Boosting Hydrogen Evolution Performance of a CdS-Based Photocatalyst: In Situ Transition from Type I to Type II Heterojunction during Photocatalysis

Abstract

The heterojunction in photocatalysis establishes an internal electric field between the semiconductors, which is one of the effective methods for enhancing the separation of photogenerated carriers of semiconductors. Herein, a strategy is rationally proposed, which is performed in situ to transform the hybrid photocatalyst composed of the Ni–Co Prussian blue analogue (PBA) and CdS (CP) into another more active hybrid photocatalyst consisting of NiS and CdS (CN) during photocatalysis in the sulfur sacrificial reagent. The coupled component on the n-type CdS is converted from an n-type Ni–Co PBA to another p-type NiS during the process, thus constructing a p–n heterojunction and achieving a good photocatalytic hydrogen evolution reaction (HER) performance. Moreover, the carrier transfer mechanism is also an in situ transition from type I in CP to type II in CN during the HER process, which is supported by surface photovoltage and transient absorption spectroscopy. The CP-2 photocatalyst in the sulfur sacrificial reagent has a high photocatalytic hydrogen evolution amount of 176.6 μmol, which is 13.9 times higher than that of pure CdS. Overall, this work develops an in situ carrier transfer mechanism conversion strategy for expanding the HER photocatalysts and enhancing their photocatalytic HER performance.

Ultrathin Bi2Se3/CdS composite for efficient photocatalytic hydrogen evolutionviahigh interfacial charge separation and photothermal effect

“…3c and d, two peaks at the binding energies of 157.57 eV and 162.77 eV correspond to Bi 4f 7/2 and Bi 4f 5/2 of Bi 3+ , while the peaks of Se 3d (Se 3d 5/2 and Se 3d 3/2 ) are displayed in the region of about 52–54 eV, belonging to Se. 2–23 However, due to the low content and ultrathin nanosheet structure of Bi 2 Se 3 in BSCS2, it is difficult to judge the spectra of Bi 4f and Se 3d of BSCS2. 38 As shown in Fig.…”

“…[14][15][16] The conventional heterojunction is of three different types, including type-I, type-II, and type-III. 17 Yu et al prepared NiS x /CdS photocatalyst to improve photocatalytic H 2 evolution by unravelling unsaturated edge S in amorphous NiS x . 18 Ding et al designed CdS modified with dual cocataysts for enhanced H 2 generation.…”

Growing COFsin situon CdS nanorods as core–shell heterojunctions to improve the charge separation efficiency

“…4–8 It has been well-proven that heterojunction construction can inhibit the recombination of photogenerated carriers and accelerate charge transfer; thus, it is an effective strategy to enhance photocatalytic activity. 9–13…”

“…[4][5][6][7][8] It has been well-proven that heterojunction construction can inhibit the recombination of photogenerated carriers and accelerate charge transfer; thus, it is an effective strategy to enhance photocatalytic activity. [9][10][11][12][13] Covalent organic frameworks (COFs) are a new type of porous crystalline material formed by the covalent connection of small organic molecules. [14][15][16] The p-stacking structure between the COF layers provides a specic path for charge carrier transport to accelerate the separation of photogenerated carriers.…”

A novel geo-photocatalyst, an iron-containing layered clay mineral, for photocatalytic H2 evolution from water

“…Since the discovery of overall water splitting (hydrogen and oxygen evolution from water) by Honda and Fujishima, 4 in which incident photon energy from UV irradiation is utilized to drive the energetically uphill water splitting reaction on the surface of the photocatalyst, various semiconductors have been used to produce H 2 from water. [5][6][7][8][9] Meanwhile, materials possessing remarkable activities with associated characteristics such as environmentally benign nature, cost-effectiveness, stability and processability are seriously required. Therefore, it is of significance to explore new photocatalysts to address the afore-mentioned challenges.…”