Phase and photoelectrochemical behavior of solution-processed Fe2O3 nanocrystals for oxidation of water under solar light

Monodispersed iron-oxide nanocrystals of controlled sizes $(5–16\mathrm{nm})$ were prepared by the thermal decomposition of iron-oleate complex to fabricate photoanode films for photoelectrochemical oxidation of water under simulated solar light. The smallest $5\mathrm{nm}$ particles were made mostly of $\gamma \text{-}{\mathrm{Fe}}_2{\mathrm{O}}_3$ , but other sizes showed mixed phases with ${\mathrm{Fe}}_3{\mathrm{O}}_4$ , whose fraction increased with size. Size-dependent photoanodic currents were also observed, showing maximum photocurrent density for $12\mathrm{nm}$ particles. The high photocurrents were attributed to the lowered electron-hole recombination rates for the nanocrystals with the sizes comparable to the hole diffusion length.