RESUMO
Following a simple one-pot hydrothermal method, a Co9S8/Bi2S3 composite was successfully synthesized using peanut-like BiVO4 as a precursor. After hydrothermal sulfuration, BiVO4 was transformed into Bi2S3 while maintaining its original peanut-like structure. Meanwhile, Co9S8 nanoparticles were successfully coated onto the peanut-shaped surface of Bi2S3, forming an S-scheme heterojunction by in situ hydrothermal method. For the growth system of Co9S8, the special three-dimensional (3D) structure of Bi2S3 provides a good growth site for zero-dimensional (0D) Co9S8 nanoparticles, avoiding their aggregation and exposing, more reaction area of Co9S8. Moreover, the S-scheme heterojunction retains a more effective redox potential for this system and promotes the recombination of nonessential electron-hole pairs. The 0D/3D spatial structure and the construction of the S-scheme heterojunction provide a more efficient and convenient path for the transfer of photogenic charge, which greatly promotes the effective separation and diversion of the electrons. Besides, the cladding structure of the composite and the S-scheme heterojunction formed between Bi2S3 and Co9S8 complement each other for jointly improving the hydrogen production performance of Co9S8/Bi2S3.
RESUMO
An economic and effective Pt-based alloy cocatalyst has attracted considerable attention due to their excellent catalytic activity and reducing Pt usage. In this study, PtNi alloy cocatalyst was successfully decorated on the g-C3N4/GO hybrid photocatalyst via a facile chemical reduction method. The Eosin Y-sensitized g-C3N4/PtNi/GO-0.5% composite photocatalyst yields about 1.54 and 1178 times higher hydrogen evolution rate than the Eosin Y-sensitized g-C3N4/Pt/GO-0.5% and g-C3N4/Ni/GO-0.5% samples, respectively. Mechanism of enhanced performance for the g-C3N4/PtNi/GO composite was also investigated by different characterization, such as photoluminescence, transient photocurrent response, and TEM. These results indicated that enhanced charge separation efficiency and more reactive sites are responsible for the improved hydrogen evolution performance due to the positive synergetic effect between Pt and Ni. This study suggests that PtNi alloy can be used as an economic and effective cocatalyst for hydrogen evolution reaction. Graphical abstract A significant enhancement of photocatalytic H2 evolution is realized over the Eosin Y-sensitized g-C3N4/PtNi/GO composite with PtNi alloy as an efficient cocatalyst.
RESUMO
A graphene oxide (GO) solution was irradiated by a Xenon lamp to form reduced graphene oxide (RGO). After irradiation, the epoxy, the carbonyl and the hydroxy groups are gradually removed from GO, resulting in an increase of sp(2) π-conjugated domains and defect carbons with holes for the formed RGO. The RGO conductivity increases due to the restoration of sp(2) π-conjugated domains. The photocatalytic activity of EY-RGO/Pt for hydrogen evolution was investigated with eosin Y (EY) as a sensitizer of the RGO and Pt as a co-catalyst. When the irradiation time is increased from 0 to 24 h the activity rises, and then reaches a plateau. Under optimum conditions (pH 10.0, 5.0 × 10(-4) mol L(-1) EY, 10 µg mL(-1) RGO), the maximal apparent quantum yield (AQY) of EY-RGO24/Pt for hydrogen evolution rises up to 12.9% under visible light irradiation (λ ≥ 420 nm), and 23.4% under monochromatic light irradiation at 520 nm. Fluorescence spectra and transient absorption decay spectra of the EY-sensitized RGO confirm that the electron transfer ability of RGO increases with increasing irradiation time. The adsorption quantity of EY on the surface of RGO enhances, too. The two factors ultimately result in an enhancement of the photocatalytic hydrogen evolution over EY-RGO/Pt with increasing irradiation time. A possible mechanism is discussed.