Hybrid photoelectrochemical–photocatalytic hydrogen evolution reaction with reduced graphene oxide–binary metal chalcogenide composites

Abstract

Summary In this study, a novel hybrid photoelectrochemical (PEC)–photocatalytic (PC) hydrogen evolution reaction (H‐PEC@PC@HER) reactor was developed, in which, the PC and PEC hydrogen evolution reactions were simultaneously performed to maximize the light absorption and investigated the synergetic interactions between these processes. Solvothermally synthesized reduced graphene oxide (RGO)‐Cd0.60Zn0.40S‐Pt composite was used as the functional photocatalyst for these reactions in H‐PEC@PC@HER reactor. The illumination of the RGO‐Cd0.60Zn0.40S‐Pt photocatalyst and photoanode was provided at the same time, thus while some of the incoming light was absorbed by the RGO‐Cd0.60Zn0.40S‐Pt photocatalyst, the light passing without being absorbed was also absorbed by the photoanode. Consequently, the utilization of the solar light spectrum was maximized with the PC reaction of RGO‐Cd0.60Zn0.40S‐Pt powder and PEC reaction of RGO‐Cd0.60Zn0.40S‐Pt photoanode. The results showed that the hydrogen production rate in the H‐PEC@PC@HER increased ca. 8.2% with respect to that of the single PC reaction. It was observed that the hydrogen production rate in the H‐PEC@PC@HER system enhanced with time due to the enhancing PEC reaction in the residual Na2S/Na2SO3 electrolyte. When compared with the results in fresh electrolyte, the photocurrent density of the RGO‐Cd0.60Zn0.40S‐Pt photoelectrode increased from 1.0 to 1.41 mA/cm2 in the residual Na2S/Na2SO3 electrolyte with a reported enhancement of 17.4% in the photocurrent density. It was proposed that S2O32− ions produced with the PC reaction were used as the hole‐recleavaging reagent of the RGO‐Cd0.60Zn0.40S‐Pt photoelectrode in the PEC system.

Synthesis and improved photoelectrochemical performances of oxygen-deficient TiO2/black-BaTiO3/CdS multiple-heterojunction nanoarrays

“…This decrease can be interpreted by the consumed sacrificial electrolyte and reduced electrolyte concentration. 46 Consequently, the surface of the TiO 2 /B-BTO/CdS composite film lacks protection, and any deterioration at the interface may reduce the photocurrent. This photocorrosion could be addressed by surface treatment of the photoanode structure, providing a potential strategy for improved stability, as proposed previously.…”

“…44,45 Typically, Na 2 S/ Na 2 SO 3 aqueous solutions were used as sacrificial electrolytes. 46 Na 2 S produces unstable S 2− anions, leading to an increase in photogenerated holes that tend to oxidize Na 2 S, thereby protecting the photoanode. Meanwhile, the S 2− and SO 3 2− anions consume holes and hinder the recombination of photogenerated electrons and holes, 46 thus increasing the production of the photocurrent.…”

“…46 Na 2 S produces unstable S 2− anions, leading to an increase in photogenerated holes that tend to oxidize Na 2 S, thereby protecting the photoanode. Meanwhile, the S 2− and SO 3 2− anions consume holes and hinder the recombination of photogenerated electrons and holes, 46 thus increasing the production of the photocurrent. Thus, in this work, a mixture of 0.35 M Na 2 S/0.25 M Na 2 SO 3 (pH ≈ 13) was used as the electrolyte.…”

Highly efficient photocatalytic H 2 evolution over Ni‐doped Mn 0. 5 Cd 0 . 5 S nanorods under visible light

“…13,14 It is advisable to promote the combination of CdS and other sulfides, leading to the formation of solid solutions, which can balance the redox ability and the light absorption ability, resulting in a better catalytic performance. [15][16][17] In particular, Mn x Cd 1Àx S (0 < x < 1) exhibits superior activity due to its regulable band structures and relatively wider visible-light response range. 18,19 However, the rapid electron-hole recombination rate severally limits its H 2 production efficiency.…”

“…Cadmium sulfide (CdS) has received extensive attention due to its better H 2 production activity than most of the existing catalysts 13,14 . It is advisable to promote the combination of CdS and other sulfides, leading to the formation of solid solutions, which can balance the redox ability and the light absorption ability, resulting in a better catalytic performance 15‐17 . In particular, Mn x Cd 1− x S (0 < x < 1) exhibits superior activity due to its regulable band structures and relatively wider visible‐light response range 18,19 .…”