Shiying Zhang

A facile spray pyrolysis method to prepare Ti-doped ZnFe2O4 for boosting photoelectrochemical water splitting

Although spinel zinc ferrite (ZnFe2O4), with a band gap of 1.9 eV, is a promising photoanode material for solar water splitting, its photoelectrochemical performance is usually hindered by poor charge carrier transport. Ti4+ doping was introduced to increase the charge carrier concentration and promote charge carrier transport in the ZnFe2O4 photoanode. Here, pure and Ti4+-doped ZnFe2O4 photoanodes were prepared by a fast and effective spray pyrolysis method. In the Ti-doped ZnFe2O4 photoanode, some of the Fe3+ sites in the crystal lattice are substituted by Ti4+, as shown by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometry (FTIR) analyses. The results of Mott–Schottky analysis and electrochemical impedance spectroscopy (EIS) indicated that the substitution of Fe3+ by Ti4+ enhances the charge carrier concentration and electron transfer efficiency. The Ti-doped ZnFe2O4 photoanodes exhibit a solar water-splitting photocurrent of 0.35 mA cm−2 at 1.23 V vs. RHE (reversible hydrogen electrode), which is 8.75 times higher than that of the pure ZnFe2O4 photoanodes. Hence, this study may provide a simple route to fabricate multi-metal oxide photoelectrodes through ion doping to enhance their photoelectrochemical performances.

Simultaneous Realization of Enhanced Photoactivity and Promoted Photostability by Multilayered MoS2 Coating on CdS Nanowire Structure via Compact Coating Methodology

CdS has been regarded as a promising photocatalytic water-splitting visible-light photocatalyst, but low catalytic activity and photocorrosion seriously limited its practical application. Here, inspired by core-shell principles, we try to fabricate CdS@MoS2 core-shell structures by utilizing unstable CdS nanowires as core and multilayered MoS2 as shell. Multilayered MoS2 not only serves as a protective shell to preserve CdS but also provides abundant reactive sites and forms a type I junction, giving rise to remarkable hydrogen production activities. The optimum hydrogen production rate based on CdS@MoS2 core-shell composite reaches 26.14 mmol·h-1·g-1, which is about 54 times greater than that of pure CdS and about twice that of CdS nanowires with 1% Pt. Impressively, the presentation of MoS2 nanosheets can effectively avoid photocorrosion, which resulted in 12 h stable hydrogen production.

Near-infrared-activated NaYF4:Yb3+, Er3+/Au/CdS for H2 production via photoreforming of bio-ethanol: plasmonic Au as light nanoantenna, energy relay, electron sink and co-catalyst

A sandwich-structured NaYF4:Yb3+, Er3+/Au/CdS architecture, as an up-conversion-involved photocatalyst for H2 production through photoreforming of renewable bio-ethanol, was constructed successfully. The Au nanoparticles embedded in the NaYF4:Yb3+, Er3+/CdS interface play a quadruplex role to improve the solar utilization efficiency. First, plasmonic Au works as a light nanoantenna to harvest more incident light. Second, plasmonic Au acts as an energy relay, in which Au SPR-induced Forster resonance energy transfer (FRET) and plasmonic resonance energy transfer (PRET) synergistically facilitate the energy transfer from NaYF4:Yb3+, Er3+ to Au to CdS. Third, Au acts as an electron sink to promote electron–hole separation. Lastly, Au serves as a co-catalyst to activate H2 evolution from bio-ethanol. The multifunctional Au makes NaYF4:Yb3+, Er3+/Au/CdS exhibit enhanced NIR-driven photocatalytic bio-ethanol reforming activity. Moreover, NaYF4:Yb3+, Er3+/Au/CdS shows superior photoactivity under simulated sunlight. This unique fabrication has implications for the rational design of highly efficient solar-energy-harvesting devices.