InP nanopore arrays for photoelectrochemical hydrogen generation

A Simple Fabrication of Sb2S3/TiO2 Photo-Anode with Long Wavelength Visible Light Absorption for Efficient Photoelectrochemical Water Oxidation

An Sb₂S₃-sensitized TiO₂ (Sb₂S₃/TiO₂) photo-anode (PA) exhibiting a high photo-electrochemical (PEC) performance in water oxidation has been successfully prepared by a simple chemical bath deposition (CBD) technique. Herein, the Raman spectra and XPS spectrum of Sb₂S₃/TiO₂ confirmed the formation of Sb₂S₃ on the TiO₂ coatings. The Sb₂S₃/TiO₂ photo-anode significantly shifted the absorption edge from 395 nm (3.10 eV) to 650 nm (1.90 eV). Furthermore, the Sb₂S₃/TiO₂ photo-anode generated a photo-anodic current under visible light irradiation below 650 nm due to the photo-electrochemical action compared with the TiO₂ photo-anode at 390 nm. The incident photon-to-current conversion efficiency (IPCE = 7.7%) at 400 nm and -0.3 V vs. Ag/AgCl was 37 times higher than that (0.21%) of the TiO₂ photo-anodes due to the low recombination rate and acceleration of the carriers of Sb₂S₃/TiO₂. Moreover, the photo-anodic current and photostability of the Sb₂S₃/TiO₂ photo-anodes improved via adding the Co²⁺ ions to the electrolyte solution during photo-electrocatalysis.

A one-step method to fabricate novel three-dimensional GaP nanopore arrays for enhanced photoelectrochemical hydrogen production

Gallium phosphide nanopore arrays with unique three-dimensional interior architectures (3D GaP NPs) are fabricated by electrochemical etching in a neutral solution. As the photoanodes for photoelectrochemical (PEC) hydrogen production, the 3D GaP NPs exhibited a larger photocurrent density (5.65 mA cm^-2 at 0 V vs. RHE, which is 58.3 and 2.3 times as large as that of the planar wafer and the NPs reported by our group in our previous work respectively) and a lower onset potential (-0.58 V vs. RHE, shifting negatively nearly 300 mV compared with its counterparts in the previous work). Besides the excellent light-trapping characteristics of the nanostructures, electrochemical impedance spectroscopy (EIS) further confirmed that the enhanced PEC performance was ascribed to the more efficient charge separation and transfer, and the increased surface area with the unique 3D NP arrays. Furthermore, the efficient charge separation may be attributed to the passivated surface states by the neutral solution.

Unique Three-Dimensional InP Nanopore Arrays for Improved Photoelectrochemical Hydrogen Production

Ordered three-dimensional (3D) nanostructure arrays hold promise for high-performance energy harvesting and storage devices. Here, we report the fabrication of InP nanopore arrays (NPs) in unique 3D architectures with excellent light trapping characteristic and large surface areas for use as highly active photoelectrodes in photoelectrochemical (PEC) hydrogen evolution devices. The ordered 3D NPs were scalably synthesized by a facile two-step etching process of (1) anodic etching of InP in neutral 3 M NaCl electrolytes to realize nanoporous structures and (2) wet chemical etching in HCl/H3PO4 (volume ratio of 1:3) solutions for removing the remaining top irregular layer. Importantly, we demonstrated that the use of neutral electrolyte of NaCl instead of other solutions, such as HCl, in anodic etching of InP can significantly passivate the surface states of 3D NPs. As a result, the maximum photoconversion efficiency obtained with ∼15.7 μm thick 3D NPs was 0.95%, which was 7.3 and 1.4 times higher than that of planar and 2D NPs. Electrochemical impedance spectroscopy and photoluminescence analyses further clarified that the improved PEC performance was attributed to the enhanced charge transfer across 3D NPs/electrolyte interfaces, the improved charge separation at 3D NPs/electrolyte junction, and the increased PEC active surface areas with our unique 3D NP arrays.