Enhanced charge separation and interfacial charge transfer of InGaN nanorods/C3N4 heterojunction photoanode

Integration of Ag Plasmonic Metal and WO3/InGaN Heterostructure for Photoelectrochemical Water Splitting

In this study, a Ag/WO₃/InGaN hybrid heterostructure was successfully developed by sputtering and molecular beam epitaxy techniques, to obtain unique Ag nanospheres adorned with cauliflower-like WO₃ nanostructure over the InGaN nanorods (NRs). Exploiting the localized surface plasmon resonance of Ag, the Ag/WO₃/InGaN heterostructure exhibited superior photoabsorption ability in the visible region (400-700 nm) of the solar spectrum, with a surface plasmon resonance band centered around 440 nm. Comprehensive analysis through photoluminescence spectroscopy, photocurrent measurements, and electrochemical impedance spectroscopy revealed that the Ag/WO₃/InGaN hybrid heterostructure significantly enhances the charge carrier separation and transfer kinetics leading to improved overall photoelectrochemical (PEC) performance. The photocurrent density of the Ag/WO₃/InGaN photoanode is 1.17 mA/cm², which is about 2.72 times higher than that of pure InGaN NRs under visible light irradiation. The photoanode exhibited excellent stability for about 12 h. From the study, it has been found that the maximum applied bias photon-to-current efficiency (ABPE) is ∼1.67% at the applied bias of 0.6 V. The improved PEC water splitting efficiency of the Ag/WO₃/InGaN photoanode is attributed to the synergistic effects of localized surface plasmon resonance (LSPR), efficient charge carrier separation and transport, and the presence of a Schottky junction. Consequently, the plasmonic metal-assisted heterojunction-based semiconductor Ag/WO₃/InGaN demonstrates immense potential for practical applications in photoelectrochemical water splitting.

Complete mineralization of phenolic compounds in visible-light-driven photocatalytic ozonation with single-crystal WO3 nanosheets: Performance and mechanism investigation

Complete mineralization of phenolic compounds into CO₂ and H₂O is desirable for removing them in wastewater, but it is challenging due to the generated recalcitrant intermediates, which requires highly effective advanced oxidation process with proper catalysts. Herein, we found that single-crystal WO₃ nanosheets (NSs)-based photocatalytic ozonation (PCO) can realize complete mineralization of phenols (phenol and 2-chlorophenol) under visible light irradiation. Almost 100% mineralization ratio of phenols was achieved through WO₃ NSs-based PCO system within short time. By comparing their performances with those of polycrystalline WO₃ nanoparticles, detecting and analyzing the intermediates, identifying the dominant radicals and conducting some electrochemical characterizations, the origin of superior catalytic activity of WO₃ NSs was uncovered, the mineralization pathways and the overall mechanism were proposed. The excellent PCO performance of WO₃ NSs was contributed to their nanosheet morphology with single-crystal microstructure and good dispersion, which can provide continuous interior channels for the photogenerated charge transport from the bulk to surface of WO₃ NSs and enough active sites for the surface reactions triggered by these charges. This work puts forwards new ideas to design highly active photocatalysts for PCO and helps deepen understanding of the catalytic mechanism of PCO.

Improved photocatalytic activity and stability of InGaN quantum dots/C3N4heterojunction photoelectrode for CO2reduction and hydrogen production

Photocatalytic conversion of CO₂to produce fuel is considered a promising approach to reduce CO₂emissions and tackle energy crisis. GaN-based materials have been studied for CO₂reduction because of their excellent optical properties and band structure. However, low photocatalytic activity and severe photocorrosion of GaN-based photoelectrode greatly limit their applications. In this work, photocatalytic activity was improved by adopting InGaN quantum dots (QDs) combined with C₃N₄nano-sheets as photoanode, and thus the efficiency of CO₂reduction and the selectivity of hydrogen production were increased significantly. In addition, the photoelectron-chemical corrosion of photoelectrodes has been apparently controlled. InGaN QDs/C₃N₄has the highest CO and H₂productions rates of 14.69μmol mol^-1h^-1and 140μmol mol^-1h^-1which were 2.2 times and 14.5 times than that of InGaN film photoelectrode, respectively. The enhancement of photocatalytic activity is attributed to C₃N₄modification and a large electric dipole forming on the surface of InGaN QDs, which facilitate the separation and transfer of photo-generated carriers and thus promote CO₂reduction reaction. This work provides a promising strategy for the development of GaN-based photoanodes with superior stability and efficiency.

Highly Efficient InGaN Nanorods Photoelectrode by Constructing Z-scheme Charge Transfer System for Unbiased Water Splitting

Unbiased photoelectrochemical water splitting for the promising InGaN nanorods photoelectrode is highly desirable, but it is practically hindered by the serious recombination of charge carrier in bulk and surface of InGaN nanorods. Herein, an unbiased Z-scheme InGaN nanorods/Cu₂ O nanoparticles heterostructured system with boosted interfacial charge transfer is constructed for the first time. The introduced Cu₂ O nanoparticles pose double-sided effect on photoelectrochemical (PEC) performance of InGaN nanorods, which enables a robust hybrid structure and induces weakened light absorption capability simultaneously. As a result, the optimized InGaN/Cu₂ O-1.5C photoelectrode with the uniform morphology exhibits an enhanced photocurrent density of ≈170 µA cm^-2 at 0 V versus Pt, with 8.5-fold enhancement compared with pure InGaN nanorods. Comprehensive investigations into experimental results and theoretical calculations reveal that the electrons accumulation and holes depletion of Cu₂ O facilitate to form a typical Z-scheme band alignment, thus providing a large photovoltage to drive unbiased water splitting and enhancing the stability of Cu₂ O. This work provides a novel and facile strategy to achieve InGaN nanorods and other catalyst-based PEC water splitting without external bias, and to relieve the bottlenecks of charge transfer dynamics at the electrode bulk and electrode/electrolyte interface by constructing Z-scheme heterostructure.

InGaN Nanorods Decorated with Au Nanoparticles for Enhanced Water Splitting Based on Surface Plasmon Resonance Effects

Photoelectrochemical (PEC) water splitting has great application potential in converting solar energy into hydrogen energy. However, what stands in the way of the practical application of this technology is the low conversion efficiency, which can be promoted by optimizing the material structure and device design for surface functionalization. In this work, we deposited gold nanoparticles (Au NPs) with different loading densities on the surface of InGaN nanorod (NR) arrays through a chemical solvent route to obtain a composite PEC water splitting system. Enhanced photocatalytic activity, which can be demonstrated by the surface plasmon resonance (SPR) effect induced by Au NPs, occurred and was further confirmed to be associated with the different loading densities of Au NPs. These discoveries use solar water splitting as a platform and provide ideas for exploring the mechanism of SPR enhancement.