conductive TiO2 nanostructures (i.e., with a larger amount of oxygen vacancy defects), and the enhanced charge transfer from the nanocrystallites to the core of the decorated nanowires.

Electrodeposited Au–Pt alloy nanoparticles supported on ITO-glass substrates have been used as a model catalyst to study the electro-oxidation of methanol (0.5 M) in a KOH (0.5 M) electrolyte. Using cyclic voltammetry, we show that the Au–Pt alloy nanoparticles exhibit a significantly higher catalytic activity than the Pt nanoparticles, while the Au nanoparticles show no catalytic affinity toward electro-oxidation of methanol. The Au–Pt alloy nanoparticles are also found to be catalytically more reactive than bimetallic Au-core Pt-shell and Pt-core Au-shell nanoparticles. We further show that these Au–Pt alloy nanoparticles working in alkaline solution could act as an amperometric sensor for the determination of alcohol concentration. The exceptional performance of this nanoalloy sensor, including its short response time (2 s), relatively large linear range (1–11 mM), low detection limit (0.1 mM), high sensitivity (0.043 mA cm−2 mM−1) and long-term stability (over 90 days), are also characterized. The present nanoalloy sensor also has the lowest working potential (0.25 V), making it less prone to an interference effect.