Highly efficient charge transfer through a double Z-scheme mechanism by a Cu-promoted MoO₃/g-C₃N₄ hybrid nanocomposite with superior electrochemical and photocatalytic performance

Abstract

Herein, a novel Cu-MoO3/g-C3N4 hybrid nanocomposite was successfully synthesized by a two-step strategy of one-pot pyrolysis followed by the impregnation method. The structure, phase, morphology and electronic environment of MoO3, g-C3N4 and Cu in the composite were determined by various characterization methods. The oxygen vacancies of MoO3 were ascertained by UV-DRS, Raman, and XPS analysis. The formation of the heterostructure was characterised by electrochemical measurements. The photocatalytic performance of the composite was investigated by the water reduction reaction and the reduction of an important inorganic pollutant, Cr(vi). In the presence of Cu NPs, the H2 evolution of the MoO3/g-C3N4 hybrid was found to be 652 μmol h-1 with an apparent energy conversion efficiency of 13.46%, and up to 95% of Cr(vi) was reduced using citric acid as a hole scavenger. The remarkably enhanced photocatalytic performance was attributed to the combined effect of the double Z-scheme mechanism and defective MoO3. The in situ formation process of the MoO3/g-C3N4 hybrid followed a direct Z-scheme charge transfer by generating a great number of defects at the solid-solid interface, similar to that of a conductor, and offered low electrical resistance, whereas loading of Cu NPs built up an indirect Z-scheme charge transfer to establish the double Z-scheme charge transfer mechanism. This hybrid material produces a photocurrent density of 12.1 mA cm-2, in good agreement with the photocatalytic activity. This study highlights the facilitation effect of MoO3 due to oxygen vacancies and charge transfer through the double Z-scheme mechanism to open up a new window in the field of 2D nanostructured photocatalytic materials.

Heterostructured d‐Ti3C2/TiO2/g‐C3N4 Nanocomposites with Enhanced Visible‐Light Photocatalytic Hydrogen Production Activity

“…However, the high photoinduced charge‐carrier recombination rate and low photon adsorption of only blue light (450 nm) render g‐C 3 N 4 far from the performance level required for practical utilization . It is generally accepted that high photocatalytic activity could be obtained by the construction of heterostructured nanocomposites, and only type II and Z‐scheme heterostructured semiconductor photocatalysts can sufficiently improve the fast spatial separation of photoinduced electron–hole pairs, prolong their lifetime and promoting the photocatalytic activity . Furthermore, the construction of 2D–2D layered heterostructures has drawn increasing attention because it can improve the interfacial contact and possesses some unique properties that are of benefit to photocatalysis.…”

Rational Design of a Coupled Confronting Z‐Scheme System Toward Photocatalytic Refractory Pollutant Degradation and Water Splitting Reaction

“…Many research groups have reported their findings in designing unidirectional double Z‐scheme‐based photocatalysts for water redox reactions and degradation of harmful pollutants . Moreover, our group has reported photocatalytic reduction of Cr 6+ → Cr 3+ and water → H 2 over Cu–MoO 3 /g‐C 3 N 4 hybrid nanocomposite . Ternary Ag 2 CO 3 /CeO 2 /AgBr photocatalyst has been reported by Wen et al with double Z‐scheme configuration performing photodegradation of levofloxacin .…”

“…Understandably then, scientists started focusing on the construction of ternary semiconductors with dual Z‐scheme pathway for more effective charge separation. Many research groups have reported their findings in designing unidirectional double Z‐scheme‐based photocatalysts for water redox reactions and degradation of harmful pollutants . Moreover, our group has reported photocatalytic reduction of Cr 6+ → Cr 3+ and water → H 2 over Cu–MoO 3 /g‐C 3 N 4 hybrid nanocomposite .…”

Facile construction of a novel NiFe2O4@P-doped g-C3N4 nanocomposite with enhanced visible-light-driven photocatalytic activity

“…24 All the catalysts exhibited analogous PL spectra, whereas weak peaks for NFO were observed in the range of 380 nm to 500 nm, which might be ascribed to the surface oxygen vacancies and defects of NFO originating from excitonic PL. 31 Aer the addition of NFO species, an obvious decrease in the intensity of the PL spectra for P-CN was observed, suggesting that NFO modi-cation efficiently prevented electron-hole pair reunion. Finally from these characterizations, well-supporting results in favor of photoinduced charge migration and separation were obtained for 20 wt% NFO@P-CN.…”