Highly Efficient Photocatalytic Z-Scheme Hydrogen Production over Oxygen-Deficient WO3–x Nanorods supported Zn0.3Cd0.7S Heterostructure (original) (raw)
The demand for clean renewable energy is increasing due to depleting fossil fuels and environmental concerns. Photocatalytic hydrogen production through water splitting is one such promising route to meet global energy demands with carbon free technology. Alternative photocatalysts avoiding noble metals are highly demanded. Herein, we fabricated heterostructure consist of oxygen-deficient WO 3-x nanorods with Zn 0.3 Cd 0.7 S nanoparticles for an efficient Z-Scheme photocatalytic system. Our as obtained heterostructure showed photocatalytic H 2 evolution rate of 352.1 μmol h −1 with apparent quantum efficiency (AQY) of 7.3% at λ = 420 nm. The photocatalytic hydrogen production reaches up to 1746.8 μmol after 5 hours process in repeatable manner. The UV-Visible diffuse reflectance spectra show strong absorption in the visible region which greatly favors the photocatalytic performance. Moreover, the efficient charge separation suggested by electrochemical impedance spectroscopy and photocurrent response curves exhibit enhancement in H 2 evolution rate. The strong interface contact between WO 3-x nanorods and Zn 0.3 Cd 0.7 S nanoparticles ascertained from HRTEM images also play an important role for the emigration of electron. Our findings provide possibilities for the design and development of new Z-scheme photocatalysts for highly efficient hydrogen production. The increasing demand for energy and depleting crude oil resources forced researchers to find alternate options for rapidly growing world population. The burning of fossil fuels also deteriorating world's climate by the emission of CO 2 and other green house gases 1. Therefore, a sustainable and clean energy source is the biggest challenge for the 21 st century. Photocatalytic hydrogen production emerges as environment friendly method since the pioneer work of Fujishima and Honda in 1972 2. Since then, a large number of photocatalysts have been synthesized for water splitting to generate hydrogen 3. However, most of catalysts either depend upon expensive noble metals as co-catalyst (Pt, Ru, and Rh) or only absorb in the ultraviolet region which accounts for only 4% of the incoming solar light. Metal oxides such as WO 3 , NiO and RuO 2 emerges as new class of photocatalyst for efficient hydrogen production 4-9. However, photocatalysts with maximum absorption in the visible region and suitable band-gap are highly desirable. Cadmium sulphide (CdS) attracts considerable attention due to its narrow band gap (2.4 eV) for photocatalytic hydrogen evolution reaction. However the rate of H 2 production over CdS is very low because of its photo-corrosion property and fast-recombination of electron-hole pair which renders its practical applications impossible 10. The use of co-catalyst or incorporation of Zn ion into CdS to form Zn 1-x Cd x S (0-1) greatly enhances the photocatalytic activity. Recently, the band-gap for Zn 1-x Cd x S has been varied to achieve maximum visible absorption and greater charge separation efficiency for water splitting 11. However, there are only few reports which suggest room temperature synthesis with excellent photocatalytic property and recyclability. Moreover, a heterostructure comprising two different photocatalysts is considered a better option compared to conventional
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