Efficient Visible-Light Photocatalytic Hydrogen Evolution and Enhanced Photostability of Core/Shell CdS/g-C₃N₄ Nanowires

Abstract

CdS/g-C3N4 core/shell nanowires with different g-C3N4 contents were fabricated by a combined solvothermal and chemisorption method and characterized by X-ray powder diffraction, scanning electronic microscopy, transmission electron microscopy, and UV-vis diffuse reflection spectroscopy. The photocatalytic hydrogen-production activities of these samples were evaluated using Na2S and Na2SO3 as sacrificial reagents in water under visible-light illumination (λ≥420 nm). The results show that after a spontaneous adsorption process g-C3N4 is successfully coated on CdS nanowires with intimate contact and can significantly improve the photocatalytic hydrogen-production rate of CdS nanowires, which reaches an optimal value of up to 4152 μmol h(-1) g(-1) at the g-C3N4 content of 2 wt %. More importantly, g-C3N4 coating can substantially reinforce the photostability of CdS nanowires even in a nonsacrificial system. The synergic effect between g-C3N4 and CdS, which can effectively accelerate the charge separation and transfer corrosive holes from CdS to robust C3N4, was proposed to be responsible for the enhancement of the photocatalytic activity and photostability. The possible conditions necessary for the synergic effect to work in a CdS/g-C3N4 core/shell configuration is also discussed.

g-C3N4-Based Nanomaterials for Visible Light-Driven Photocatalysis

“…The resulting TiO 2 /g-C 3 N 4 heterostructures possess a narrow band gap and good photoactivity (556 µmol −1 ·g −1 ) for H 2 evolution under visible-light irradiation compared to pure g-C 3 N 4 (108 µmol·h −1 ·g −1 ) or TiO 2 (130 µmol·h −1 ·g −1 . Core@shell heterojunction nanocomposites have additional advantages due to a high interfacial contact area between the shell and core components [104]. For example, CdS@g-C 3 N 4 core/shell nanowires [104] with different g-C 3 N 4 contents were prepared by a combined solvothermal and chemisorption method ( Figure 18) in which g-C 3 N 4 uniformly adsorbs over CdS nanowires resulting in enhanced improved photocatalytic H 2 production of 4152 µmol·h -1 ·g -1 for 2 wt % g-C 3 N 4 .…”

“…Core@shell heterojunction nanocomposites have additional advantages due to a high interfacial contact area between the shell and core components [104]. For example, CdS@g-C 3 N 4 core/shell nanowires [104] with different g-C 3 N 4 contents were prepared by a combined solvothermal and chemisorption method ( Figure 18) in which g-C 3 N 4 uniformly adsorbs over CdS nanowires resulting in enhanced improved photocatalytic H 2 production of 4152 µmol·h -1 ·g -1 for 2 wt % g-C 3 N 4 . A one-step self-assembly route was recently developed to fabricate core-shell architecture comprising carbon spheres decorated by g-C 3 N 4 .…”

“…The design of g-C 3 N 4 heterojunction photocatalysts is an attractive strategy to tune the electronic structure and redox potentials for visible-light absorption photocatalytic H 2 generation. Table 1 Reprinted with permission from [104]. Copyright 2013 American Chemical Society.…”

Synthesis of g-C3N4/Bi2O3/TiO2 composite nanotubes: enhanced activity under visible light irradiation and improved photoelectrochemical activity

“…For TiO 2 , n is 4 for the indirect transition. 24 Thus, plots of (ahn) 1/2 versus photon energy (hn) are obtained. As shown in Fig.…”

“…23,24 Moreover, g-C 3 N 4 has high chemical and thermal stability with narrower band gap energy (E g ) of 2.7 eV (ref. 23) than TiO 2 .…”