Charge carrier dynamics of Earth abundant co-catalyst (Ni) modified nanorod arrays for enhanced water splitting

Abstract

The vertically oriented Ni (Ni-0) decorated hematite nanorod array have been synthesized. The optimal Ni loading enhances photocurrent density > 4 folds at 1.23 V vs RHE and lowers the overpotential for driving the water oxidation, by similar to 70 mV. The Ni decorated hematite photoelectrode shows a longer decay time (similar to 195 ps) and higher Stern-Volmer constant (5.25 M-1) than that of bare hematite photoelectrode (similar to 156 ps and 3.89 M-1, respectively), implying an efficient charge separation and transfer across the hematite nanorod-Ni nanocrystal heterointerface. Such drastic improvement in the activity is due to the unified effects of enhanced charge separation and charge carrier densities, faster charge transfer kinetics, decreased width of depletion layer, and enhanced band bending - lead by the unison of the nanorod arrays morphology and Ni modification. These results suggest potential candidature of Earth abundant metallic Ni as a co-catalysts (-alternative to noble metals) for designing new photocatalysts.