Photocatalytic hydrogen evolution of nanoporous CoFe2O4 and NiFe2O4 for water splitting

Abstract

The spinels CoFe2O4 and NiFe2O4 of nanoporous photocatalysts were prepared by dealloying and calcination. The photocatalytic performance for the hydrogen generation rate via water splitting was measured. The results revealed that CoFe2O4 exhibits a sheet-like nanoporous structure and that abundant mesopores are distributed in the nanosheets. NiFe2O4 shows a typical pore-ligament structure. The measurements show that hydrogen generation is exhibited by both oxides because the bandgap of CoFe2O4 and NiFe2O4 is higher than the water oxidization potential. The hydrogen generation rate is approximately 0.088 mmol h−1g−1 for CoFe2O4 and 0.026 mmol h−1g−1 for NiFe2O4 when the TEOA (10 vol%) sacrificial agent is adopted. This performance is significantly higher than that of methanol as the scavenger because TEOA increases the pH value of the solution, changes the negative shift in the conduction band energy level and improves the electron transport efficiency. The higher performance of CoFe2O4 is attributed to its larger specific surface area, ample unimpeded penetration diffusion paths and higher electron transfer rate.