Photocatalytic water splitting

Photocatalytic water splitting is an artificial photosynthesis process with photocatalysis in a photoelectrochemical cell used for the dissociation of water into its constituent parts, hydrogen (H2) and oxygen (O2), using either artificial or natural light. Theoretically, only solar energy (photons), water, and a catalyst are needed. This topic is the focus of much research, but thus far no technology has been commercialized.When H2O is split into O2 and H2, the stoichiometric ratio of its products is 2:1:Photocatalysts must confirm to several key principles in order to be considered effective at water splitting. A key principle is that H2 and O2 evolution should occur in a stoichiometric 2:1 ratio; significant deviation could be due to a flaw in the experimental setup and/or a side reaction, both of which do not indicate a reliable photocatalyst for water splitting. The prime measure of photocatalyst effectiveness is quantum yield (QY), which is:Solid solutions Cd1-xZnxS with different Zn concentration (0.2 < x < 0.35) has been investigated in the production of hydrogen from aqueous solutions containing SO 3 2 − / S 2 − {displaystyle {ce {SO3^2-}}/{ce {S^2-}}}   as sacrificial reagents under visible light. Textural, structural and surface catalyst properties were determined by N2 adsorption isotherms, UV–vis spectroscopy, SEM and XRD and related to the activity results in hydrogen production from water splitting under visible light irradiation. It was found that the crystallinity and energy band structure of the Cd1-xZnxS solid solutions depend on their Zn atomic concentration. The hydrogen production rate was found to increase gradually when the Zn concentration on photocatalysts increases from 0.2 to 0.3. Subsequent increase in the Zn fraction up to 0.35 leads to lower hydrogen production. Variation in photoactivity is analyzed in terms of changes in crystallinity, level of conduction band and light absorption ability of Cd1-xZnxS solid solutions derived from their Zn atomic concentration.