CdS Nanoparticles Supported on Ti₃C₂T_x MXene for the Efficient Photocatalytic Production of H₂O₂: Implications for the Photocatalytic Degradation of Emerging Contaminants

Abstract

Herein, Ti 3 C 2 T x MXene was prepared and used to anchor CdS nanoparticles, and CdS/Ti 3 C 2 T x (CT) photocatalyst with an interfacial Schottky junction was obtained for in situ hydrogen peroxide (H 2 O 2 ) production to degrade emerging contaminants. CT-0.5 photocatalyst had the highest H 2 O 2 production yield, which was 401 μmol L −1 within 1 h in pure water without organic sacrificial reagents under visible-light irradiation (λ > 420 nm), more than 3 times that of pristine CdS. The excellent photocatalytic performance was attributed to the unique properties of Ti 3 C 2 T x and the formed Schottky junction, which accelerated electron transfer and spatial charge separation. The introduction of Ti 3 C 2 T x improved the selectivity of two-electron O 2 reduction, and the direct one-step two-electron O 2 reduction route dominated the overall O 2 reduction process for H 2 O 2 production. Finally, CT-0.5 was applied to construct a photo-Fenton system, which also exhibited a superior catalytic performance and wide suitability for degrading emerging contaminants, suggesting its environmental significance. KEYWORDS: photocatalysis, in situ H 2 O 2 production, Ti 3 C 2 T x MXene, CdS, Schottky junction ■ HIGHLIGHTS • Ti 3 C 2 T x MXene supported CdS nanoparticles were synthesized and characterized. • Ti 3 C 2 T x MXene could accelerate H 2 O 2 production by CdS nanoparticles. • Ti 3 C 2 T x improved the selectivity of two-electron O 2 reduction for H 2 O 2 production. • Various pollutants could be degraded by this photocatalytic Fenton-like system.

Enhanced Photocatalytic Degradation of Emerging Contaminants Using Ti3C2Tx MXene-Supported CdS Quantum Dots

“…For n-type semiconductors, the CB potential is usually 0.1 V lower than its flat-band potential, which is equivalent to its Fermi level ( E f ) . Because the ECB and EVB of CdS were calculated to be −0.385 and 1.765 V, respectively, its E f could be estimated to be −0.285 V, which was more negative than the value of −0.08 V of Ti 3 C 2 T x MXene calculated in our previous study . Therefore, when CdS QDs were tightly attached to the Ti 3 C 2 T x MXene surface, a Schottky junction would be formed at the intimate coupling interface, accompanying the VB and CB upward bending of the CdS QDs, as the two different E f ’s must reach a new equilibrium.…”

“…16 Because the ECB and EVB of CdS were calculated to be −0.385 and 1.765 V, respectively, its E f could be estimated to be −0.285 V, which was more negative than the value of −0.08 V of Ti 3 C 2 T x MXene calculated in our previous study. 69 Therefore, when CdS QDs were tightly attached to the Ti 3 C 2 T x MXene surface, a Schottky junction would be formed at the intimate coupling interface, accompanying the VB and CB upward bending of the CdS QDs, as the two different E f 's must reach a new equilibrium. Under simulated solar irradiation, the CdS QDs catalysts were excited to produce electron−hole (e − −h + ) pairs and then photoinduced e − migrated rapidly from the CB of CdS to Ti 3 C 2 T x MXene through the formed Schottky junctions, while the formed Schottky junctions could also inhibit the recombination of photoinduced electron−hole pairs.…”

Mo2C MXene Nanosheets Made in Different Etching Solutions as Co-catalysts for Hydrogen Production

“…In light of these, it can be concluded that the composition and modification on the surface of Mo 2 C MXene can dramatically affect the intrinsic nature of MXene and the final catalytic activity. 44 The energy band structure of a semiconductor is crucial to comprehend the mechanism in photocatalysis for H 2 evolution activity. According to Figure 5a, the band gap energy (E g ) of samples can be obtained by the Tauc plots, in which (αhv) 1/n is plotted versus the photon energy (hv), where α is the absorbance derived from the UV−vis DRS in Figure 5a, n is 1/ 2 because the nature of CdS is a direct band gap material and CdS has a characteristic of n-type semiconductors, 45 and h and v are the Planck constant and irradiation frequency, respectively.…”

“…It is evident that a lower charge-transfer resistance with the smallest semicircles arc is observed for Mo 2 C MXene with Li + , which is beneficial to the fast migration of photogenerated electrons excited from CdS and thereby the effective suppression of carrier recombination. In light of these, it can be concluded that the composition and modification on the surface of Mo 2 C MXene can dramatically affect the intrinsic nature of MXene and the final catalytic activity …”

Fabrication of nitrogen-deficient g-C3N4 nanosheets via an acetaldehyde-assisted hydrothermal route and their high photocatalytic performance for H2O2 production and Cr(vi) reduction

“…Recent investigation indicates that the removal of Cr(VI) by photocatalytic reduction becomes a promising method to treat the pollution of Cr(VI) due to its distinct advantages, e.g., being fast and eco-friendly, and harnessing solar energy. [21][22][23][24][25][26][27][28][29][30] The prospect of converting sustainable solar energy into clean energy or using solar light to deal with environmental pollutants through photocatalysts has driven the search for efficient photocatalysts. 31 Among the photocatalysts explored, metal-free carbon nitride (CN) has become an extremely attractive visible light photocatalyst due to its environmental friendliness and good stability.…”