Tungsten Sulfide Modified Copper Oxide Hydrogen Evolution Photoelectrode

Photoelectrochemical hydrogen evolution technology is a new energy technology. It combines photoelectric conversion process with hydrogen evolution process. Solar energy can be converted into electric energy. It can be further used to prepare hydrogen from electrolytic water by hydrogen evolution catalyst. It has great development potential.

Using WS₂ as hydrogen evolution catalyst instead of noble metal to modify semiconductor photocatalyst can obtain cheap and efficient hydrogen evolution photocatalyst. Following, the process of modifying copper oxide hydrogen evolution Photocathode with mixed phase tungsten sulfide is as follows:

(1) Cu₂O thin film electrodes prepared by electrodeposition
The pH value of the mixed solution of Cu₂SO₄ and trisodium citrate with molar ratio of 1:1 was adjusted to 10.8-11.5 by NaOH aqueous solution. The fluorine-doped tin dioxide glass (FTO glass) was used as working electrode, Ag/AgCl as reference electrode and platinum sheet electrode as counter electrode at the temperature of 60-70 ℃. The Cu₂O thin film photoelectrode was prepared by 0.5-2 H deposition under the condition of -0.4V Ag/AgCl.

(2) Intercalation stripping WS₂
The solid powder WS₂ was added into the Shrek tube. In the inert gas environment of argon or nitrogen, the n-butyl lithium required per gram of WS₂ was 0.2-0.8 g. The n-butyl lithium solution with a concentration of 2.4 mol/l was added to the Shrek tube. After reaction at 60 oC-70 oC for 20-60 h, the solid was extracted and dissolved in water. Then the unsealed WS2 was removed by centrifugation, and the solid contained in the Shrek tube was obtained. In the water solution of mixed phase tungsten sulfide (M-WS2), the mass fraction of 1T-WS₂ with metallic phase is 50%-75%.

(3)Preparation of mixed phase tungsten sulfide modified copper oxide double-layer (M-WS₂ / Cu2O) hydrogen evolution photoelectrode.

The concentration of aqueous solution containing mixed phase tungsten sulfide (M-WS₂) was adjusted to 0.2 mg/mL. At 20-25 oC, the surface of Cu₂O thin film photocathode prepared by step (1) was first immersed in the M-WS2 aqueous solution for 8-10 minutes, and then extracted at a speed of 30 cm/s. The mixed phase tungsten sulfide modified copper oxide was obtained by 5-10 times immersion-extraction double-layer hydrogen photoelectrode.

Tungsten sulfide (WS₂ ) is a recently studied cocatalyst for hydrogen evolution. It has a unique two-dimensional structure. After intercalation and stripping, single or multi-layer nano-lamellar structure can be obtained. By pairing with copper oxide, the electrocatalytic hydrogen evolution activity of the syntheses is greatly improved. Controlling the stripping conditions, the preparation of WS2 nanostructures containing 2H-WS₂ and 1T-WS₂ mixed phases and using them to modify Cu₂O photocathode can significantly improve the photoelectric conversion efficiency due to the formation of p-n heterojunction. At the same time, the hybrid phase WS₂ as an efficient hydrogen evolution catalyst can also improve the efficiency of photocurrent used to prepare hydrogen in electrolytic water.

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