BaAu₂S₂: A Au-Based Intrinsic Photocatalyst for High-Performance Visible-Light Photocatalysis

Abstract

A new Au-based sulfide BaAuS was obtained through solid-state reaction. It crystallizes in the tetragonal space group I4/amd with unit cell parameters of a = 6.389 72(2) Å, b = 6.389 72(2) Å, c = 12.7872(1) Å, and Z = 4. Its structure features [AuS] zigzag chains composed of corner-sharing AuS linear units. With a direct band gap of 2.49 eV, BaAuS is suitable for the visible-light harvesting. Moreover, it exhibits excellent visible-light photocatalytic activity, which is 1.3 times that of graphitic carbon nitride (g-CN) and also demonstrates excellent circulating stability. On the basis of the crystal and electronic structure analysis, the electrons are highly delocalized along the [AuS] chains, and the electron effective mass of BaAuS is only approximately one-fifth of that of g-CN, which may help the separation of the electron/hole pairs during the photocatalytic process. Additionally, the absorption coefficient of BaAuS is extremely high, exceeding 1 × 10 cm over the entire absorbable visible spectrum (hν > E), which is significantly higher than that of g-CN. Such factors may contribute to its outstanding photocatalytic performances. According to our best knowledge, BaAuS is the first noble metal-based chalcogenide photocatalyst reported as intrinsic light-harvesting and electron/hole-generating centers. This study may provide valuable insights for further research on photocatalytic materials.

Crystal Chemistry and Photocatalytic Properties of RE4S4Te3 (RE = Gd, Ho, Er, Tm): Experimental and Theoretical Investigations

“…Photocurrent measurement is a common strategy to evaluate the photocatalytic activities of the catalysts. ,, Larger photocurrent usually indicates a more effective separation of photogenerated electron–hole pairs and therefore a superior photocatalytic activity. Additionally, it is well-known that the photocurrent is highly associated with the effective mass of the photogenerated electron–hole pairs.…”

“…The conduction band minimum (CBM) of Gd 4 S 4 Te 3 and Er 4 S 4 Te 3 are located at the A point, and those of other three compounds are located at the Z point (Figures 5a and S5 Theoretically speaking, a larger photocurrent tends to predict smaller photogenerated charge carrier effective mass (i.e., higher charge carrier mobility) and therefore decreases the recombination probability of the electrons and holes in semiconductors. 15,38 To understand photoexcited charge carrier mobilities and photocurrent behaviors in RE 4 S 4 Te 3 , the values of their carrier effective mass were calculated and determined from the curvatures of CBM and VBM: where m*, ℏ, E(k), and k are the carrier effective mass, reduced Planck's constant, the energy state and Brillouin zone path in reciprocal space, respectively. The effective mass of electron and hole in RE 4 S 4 Te 3 derived from the above formula (Table S3) shows an inverse proportional relationship and fits nicely to the trend of measured photocurrents (Figure S13).…”

“…On account of these advantages, it is worth investigating chalcogenides-type photocatalysts under visible light radiation. To date, there are many binary, ternary, and quaternary ones studied, including but not limited to ZnS, CdS, CuInS 2 , A I 2 -Zn-A IV -S 4 (A I = Cu and Ag; A IV = Sn and Ge), and Na 10 In 16 Cu 4 S 35 . , The predominant exploration of chalcogenide photocatalysts is focused on modifying or compositing known nanoscale ones, while the completely novel ones, are relatively less commonly addressed, limited examples including Dy 4 S 4 Te 3 , α-EuZrS 3 , BaAu 2 S 2 , LaOInS 2 , Ba 2 AsGaSe 5 , and K 8 Ce 2 I 18 O 53 . , For completely novel ones, it is better to explore them from their bulk crystalline phases since their crystal and electronic structures can be studied exactly, which are important to help understand their photocatalytic activities. Compared with the corresponding nanophases, bulk crystalline ones have much larger sizes, smaller surface areas, and uneven morphologies, so their photocatalytic performances are more or less insufficient.…”

High-Efficiency Visible Light Responsive Sulfide KSb5S8 Photocatalyst with a Layered Crystal Structure

“…Furthermore, recombination of photo-induced electrons and holes severely reduces its photocatalytic efficiency. Therefore, practical applications of TiO 2 have been limited to date [6]. Strategies such as ion doping, heterojunction construction, and noble metal loading have been developed to enhance the absorption of visible light and accelerate the separation of photo-induced electrons and holes [7][8][9][10].…”

Rational Band Design in Metal Chalcogenide Ba6Zn6HfS14: Splitting Orbitals, Narrowing the Forbidden Gap, and Boosting Photocatalyst Properties

“…Compared to the oxides, chalcogenides often possess narrow energy band gaps, which is favorable to utilize the visible-light sources. , It is imperative to design a new kind of photocatalyst in order to degrade organic dyes under visible light. According to previous reports, a large number of chalcogenides have shown good photocatalytic activity. − As an important one among numerous semiconductor compounds of group II–VI, ZnS exhibits great light catalytic and photoelectric properties owning to the photoexcited electron hole pairs’ rapid generation and excited electrons’ highly negative potentials. , It is generally regarded as a potential high-efficient photocatalyst. Unfortunately, on account of its large 3.7 eV band gap, , ZnS can only absorb UV light sources.…”