Hierarchical CdMoO₄ nanowire–graphene composite for photocatalytic hydrogen generation under natural sunlight

Abstract

Herein, a facile in situ solvothermal technique for the synthesis of a CdMoO 4 /graphene composite photocatalyst is reported. Graphene oxide (GO) was synthesised by an improved Hummers' method and was further used for the in situ synthesis of graphene via GO reduction and the formation of a CdMoO 4 nanowire/graphene composite. The structural phase formation of tetragonal CdMoO 4 was confirmed from X-ray diffraction measurements. The small nanoparticle assembled nanowires, prismatic microsphere morphology and crystalline nature of the synthesized material were investigated using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Due to its unique morphology and stability, the CdMoO 4 /graphene composite was used as a photocatalyst for H 2 O splitting. In comparison to pristine CdMoO 4 , the CdMoO 4 /graphene composite showed the best hydrogen evolution rate, i.e. 3624 mmole h À1 g À1 , with an apparent quantum yield of 30.5%. The CdMoO 4 /graphene composite has a higher photocatalytic activity due to the inhibition of charge carrier recombination. H 2 production measurements showed that the ternary semiconductor/graphene composite has enhanced photocatalytic activity for H 2 generation.

Unique CdS@MoS2 Core Shell Heterostructure for Efficient Hydrogen Generation Under Natural Sunlight

“…The photo-generated h + in VB consumed by sulfide S 2− and sulfite SO 3 2− enabling the effective separation of charge carriers 40 . While, e − in CB reduces the two H 2 O molecule into one H 2 gas molecule 12 . The advantages and detailed mechanism of S 2− /SO 3 2− as scavenger is well discussed in literature by Bahnemann et al .…”

“…The transition metal oxide semiconductor catalyst such as ZnO and TiO 2 reported for best photocatalytic activity. Along with ZnO and TiO 2 some other oxide catalyst such as SnO 2 4 , Ta 2 O 5 5 , Nb 2 O 5 6 , Co 3 O 4 7 , WO 3 8 , V 2 O 5 9 , MoO 3 10 , Bi 2 MoO 4 11 , and CdMoO 4 also reported 12 . But these materials have wide band gap (>3.0 eV) and show good activity only under UV light which is only 5% of the solar spectrum and did not show good photocatalytic activity in the visible light 13 .…”

Review on the Application of Semiconductor Heterostructures in Photocatalytic Hydrogen Evolution: State-of-the-Art and Outlook

“…Among the semiconductor photocatalysts reported in the known literatures, transition metal oxides usually exist superior photocatalytic activity. However, the photocatalytic activity in visible light is often less than perfect state due to their excessively wide band gap. − Although transition metal sulfide semiconductor materials have a narrow band gap and suitable VB structure, they are unstable to a certain extent because they consume the generated holes in the photocatalytic reaction and thus undergo their own oxidation, so they are usually combined with other semiconductor materials to improve their stability and photocatalytic efficiency . Cadmium sulfide (CdS), a classical transition metal sulfide semiconductor material, is widely applied in photocatalytic hydrogen evolution and water splitting reaction due to its appropriate proton reduction potential and narrow visible light absorption band system. ,− Meanwhile, the shortcoming of CdS is also obvious that its photocatalytic activity is highly limited by the severe compounding of photogenerated carriers and holes.…”

Influence of yttrium doping on the nonlinear optical limiting properties of cadmium molybdate nanostructures

“…All of the peaks were identied and matches well with the reported values. [29][30][31][32] The decrease in peak intensity of the Raman spectrum on doping conrms the proper substitution of Y 3+ into the CdMoO 4 lattice. Fig.…”