Au-decorated 3D/1D titanium dioxide flower-like/rod bilayers for photoelectrochemical water oxidation

Photoelectrochemical water splitting can be regarded as a promising technology for renewable hydrogen production. In the current work, a facile hydrothermal synthesis method was used to directly grow TiO2 flower-like structures/TiO2 nanorods on a conductive glass substrate. Moreover, three different gold deposition methods, namely, a photoreduction method (PR), the Turkevich method (TK) and a combination of both methods (CM), were applied to decorate the formed flower-like structures with gold nanoparticles (GNPs). The type of deposition technique affected the size, size distribution, loading, surface coverage and shape of the obtained GNPs. With the PR technique, the photocurrent increased 3.5-fold compared to that of the bare flower-like structures. With the TK method, a narrow GNP distribution was obtained, yielding a 6.15-fold increase in photocurrent. Using the CM approach, a 1.21-, 26.86- and 12.79-fold increase was observed for current density compared to that of the corresponding bare samples. All samples showed stable chronoamperometric performance under illumination without any signs of photocorrosion or performance deterioration. Electrochemical impedance spectroscopy showed that the CM approach decreased the semiconductor/electrolyte interfacial resistance to 37, 2.5 and 3.1% of the values for the bare samples. Bode phase plots showed that the stacked flower-like structures can be considered electron-hole recombination centres, leading to an observable broadening of the maximum-frequency peak.