Hematite nanorods Co-doped with Ru cations with different valence states as high performance photoanodes for water splitting

Abstract

This work reports the synthesis and characterization of sub-10nm, porous Ru-doped α-Fe2O3 nanorods (NRs) as well as their implementation as photoanodes for water splitting. Highly photoactive Ru-doped α-Fe2O3 NR films were prepared by deposition of the ruthenium(III) acetylacetonate [Ru(acac)3]-treated presynthesized ultrathin α-FeOOH NR precursors onto FTO substrates via a doctor blading process, followed by annealing at 700°C in air. The photoelectrochemical (PEC) water splitting performance of the undoped and Ru-doped α-Fe2O3 NR photoanodes was characterized and optimized by varying the precursor molar ratio of α-FeOOH to Ru(acac)3. Significantly, under simulated 1 sun illumination, the optimized Ru-doped α-Fe2O3 NR films obtained at a Fe/Ru molar ratio of 100/5 yield a stable, record photocurrent density of ~5.7mAcm–2 and the highest incident photon to current conversion efficiencies (IPCEs) at 1.23V vs a reversible hydrogen electrode (RHE) and show an onset potential of anodic photocurrent around 0.7V vs RHE. The excellent PEC performance benefits from: (i) the simultaneously increased charge carrier concentration and mobility and (ii) charge balance provided by codoping of different valent Ru cations, resulting in a significant reduction of the defects that are supposed to serve as the recombination centers for photogenerated electrons and holes in the α-Fe2O3 lattice.