Modulating the interaction between gold and TiO₂nanowires for enhanced solar driven photoelectrocatalytic hydrogen generation

Abstract

The interaction strength of Au nanoparticles with pristine and nitrogen doped TiO 2 nanowire surface 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 nanoparticles decorated TiO 2 nanowires system. The density functional theory calculations show {101}facets of TiO 2 as the preferred phase for dimethylaminopyridine-Au nanoparticles anchoring 10 with a binding energy of -8.282 kcal/mol. Besides, the interaction strength of Au nanoparticles was enhanced nearly four-fold (-35.559 kcal/mol) at {101} facets via nitrogen doping, which indeed amplified the Au nanoparticle density on nitrided TiO 2 . The Au coated nitrogen doped TiO 2 (N-TiO 2 -Au) hybrid electrodes show higher absorbance owing to the light scattering effect of Au nanoparticles. In addition, N-TiO 2 -Au hybrid electrodes block the charge leakage from electrode to electrolyte and thus reduce the 15 charge recombination at electrode/electrolyte interface. Despite the beneficial band narrowing effect of nitrogen in TiO 2 on the electrochemical and visible light activity in N-TiO 2 -Au hybrid electrodes, it results low photocurrent generation at higher Au NPs loading (3.4×10 -7 M) due to light blocking to NTiO 2 surface. Strikingly, even with a ten-fold lower Au NPs loading (0.34×10 -7 M), the synergistic effects of nitrogen doping and Au NPs on N-TiO 2 -Au hybrid system yield high photocurrent compare to TiO 2 20 and TiO 2 -Au electrodes. As a result, N-TiO 2 -Au electrode produces nearly 270 µmol/hr cm -2 hydrogen, which is nearly two-fold higher than the pristine TiO 2 counterpart. The implications of these findings for the design of efficient hybrid photoelectrocatalytic electrodes are discussed.

Why the thin film form of a photocatalyst is better than the particulate form for direct solar-to-hydrogen conversion: a poor man's approach

“…The photocatalysts of powder form were evaluated by following procedures reported in the literature. 2,13 Some of the points derived from the results are worth highlighting: (a) the hydrogen production activities of powder catalysts (P25 and Pd/P25) were low compared to those of the corresponding thin lm form catalysts even though the catalyst remained the same. (b) A small (1 mg) amount of catalyst in powder form provided a large amount of hydrogen, while a large amount of catalyst (25 mg) led to a lower hydrogen yield, indicating a reverse correlation between the content and the rate.…”

“…9 Among these, the solar-driven water splitting reaction with suitable combination of semiconductors and metal nanostructures is preferred as the method is truly renewable. [10][11][12][13] However, H 2 production from the particulate form of photocatalyst is hindered by several limitations. For example, a simple doubling of catalyst quantity from 75 to 150 mg decreases the efficiency from 6.3 to 2.7%, respectively, due to several factors.…”

Current progress in developing metal oxide nanoarrays-based photoanodes for photoelectrochemical water splitting

“…The combination of Au NPs and NRs significantly enhanced light photoactivity in both the UV and visible regions and improved the PEC performance. Until now, Au nanoparticle-modified TiO 2 NW array photoelectrodes have been well reported [282]. In addition, new attempts on other metal nanoparticles have also been studied, such as Ag [283].…”

WO3 nanofibrous backbone scaffolds for enhanced optical absorbance and charge transport in metal oxide (Fe2O3, BiVO4) semiconductor photoanodes towards solar fuel generation

“…Titanium dioxide (TiO 2 ) is one of the well documented PEC oxidation materials as it possesses appropriate VB position towards water oxidation, excellent chemical stability and photocatalytic activity. However, their UV activated band gap energy (Eg~3.2 eV) is inadequate to demonstrate the solar light driven PEC process as it absorbs only 5% light photons from visible light region [11]. As a consequence, narrow band gap energy semiconductor materials are proposed to replace the TiO 2 in solar light driven PEC oxidation process.…”