Au Nanostructure-Decorated TiO₂ Nanowires Exhibiting Photoactivity Across Entire UV-visible Region for Photoelectrochemical Water Splitting

Abstract

Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV-visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV-visible light for solar fuel production.

Enhanced photoelectrochemical and photocatalytic activities of CdS nanowires by surface modification with MoS2 nanosheets

“…Hydrogen production by solar water splitting with semiconductor photocatalysts is a promising technology based on renewable resources [1,2]. Since the first report on water splitting by Fujishima and Honda, TiO 2 has been extensively investigated as an excellent photocatalyst due to its good stability, non-toxicity, low cost and high photocatalytic activity under UV light irradiation [3][4][5]. However, TiO 2 can only absorb UV light that makes up approximately 5% of sunlight, resulting in low light utilization efficiency [6].…”

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

“…Hybrid photocatalytic systems developed by anchoring DMAP- 20 Au NPs on N-TiO 2 nanowires exhibit interesting optical and photocatalytic properties for water oxidation. Nitrogen doping of TiO 2 both maximizes the DMAP-Au NPs loading and improves the optical absorption due to band narrowing effect.…”

“…4b), the peaks at 396.8, 398.8, and 400.6 eV provide a clear picture of nitrogen environment at TiO 2 NWs. The peak at 396.8 eV is 20 attributed to the existence of atomic β-N at TiO 2 matrix and the peak at 398.8 eV implies the substitution of O 2 -by nitrogen ions and thus, results in the formation of N-Ti-O. 42,43 This confirms the existence of Ti 3+ due to the incorporation of nitrogen atoms into oxygen lattice sites.…”

“…14, 15 In the case of TiO 2 -Au hybrid photocatalytic systems, neither individual Au NPs nor significantly enhancing the UV photocatalysis of TiO 2 . [17][18][19][20][21] 29 In the present study, we investigate the underlying mechanism behind the single-step anchoring of DMAP capped Au NPs on TiO 2 nanowires and their 20 respective interactions were studied using theoretical simulations based on first principle theory. The interaction between DMAP capped Au NPs and TiO 2 nanowires were modulated via nitrogen doping the TiO 2 .…”

Research Update: Strategies for efficient photoelectrochemical water splitting using metal oxide photoanodes

“…[112][113][114] The reports attributed the enhancements by the Au attachments mainly to hot electron transfers to semiconductors. Zhang et al demonstrated that Au nanocrystals attached to photonic crystal substrate composed of TiO 2 nanotubes yielded a photocurrent density of ca.…”