Integrated p-n Junctions for Efficient Solar Water Splitting upon TiO2/CdS/BiSbS3 Ternary Hybrids for Improved Hydrogen Evolution and Mechanistic Insights

Abstract

The development of efficient and novel p-n heterojunctions for photoelectrochemical (PEC) water splitting is still a challenging problem. We have demonstrated the complementary nature of (p-type) BiSbS3 as a sensitizer when coupled with (n-type) TiO2/CdS to improve the photocatalytic activity and solar to hydrogen conversion efficiency. The as-prepared p-n heterojunction TiO2/CdS/BiSbS3 exhibits good visible light harvesting capacity and high charge separation over the binary heterojunction, which are confirmed by photoluminescence (PL) and electrical impedance spectroscopy (EIS). The ternary heterojunction produces higher H2 than the binary systems TiO2/CdS and TiO2/BiSbS3. This ternary heterojunction system displayed the highest photocurrent density of 5 mA·cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) in neutral conditions, and STH of 3.8% at 0.52 V vs. RHE is observed. The improved photocatalytic response was due to the favorable energy band positions of CdS and BiSbS3. This study highlights the p-n junction made up of TiO2/CdS/BiSbS3, which promises efficient charge formation, separation, and suppression of charge recombination for improved PEC water splitting efficiency. Further, no appreciable loss of activity was observed for the photoanode over 2500 s. Band alignment and interfaces mechanisms have been studied as well.

CuInS2 Nanosheet Arrays with a MoS2 Heterojunction as a Photocathode for PEC Water Splitting

“…The excited electrons migrate from the VB (1.07 eV vs RHE) to the CB (−0.55 eV vs RHE) of CIS NSAs. Incorporating an overlayer of n-type CdS having the CB and VB at −0.50 eV vs RHE and 1.70 eV vs RHE gives rise to a p–n junction, − resulting in the transfer of photogenerated electrons in the CIS NSA CB to CB of CdS. Then, electrons are transferred to the noble metal-free co-catalyst MoS 2 having CB and VB positions −0.23 eV vs RHE and 1.71 eV vs RHE, respectively, providing surface active sites to the H + ions for adsorption and getting reduced to H 2 with the photoexcited electrons .…”

S-Scheme System of MoS2/Co3O4 Nanocomposites for Enhanced Photocatalytic Hydrogen Evolution and Methyl Violet Dye Removal under Visible Light Irradiation

“…As exhibited in Figure 5c, with the extended amount of MC photocatalysts from 10 mg to 50 mg, the HER rate of the heterojunction system first increased then decreased. Under a photocatalytic HER reaction, owing to the charge carrier production step, both charge carrier transporting and trapping are required situations [28]. Redundant MC-4 samples arise to be significantly agglomerated and appear to be further from the crystal boundary, ultimately affecting the serious electrons and holes' recombination rate, which reduces the operation of the photocatalysts.…”

Exploring CuBi2O4 as a Promising Photocathode Material for PEC Water Splitting

“…The technology to convert water into hydrogen fuel using sunlight was shown to be effective by photoelectrochemical (PEC) cells with photoelectrodes, which are easy to transport and do not produce greenhouse gases. This is a promising method for utilizing solar energy to create chemical energy in the form of hydrogen fuel. − PEC water splitting utilizing numerous semiconductor materials has been widely investigated as a significant effort to harness solar energy. − Since Fujishima and Honda demonstrated that TiO 2 has a photocatalytic function, various semiconductor materials have been explored to enhance the STH efficiency and photostability in PEC water splitting. − PEC cell reactions are performed using a three-electrode system, where the semiconductor photoelectrode acts as the working electrode, a metal rod such as Pt serves as the counter electrode, and Ag/AgCl acts as the reference electrode. − In such a three-electrode system, the working electrode only drives one of the two half-reactions of water splitting. The other half-reaction is usually driven by an external bias applied to the counter electrode. − In the real-world application, PEC cells would be set up using a two-electrode configuration for water splitting, ideally without the use of a physical bias. − Instead of the expensive Pt, BiVO 4 can be used as a more effective, affordable, and environmentally friendly photocatalyst for water splitting.…”