A promising p-type Co-ZnFe2O4 nanorod film as a photocathode for photoelectrochemical water splitting.

A p-type Co-ZnFe2O4 film with a one-dimensional (1D) rod-like morphology is fabricated for the first time on fluorine-doped tin oxide (FTO) through a hydrothermal reaction and sintering treatment. The p-type Co-ZnFe2O4 is obtained by doping Co ions into n-type ZnFe2O4, in which Zn sites are substituted by Co. Compared with the n-type ZnFe2O4, the light absorption edge of Co-ZnFe2O4 is clearly shifted from 589 to 624 nm, and the positions of the valence/conduction band of Co-ZnFe2O4 meet the thermodynamic requirements for water splitting. The photocurrent density of p-type Co-ZnFe2O4 is -0.22 mA cm-2 at 0 V vs. the reversible hydrogen electrode (RHE), which is enhanced 7.33-times vs. that of n-type ZnFe2O4 (-0.03 mA cm-2 at 0 V vs. RHE). This work provides useful insights into tuning the p-n character of semiconductors to realize efficient photoelectrochemical (PEC) water splitting.