Hydrogen production using solar grade wasted silicon

• Solar grade wasted silicon was refined through centrifuge method.
• There is still few silicon carbide existed in the refined powder.
• Solar grade wasted silicon was reused to produce hydrogen via chemical or photocatalytic process.

In recent years, establishing a reliable and effective technology to recycle or recover valuable material from the spent modules or development discharges has gained worldwide recognition and popularity as an environmentally friendly way of disposing the industrial production wastes. Crystalline silicon wafer plays an important role in the photovoltaic industry, which gets wasted more than 40% in the slicing process. The challenge associated with the complete removal of silicon carbide particles from the cutting waste conquers the key point in recycling of crystalline silicon. In this article, solar grade wasted silicon was reused to produce hydrogen via chemical reaction between Si and H2O using alkali as catalyst or photocatalytic water splitting using purified Si as photocatalysts. The structure, compositional and optical properties of the wasted silicon were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible (UV-vis) spectroscopy. The morphology of wasted silicon powder was measured by scanning electron microscopic(SEM), high resolution transmission electron microscopic (HRTEM). Electronic structure of wasted silicon powder was characterized by photoluminescence spectroscopy(PL). Although subjecting to a series of chemical treatments, there is still few silicon carbide existed in the refined powder. The amount of H2 production detected (2.055 mmol) in the catalytic reaction greatly exceeds the hydrogen yield in the chemical reaction between silicon and sodium hydrate (0.2 mmol), indicating the feasibility of chemical reaction between wasted photovoltaic silicon and H2O catalyzed by alkali. The refined silicon powder displayed photocatalytic activity for hydrogen production in the presence of oxalic acid as sacrifice reagent. The study proposes methods for the utilization of industrial discharge from crystalline silicon solar cells, yielding valuable hydrogen evolution with the advantages of low energy consumption, low pollution, and easy operation.

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