Tailored TiO₂ Protection Layer Enabled Efficient and Stable Microdome Structured p‐GaAs Photoelectrochemical Cathodes

Abstract

Group III–V compound semiconductors are a promising group of materials for photoelectrochemical (PEC) applications. In this work, a metal assisted wet etching approach is adapted to acquiring a large‐area patterned microdome structure on p‐GaAs surface. In addition, atomic layer deposition is used to deposit a TiO2 protection layer with controlled thickness and crystallinity. Based on a PEC photocathode design, the optimal configuration achieves a photocurrent of −5 mA cm−2 under −0.8 V versus Ag/AgCl in a neutral pH electrolyte. The TiO2 coating with a particular degree of crystallization deposited via controlled temperature demonstrates a superior stability over amorphous coating, enabling a remarkably stable operation, for as long as 60 h. The enhanced charge separation induced by favorable band alignment between GaAs and TiO2 contributes simultaneously to the elevated solar conversion efficiency. This approach provides a promising solution to further development of group III–V compounds and other photoelectrodes with high efficiency and excellent durability for solar fuel generation.

3D Holey‐Graphene Architecture Expedites Ion Transport Kinetics to Push the OER Performance

“…This could be attributed to the unexpected negative effect on the electronic transportation property, which resulted from the introduction of oversize of nanoholes on graphene. This indicated the significance of the balance between the modulation of electron transport behaviors inside the graphene framework and ion transport behaviors at the electrode/electrolyte interface throughout electrodes including catalytical electrodes [ 34,35 ] and photoelectrochemical electrodes, [ 36,37 ] especially for ones with complex morphology structures. [ 38 ] Breaking through the traditional optimization strategies in terms of active site amount and intrinsic activity, this work puts forward a novel concept of synergistic modulation of catalytic performance from both supply side (reactive ion transport) and the consumer side (active site).…”

Quantum Dots‐Based Photoelectrochemical Hydrogen Evolution from Water Splitting

“…To achieve efficient charge separation, [68] n-type semiconductors are required as electron acceptors [36b,d,44b,d,e,69] (Figure 3a). Narrower bandgap semiconductors (e.g., CdTe, [70] GaAs, [71] and CdS [72] ) attain high carrier mobility, controlled carrier concentrations, long lifetimes, and visible-spectrum absorption. However, their development is limited by relatively low H 2 production rates, [73] which arises from the rapid charge recombination and photocorrosion caused by their high activity under light irradiation.…”

Interface Engineering for High‐Performance Photoelectrochemical Cells via Atomic Layer Deposition Technique

“…[ 30 ] ALD‐deposited TiO 2 has been used to protect various materials. [ 31–40 ] Crystallized TiO 2 was applied for PEC cell protection because of its high structure density. A 3D‐branched ZnO NWA–CdS photoanode was fabricated by Bai et al, [ 41 ] and a protective crystallized ALD TiO 2 was deposited to elevate the PEC stability.…”

“…Recently, we reported a locally crystallized TiO 2 protection layer for the patterned GaAs photocathode stability in near‐neutral solution. [ 37 ] ( Figure 4 a) Compared with the amorphous and fully crystallized TiO 2 protection layer, this tailored TiO 2 film preserved a certain degree of structure density (Figure 4c) and good conductivity, leading to simultaneous improvements in the stability and efficiency of GaAs photocathode. This work decoupled the trade‐off effect between PEC efficiency and stability and finally achieved a lifetime of 60 h with 20% current density decay in the near‐neutral solution (Figure 4d).…”