One-pot synthesis of S-scheme MoS2/g-C3N4 heterojunction as effective visible light photocatalyst

Abstract

Despite pioneering as the holy grail in photocatalysts, abundant reports have demonstrated that g-C3N4 performs poor photocatalytic activity due to its high recombination rate of photo-induced charge carriers. Many efforts have been conducted to overcome this limitation in which the semiconductor–semiconductor coupling strategies toward heterojunction formation were considered as the easiest but the most effective method. Herein, a one-pot solid-state reaction of thiourea and sodium molybdate as precursors at different temperatures under N2 gas was applied for preparing composites of MoS2/g-C3N4. The physicochemical characterization of the final products determines the variation in contents of components (MoS2 and g-C3N4) via the increase of synthesis temperature. The enhanced photocatalytic activity of the MoS2/g-C3N4 composites was evaluated by the degradation of Rhodamine B in an aqueous solution under visible light. Therein, composites synthesized at 500 °C showed the best photocatalytic performance with a degradation efficiency of 90%, much higher than that of single g-C3N4. The significant improvement in photocatalytic performance is attributed to the enhancement in light-harvesting and extension in photo-induced charge carriers’ lifetime of composites which are originated from the synergic effect between the components. Besides, the photocatalytic mechanism is demonstrated to well-fit into the S-scheme pathway with apparent evidences.

Visible Light-Active Ternary Heterojunction Photocatalyst for Efficient CO2 Reduction with Simultaneous Amine Oxidation and Sustainable H2O2 Production

“…Moreover, the cutoff energies ( E cut‑off ) of g-C 3 N 4 , Ni 12 P 5 , and ZnIn 2 S 4 [determined from ultraviolet photoelectron spectroscopy (UPS)] were 18.60, 18.22, and 17.70 eV, respectively (Figure S10a–c), while their Fermi levels ( E f ) were all 0 eV. Consequently, the work functions ( e Φ) of these components were evaluated as 2.60, 2.98, and 3.50 eV based on the equation e Φ = h ν – | E cutoff – E f |. , Obviously, the work function value of g-C 3 N 4 (2.60 eV) is smaller than those of Ni 12 P 5 (2.98 eV) and ZnIn 2 S 4 (3.50 eV), resulting in transfer of electrons from g-C 3 N 4 to ZnIn 2 S 4 through Ni 12 P 5 nanoparticles at their heterojunction interface until their Fermi level is aligned at equilibrium. This proves that Ni 12 P 5 nanoparticles act as an electron bridge between g-C 3 N 4 and ZnIn 2 S 4 .…”

One-step thermal polymerization synthesis of nitrogen-rich g-C3N4 nanosheets enhances photocatalytic redox activity

“…1e ). 31 The spectra of N 1s can be fitted with four main peaks, which are attributed to the C–N C at 398.13 eV, N 3 C-low binding energy at 399.3 eV and N 3 C-high binding energy at 400.29 eV, and π-excitation, –NH 2 groups or N–N bonds at 403.68 eV, respectively. 32–35 By analyzing the peak area (Tables S2 and S3 † ), CN-70 showed a reduced C content and an increased N content, which further proved that the CN-70 surface is nitrogen-enriched after methanol modification.…”

Challenges surrounding nanosheets and their application to solar-driven photocatalytic water treatment

“…Reaction (R2) requires the donation of a photoexcited electron from the semiconductor to the O 2 . This electron has a minimum energy of −0.33 V vs. NHE 142,148,149 (normal hydrogen electrode). If the energy level of the photocatalyst conduction band is not sufficiently low (<−0.33 V) then the reaction will not take place.…”

“…Similarly, reaction (R1) requires the H 2 O to donate an electron to the valence band of the semiconductor in order to fill the h + formed during photoexcitation. If the valence band energy level is too negative (<2.32 V 142,148,149 ) this reaction will not occur. 150 This is illustrated in Fig.…”