| 内容提要: |
Photoelectrochemical (PEC) water splitting for hydrogen production is a promising route to alleviate the energy crisis and reduce environmental impact. Particularly, hematite (α-Fe2O3) has been extensively investigated as a promising candidate for PEC water oxidation due to its chemical stability, suitable band gap (ca. 2.1 eV) and abundance. However, poor conductivity, rapid electron-hole recombination, short hole diffusion lengths (2-4 nm) and sluggish oxygen-evolution kinetics have greatly limited its practical application.
Many efforts have focused on the reduction of bulk or surface recombination to promote the PEC activity of hematite. However, even though the suppression of substrate/hematite interfacial recombination is of equal importance, this topic has been less intensively investigated. Although the interfacial recombination has been effectively reduced, the doping effect of the dopant source from the interlayer should be well investigated and the thickness of the interlayer should be precisely controlled as well. We have designed and fabricated a hematite photoanode with an ultrathin TiO2 interlayer for PEC water oxidation. The TiO2 interlayer was conformally coated on the FTO substrate by atomic layer deposition, which was expected to suppress the FTO/hematite interfacial recombination, and provide Ti4+ dopants for increased charge density in the hematite. Furthermore, three dimensional hierarchical branches were fabricated on the hematite nanorods for increased surface areas. A photocurrent of about 2.5 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (vs. RHE) under air mass 1.5G illumination was achieved. Finally, a thin layer of an iron oxide hydroxide cocatalyst was introduced to accelerate the oxygen evolution reaction of the branched hematite photoanode, generating a photocurrent of approximately 3.1 mA cm-2 at 1.23 V vs. RHE. |