High efficiency Bi2S3/Bi2MoO6/TiO2 photoanode for photoelectrochemical hydrogen generation

Abstract

The ternary Bi2S3/Bi2MoO6/TiO2 photoanode with waterfall-type energy level structure was engineered firstly for photoelectrochemical (PEC) water-splitting hydrogen generation. The results of XRD, SEM, EDS and TEM illustrated that Bi2MoO6 flakes were self-assembled in flower-ball shape on TiO2 nanoparticles via solvothermal reaction and the “green” Bi2S3 quantum dots (QDs) distributed in Bi2MoO6 flake edge through in-situ anion exchange process. UV-Vis. DRS and PL spectra showed that Bi2S3 QDs broadened the response range in visible and near-infrared region and waterfall-type energy level structure is helpful to inhibit the recombination of photo-generated electrons and holes. EIS spectra proved that Bi2S3 QDs amount and size can affect significantly photoanode/electrolyte interface transfer resistance and the minimum is down to 14.20 kΩ/cm2. The PEC device comprised with Bi2S3/Bi2MoO6/TiO2 photoanode, Ag/AgCl reference electrode, Pt counter electrode and Na2SO4 solution electrolyte exhibited high performance for water splitting: the photocurrent density maximum is 21.42 mA/cm2 and the applied bias photon-to-current efficiency (ABPE) maximum is 20.8%. However, the stability of PEC cell samples is a little poor and ABPE declines to 7.28% after 12 h. The ternary Bi2S3/Bi2MoO6/TiO2 photoanode with waterfall-type energy level structure can be also employed in other photovoltaic devices besides PEC cells.