Synthesis of Host‐Guest Hematite Photoelectrodes for Solar Water Splitting

Abstract

Hematite (α‐Fe2O3) is a promising semiconductor for photoelectrochemical (PEC) water splitting, due to its abundance, low‐cost and excellent stability. However, the efficiency of α‐Fe2O3 photoelectrodes has been limited by its low hole mobility and fast electron‐hole recombination. Host‐guest architectures have emerged as a suitable design, which involves the use of a nanostructured collector for high solar absorption while maintaining an ultrathin absorber layer for better charge transport. In this study, a thin mesoporous SiO2 host template coated with a conductive thin layer of TiO2 was optimized to support the α‐Fe2O3 film. The α‐Fe2O3 thin layer was deposited by spray pyrolysis and then coated with a FeNiOOH co‐catalyst. A photocurrent improvement of ca. 85% over planar α‐Fe2O3 thin film reference was registered demonstrating the potential of this host‐guest approach.

Hematite photoelectrodes grown on porous CuO–Sb2O5–SnO2 ceramics for photoelectrochemical water splitting

“…One of the approaches to improve the PEC performance of photoelectrodes can be the engineering of the conductive substrate and/or its optimization under certain photoactive material [18][19][20]. For example, the photoelectrodes fabricated according to the so-called "host-guest" strategy [35][36][37][38][39][40][41] involve the engineering of the conductive substrate aiming to increase their active surface area and to improve electron collection. This is usually reached by forming the hierarchical structure of electrodes when one layer or multilayers of photocatalytic material ("guest") are deposited on the substrate ("host") with a high surface area.…”

“…In this case, the photoactive material can be deposited on the surface by thin layers that are favorable for hole diffusion, while a good light harvesting and the electron collection are assured by 3D relief of conductive substrate and by multilayers of the photocatalytic coating. To date, such substrates have been obtained, for example, as: thin mesoporous SiO2 host template coated with a conductive thin layer of TiO2 to support the α-Fe2O3 film [36]; highly porous SnO2 nanosheet arrays sandwiched within TiO2 and CdS quantum dots [37]; 3D porous niobium doped tin oxide electrodes fabricated by atomic layer deposition [38]; self-assembled 6 nm nanocrystalline Sb-doped SnO2 spheres onto glass during a multi-step coating procedure [39]. The approach of "host-guest" strategy was implemented, for example, in the fabrication of gold nanorod substrate which was grown inside the aluminum oxide membrane to provide a conductive and nanostructured surface acting as the current collector [41].…”

Photoelectrochemical Water Splitting: Thermal Annealing Challenges on Hematite Nanowires

“…Hematite Photoanodes Preparation. FTO glass substrates (Solaronix, 7 and 10 Ω square −1 ) were cleaned as described elsewhere 39 and then placed in a 40 mL capacity Teflon stainless-steel autoclave with 20 mL of a solution comprising 0.15 M FeCl 3 •6H 2 O (99+%) and 1 M NaNO 3 (≥99.0%). The solution was adjusted to pH 1.5 using HCl 37%.…”