Cobalt-Phosphate modified TiO2/BiVO4 nanoarrays photoanode for efficient water splitting

Abstract Using TiO 2 nanorods as one-dimensional (1D) electron transport tunnel, BiVO 4 as light harvester, and Co-Pi (Cobalt-Phosphate) as co-catalyst, TiO 2 /BiVO 4 /Co-Pi nanorod arrays were fabricated as efficient photoanode on a FTO substrate for photoelectrochemical (PEC) water splitting cells. It was found that the monoclinic BiVO 4 nanoflakes were mainly vertically attached to the side faces of rutile TiO 2 nanorods with an average size of ∼35 nm and a selective growth direction along . By changing the electrodeposited quantity of BiVO 4 , the effect of the loading density of BiVO 4 on the PEC performance was systematically studied, and an optimum photocurrent of ∼1.86 mA cm −2 at 1.0 V RHE with an onset potential as small as 0.3 V RHE and IPCE of 26% (at 450 nm) was obtained for the TiO 2 /BiVO 4 /Co-Pi anodes. Electrochemical impedance spectroscopy showed that Co-Pi can greatly decrease the charge transfer resistance at the photoanode/electrolyte interface. Along with the band alignment of the 1D nanoarray heterostructure beneficial for the charge separation, a hydrogen production of ∼7.31 μmol cm −2  h −1 was achieved for the efficient water splitting system. Such a heterostructured 1D nanoarray configuration can be extended to other PEC water splitting systems as well to increase the number of reactive sites and absorption of solar light, and to enhance the OER kinetics.