In Situ Construction of Ta:Fe₂O₃@CaFe₂O₄ Core–Shell Nanorod p–t–n Heterojunction Photoanodes for Efficient and Robust Solar Water Oxidation

Abstract

In order to ameliorate the poor charge transfer characteristics of hematite (α-Fe 2 O 3 ) photoanodes for photoelectrochemical (PEC) water splitting, heterojunction formation with p-CaFe 2 O 4 is attempted. Here, we report the in situ construction of a highly crystalline p-CaFe 2 O 4 shell on the surface of n-Ta:Fe 2 O 3 nanorods to form Ta:Fe 2 O 3 @CaFe 2 O 4 core−shell nanorod p−t−n heterojunction photoanodes with a transition layer (t) between them by a combined strategy of hybrid microwave annealing (HMA) and in situ Ta doping. The successful fabrication of the elaborate heterostructure is due to effective crystallization of p-CaFe 2 O 4 by HMA and prevention of Ca diffusion by already doped Ta atoms in hematite. The optimized Ta:Fe 2 O 3 @CaFe 2 O 4 photoanode loaded with the FeNiO x cocatalyst achieves a photocurrent density of 2.70 mA cm −2 , a low onset potential of 0.63 V RHE , and long-time stability in PEC water oxidation at 1.23 V RHE under 100 mW cm −2 solar irradiation, which represent marked improvements over bare hematite photoanodes and already reported hematite-based heterojunction photoanodes.

Improving built-in electric fields for effective photocatalytic activity in the rationally designed electron transfer pathway of TiO2@MoS2/Bi2S3

“…This process ultimately leaves electrons with high reducing ability in the CB of MoS 2 . 63 Consequently, favored by the specific charge transfer mode, electrons and holes would be reserved and involved in the oxidation or reduction process, leading to the production of more ROS and ultimately, significantly enhanced photocatalytic activity.…”

Regulating a Zn/Co bimetallic catalyst in a metal–organic framework and oxyhydroxide for improved photoelectrochemical water oxidation

“…The improvement of stability is a subject worth exploring in detail, and a stable semiconductor heterojunction or a passivation layer can improve stability. 48,49…”

Surface Modifications of a Vertically Grown Nanostructure for Boosting Photoelectrochemical Water-Splitting Performance

“…In the final step, the electrons and holes undergo oxidation and reduction of water, generating hydrogen and oxygen, respectively. Various types of n- and p-type semiconductor photoelectrodes have been explored, which include WO 3 , ZnO, Fe 2 O 3 , BiVO 4 , SrTiO 3 , Ta 3 N 5 , TiO 2 , etc., as n-type photoelectrodes and Cu 2 O, CuInS 2 , CaFe 2 O 4 , etc., as p-type photoelectrodes. A comparison of the PEC activity of recently reported nanostructured materials of the above-mentioned semiconductor is provided in Table .…”