Evaluating Charge Carrier Transport and Surface States in CuFeO2 Photocathodes

Abstract

Interest in delafossite (CuFeO2) as a candidate p-type photocathode for photoelectrochemical (PEC) solar fuel production has recently been increasing, mainly due to its excellent stability in aqueous environments and favorable light absorption properties. However, its PEC performance has remained poor for reasons that have not yet been specifically determined. Herein, we report a detailed investigation on sol–gel-processed CuFeO2 with a range of spectroscopic, PEC, and microscopy techniques aimed at unraveling the material properties governing photogenerated charge carrier harvesting in this v. An analysis of the bulk transport properties using microwave conductivity measurements reveals a good charge carrier mobility (0.2 cm2 V–1 s–1) and a relatively long lifetime (200 ns) for photogenerated charge carriers. Conversely, systematic PEC measurements with varied redox systems reveal the existence of a high density of surface states (1014 cm–2) positioned 0.35 eV above the conduction band, inducing Fermi le...