Solar hydrogen generation from spinel ZnFe sub(2)O sub(4) photocatalyst: effect of synthesis methods

This paper investigates solar radiation-induced photocatalytic hydrogen generation using spinel ZnFe sub(2)O sub(4) (ZFO) photocatalysts fabricated using different routes, viz., solid state reaction (SSR), polymer complex (PC), microwave sintering ( mu W) and self-propagating combustion (SPC) method. The physicochemical properties of the photocatalysts like crystallinity, surface area, band gap and band energetics is studied as it influences their photochemical behavior. The study reveals a high crystallinity of the ZFO photocatalysts, those are synthesized using SSR, PC and mu W methods, where SSR method yields the larger dimension crystallites of ~53nm. The nanoparticles obtained from SPC methodology exhibit a relatively large surface area and a smaller crystallite size of around ~18nm. Monodispersed particles with comparatively large surface area are obtained in the case of PC method. ZFO obtained from mu W synthesis exhibits enhanced optical properties, thus favoring high absorption of solar photons. A relatively more negative flat band potential is displayed by the mu W samples (-0.543 vs normal hydrogen electrode) as estimated from the electrochemical measurements. Consequently, these samples yield a higher quantum yield (0.19%) for hydrogen evolution even without co-catalyst loading. On the contrary, the photocatalysts obtained by SSR and PC methods did display an enhancement in the quantum yield as compared to the mu W samples but only after Pt co-catalyst loading. * times Nanoparticle zinc ferrite photocatalysts were synthesized by four different methods * times Photocatalyst prepared by conventional synthesis/SSR and microwave showed suitable properties as flat band potential * times Microwave sintered photocatalyst showed maximum hydrogen evolution