Co-Fe layered double hydroxide decorated titanate nanowires for overall photoelectrochemical water splitting

Abstract

Photoelectrochemical water splitting is regarded as a promising technology to produce H2 as a clean energy vector. TiO2 nanowires (TNWs) as one dimensional nanostructures offer several merits including large area to volume ratio and improved electron transport properties. In this study CoFe-CO3 layered double hydroxide (LDH) was used as a photosensitizer to decorate the surface of TNWs with different weight ratios (LDH: TNWs = 0:1, 0.25:1, 0.5:1, 1:1 and LDH). TEM images indicated that the layered structure of LDH was not formed for all samples except for the 1:1. This is attributed to the partial incorporation of Co and Fe ions into the titanate structure thereby deteriorating the Co:Fe minimum ratio for layered structure formation. Adding LDH extended the absorption range of TNWs to the entire visible range and decreased the band gap to 2.57 eV. Co-Fe LDH shifted the onset potentials for both the oxygen and hydrogen evolution reactions by 220 and 330 mV respectively. At 1 V Vs Ag/AgCl, the anodic current increased by 9.4, 23.45 and 34.32 folds for the 0.25:1, 0.5:1 and 1:1 photoanodes respectively. At −1 V Vs Ag/AgCl, the cathodic current reached 0.25, 0.68, and 0.81 mA/cm2 for 0.25:1, 0.5:1 and 1:1 samples respectively.