Graphene-Modified Semiconductor Photoelectrode

Photoelectrocatalytic water decomposition using semiconductor is a very attractive technique to solve the global energy and environmental problems. This technique converts the solar energy into hydrogen energy by water decomposition. Photoelectrode is an important part of this technique. Graphene-modified semiconductor photoelectrode is an excellent photoelectrode of within.

Tungsten trioxide (WO3) is an n-type indirect bandgap semiconductor with a band gap of 2.5 to 2.8 eV and a theoretical absorption sideband of 430 to 500 nm. It has unique photoelectrochemical properties. Because of its narrow band gap and high valence band potential (+3.10~3.20V vs.NHE), it is a very promising oxide semiconductor catalyst. In addition, graphene has the advantages of large specific surface area, high charge carrier mobility, low resistivity and good chemical stability. In the field of photoelectric catalysis, graphene-modified semiconductor photoelectrodes not only help to improve the conductivity of materials, Moreover, it also contributes to the absorption of light, and is also widely used in improving the photoelectrocatalytic activity of photoelectrodes. Some scholars have improved the charge transfer efficiency by co-modifying the tungsten trioxide photoelectrode by reducing graphene nickel iron oxyhydroxide. It includes the following steps:

(1) Add tungstic acid and polyvinyl alcohol to a hydrogen peroxide solution, stirring until a uniform solution is formed to obtain a seed layer solution; applying the seed layer solution to the conductive glass by spin coating, and then applying the coated conductive The glass is heated to 450-550 ° C, and after being kept for 1.5 to 3 hours, it is cooled to room temperature to obtain a substrate; wherein the amount of tungstic acid added in the hydrogen peroxide solution is 70-80 g/L, and the amount of polyvinyl alcohol added is 20 ~40g/L;

(2) Add a hydrogen peroxide solution of tungstic acid, oxalic acid, urea, and hydrochloric acid to acetonitrile, stirring to form a homogeneous solution to obtain a hydrothermal reaction liquid; and placing the substrate obtained in the step (1) in a hydrothermal reaction liquid, 160-200 ° C hydrothermal reaction for 1 to 6 hours, cooled to room temperature, taken out, washed, dried, and then incubated at 450 ~ 550 ° C for 1.5 ~ 3 hours, cooled to room temperature, to obtain tungsten trioxide nanosheet photoelectrode; The molar ratio of tungstic acid, oxalic acid, urea, hydrochloric acid and acetonitrile is (6-9): (10-20): (15-25): (100-200): (1×104-1.5×104);

(3) Apply an aqueous solution of graphene oxide to the tungsten trioxide nanosheet photoelectrode obtained in the step (2) by spin coating to obtain a graphene oxide modified tungsten trioxide photoelectrode; under an argon or nitrogen atmosphere, The graphene oxide modified tungsten trioxide photoelectrode is heated to 450-550 ° C, held for 1.5 to 3 hours, and then cooled to room temperature to obtain a reduced graphene-modified tungsten trioxide photoelectrode;

(4) The reduced graphene-modified tungsten trioxide photoelectrically active working electrode obtained by the step (3), the platinum plate is a counter electrode, and the saturated calomel electrode is a reference electrode to form a three-electrode system containing ferric chloride and nickel chloride. , 4.5 ~ 5.5mmol / L sodium fluoride, 0.08 ~ 0.12mol / L potassium chloride and 0.98 ~ 1.02mol / L hydrogen peroxide aqueous solution for the electrolyte, using cyclic voltammetry from -0.5 ± 0.05V to 0.5 ± The potential interval of 0.05V vs. SCE is circulated. Finally the working electrode is washed and dried.

The tungsten trioxide is hydrothermally grown onto the surface of the conductive glass, and then the reduced graphene and the nickel iron oxyhydroxide are attached to the surface of the semiconductor material to form a uniform promoter layer; the reductive graphene and the nickel iron oxyhydroxide are co-modified with trioxide The tungsten photoelectrode improves the conductivity of the photoelectrode and the transfer efficiency of the photo-generated carriers under the synergistic action of reducing graphene and nickel-doped iron oxyhydroxide, promotes the oxygenation reaction at the interface of the electrode, and finally improves the photoelectrocatalysis of the photoelectrode. The efficiency of decomposing water is also applicable to the modification of other semiconductors in the fields of photoelectrocatalysis, photoelectrochemical sensors and electrocatalysis.

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