Optimizing the Activity of Nanoneedle Structured WO₃ Photoanodes for Solar Water Splitting: Direct Synthesis via Chemical Vapor Deposition

Abstract

Solar water splitting is a promising solution for the renewable production of hydrogen as an energy vector. To date, complex or patterned photoelectrodes have shown the highest water splitting efficiencies, but lack scalable routes for commercial scale-up. In this article, we report a direct and scalable chemical vapor deposition (CVD) route at atmospheric pressure, for a single step fabrication of complex nanoneedle structured WO3 photoanodes. Using a systematic approach, the nanostructure was engineered to find the conditions that result in optimal water splitting. The nanostructured materials adopted a monoclinic γ-WO3 structure and were highly oriented in the (002) plane, with the nanoneedle structures stacking perpendicular to the FTO substrate. The WO3 photoanode that showed the highest water splitting activity was composed of a ∼300 nm seed layer of flat WO3 with a ∼5 μm thick top layer of WO3 nanoneedles. At 1.23 VRHE, this material showed incident photon-to-current efficiencies in the range ∼35–45% in the UV region (250–375 nm) and an overall solar predicted photocurrent of 1.24 mA·cm–2 (∼25% of the theoretical maximum for WO3). When coupled in tandem with a photovoltaic device containing a methylammonium lead iodide perovskite, a solar-to-hydrogen efficiency of ca. 1% for a complete unassisted water splitting device is predicted

Heterojunction α‐Fe2O3/ZnO Films with Enhanced Photocatalytic Properties Grown by Aerosol‐Assisted Chemical Vapour Deposition

“…Therefore, to improvet he outdoor efficacy and indoor use of photocatalysts, researchers have attempted to develop materials with bandgape nergies that fall in the visible. [3] Various strategies have been applied in the development of visible-light active photocatalysts, including impurityd oping (e.g.,N:TiO 2 ), [4] surfacem odification (e.g.,p hosphates), [5] nanostructuring (e.g.,n anoneedles) [6] and the use of co-catalysts (e.g.,P t). [7] However,r ecent studies have shown that one of the most promising strategiesf or improving photocatalytic activity is to form ah eterojunction.…”

Effect of Film Thickness on Photoelectrochemical Performance of SnO2 Prepared via AACVD

“…Photoelectrochemical (PEC) water splitting is one of the most promising approaches to store clean and abundant solar energy in form of hydrogen. This technology utilizes semiconducting materials such as BiVO 4 , Fe 2 O 3 , and WO 3 as photoanode to initiate the PEC process. The performance of semiconductor in this system depends strongly on the intrinsic properties of photoanode material as well as morphological properties of the thin film including surface roughness, structure (nanoparticles, nanorods, nanosheets, and so on), and film thickness.…”

Photocatalytic and Photoelectrochemical Systems: Similarities and Differences

“…Studies indicate that the longitudinal direction of 1D crystalline nanostructures can serve as a preferential pathway for electron migration . Nanotubes, nanorods, nanowires, nanofibers, and nanoneedles are among the typical 1D nanostructured photoactive semiconductors that have been grown on substrates for photoelectrochemical applications . Grimes and co‐workers demonstrated the presence of less‐localized charge carriers in a 1D nanostructure when compared to the same material in a 0D form which favored solar energy conversion applications .…”