Modulating the interaction between gold and TiO2 nanowires for enhanced solar driven photoelectrocatalytic hydrogen generation

Abstract

The interaction strength of Au nanoparticles with pristine and nitrogen doped TiO₂ nanowire surfaces was analysed using density functional theory and their significance in enhancing the solar driven photoelectrocatalytic properties was elucidated. In this article, we prepared 4-dimethylaminopyridine capped Au nanoparticle decorated TiO₂ nanowire systems. The density functional theory calculations show {101} facets of TiO₂ as the preferred phase for dimethylaminopyridine–Au nanoparticles anchoring with a binding energy of −8.282 kcal mol⁻¹. Besides, the interaction strength of Au nanoparticles was enhanced nearly four-fold (−35.559 kcal mol⁻¹) at {101} facets via nitrogen doping, which indeed amplified the Au nanoparticle density on nitrided TiO₂. The Au coated nitrogen doped TiO₂ (N–TiO₂–Au) hybrid electrodes show higher absorbance owing to the light scattering effect of Au nanoparticles. In addition, N–TiO₂–Au hybrid electrodes block the charge leakage from the electrode to the electrolyte and thus reduce the charge recombination at the electrode/electrolyte interface. Despite the beneficial band narrowing effect of nitrogen in TiO₂ on the electrochemical and visible light activity in N–TiO₂–Au hybrid electrodes, it results in low photocurrent generation at higher Au NP loading (3.4 × 10⁻⁷ M) due to light blocking the N–TiO₂ surface. Strikingly, even with a ten-fold lower Au NP loading (0.34 × 10⁻⁷ M), the synergistic effects of nitrogen doping and Au NPs on the N–TiO₂–Au hybrid system yield high photocurrent compared to TiO₂ and TiO₂–Au electrodes. As a result, the N–TiO₂–Au electrode produces nearly 270 μmol h⁻¹ cm⁻² hydrogen, which is nearly two-fold higher than the pristine TiO₂ counterpart. The implications of these findings for the design of efficient hybrid photoelectrocatalytic electrodes are discussed.