Robust water splitting on staggered gap heterojunctions based on WO3∖WS2–MoS2 nanostructures
2020
Mojaddami, Majdoddin | Simchi, Abdolreza
The high charge carrier recombination rate and weak oxygen evolution kinetics have impeded the efficiency of WO₃ photoelectrodes for water splitting. We present a novel type II heterojunction semiconductor based on mixed WS₂ and MoS₂ nanosheets on WO₃ nanoflakes hydrothermally grown on highly porous W skeletons. The chemically exfoliated transition metal dichalcogenide (TMD) sheets with submicrometric lateral sizes were deposited on the surface of WO₃ nanoflakes by the electrophoretic technique to fabricate a staggered gap heterojunction. The photoanode exhibited an impressive current density of 14.9 mA cm⁻² at 1.23 VRHE which comprised ∼1.7 mA cm⁻² photocurrent under 100 mW cm⁻² simulated sunlight. Co-deposition of MoS₂ and WS₂ sheets on WO₃ nanoflakes improved the current density of porous W∖WO₃ electrodes by about 340%, while only about 36% improvement is achieved by deposition of single TMD (WO₃∖MoS₂ or WO₃∖WS₂) demonstrating the synergetic effects of TMDs. The high stability of the photoanode in highly acidic media is shown. The synergetic effects of TMDs on active sites, charge transfer resistance, and charge transport properties are elaborated by electrochemical impedance spectroscopy and Mott-Schottky analyses. The composite electrode has a great potential to be used for diverse electrochemical applications including water splitting.
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