Nano Tungsten Trioxide Film for Hydrogen Production

PEC technology is based on solar energy and water, both of which are renewable. PEC technology has no by-products and will not bring pollution to the environment. Moreover, PEC technology can be applied in small scale and developed in large scale. Therefore, this technology is the most attractive way to produce hydrogen directly by solar energy.

Compared with traditional titanium dioxide and zinc oxide semiconductor materials, tungsten trioxide has the advantages of narrow band gap (2.5ev), absorption of visible light with wavelength greater than 500nm in the solar spectrum, low price, good chemical stability, non-toxic, no light corrosion, etc. it is a good semiconductor material for solar energy applications.

It can be used in the hydrogen production technology of solar photoelectrochemical cell. The preparation method of the nano tungsten trioxide film includes the following processes:

1.Preparation of precursor: dissolve a proper amount of water-soluble polytungstate in the secondary deionized water, add a certain amount of dispersant and modifier, mix continuously with the magnetic stirrer, and then stand at a constant temperature to obtain the precursor. The function of dispersant is to form a large number of interlaced network structure, which is not easy to produce cracks in the process of drying and high-temperature crystallization; while the function of modifier improves the stability of the precursor, in addition, in the process of film growth under high-temperature conditions, it can prevent the agglomeration of nano tungsten trioxide particles and lead to the film falling off.

2.Coating method: coating on the substrate to be coated by dip pull or spin coating, and drying at a certain temperature. The substrate to be coated shall be cleaned first. The base material is one of aluminum, stainless steel, glass, graphite and silicon.

3. Baking method: after the substrate coating is dried, it is placed in the muffle furnace with programmable temperature control for high temperature baking. The nano-sized tungsten trioxide films were obtained by heating rate of 1-10 ℃ / min, calcination temperature of 350-600 ℃ and heat treatment of 2-5h.

The nano-sized tungsten trioxide film prepared by this process has good photoelectric properties: the current density of 3.9ma/cm2 under the condition of 60MW / cm2 light intensity and 1.5V bias voltage, which is 2-3 times higher than that of WO3 prepared by the process of dissolving tungsten powder in hydrogen peroxide.

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