Structure-Activity Relationship in a Cobalt Aluminate Nanoparticle Cocatalyst with a Graphitic Carbon Nitride Photocatalyst for Visible-Light Water Oxidation

Development of a visible-light-driven water oxidation system utilizing a photocatalyst that consists only of earth-abundant elements is a challenge in artificial photosynthesis. Here the structure of nanoparticulate cobalt aluminate spinel (CoAl2O4) dispersed on a graphitic carbon nitride (g-C3N4) photocatalyst was studied by electron microscopy and X-ray absorption fine-structure spectroscopy. The CoAl(2)O(4)nanoparticle, which is a good cocatalyst for visible-light water oxidation on the g-C(3)N(4)photocatalyst, was loaded onto the photocatalyst by a reverse micelle method using Co(NO3)(2) center dot 6H(2)O and Al(NO)(3) center dot 9H(2)O as precursors, followed by heating at elevated temperatures in air. The O(2)evolution activity was enhanced with increasing the heating temperature, reaching a plateau at 573-673 K, beyond which it decreased. Physicochemical analyses indicated that the formation of CoAl(2)O(4)spinel nanoparticles with a minimal extent of aggregation was the key factor to obtain high water oxidation activity.