Ab-initio investigation of a novel photocathode: bulk and surface properties of CuFeO₂

Photoelectrochemical (PEC) devices offer the possibility to convert solar radiation into chemical fuels, mimicking the natural process of photosynthesis. Recent experiments have highlighted CuFeO₂ (CFO) as a promising candidate in the role of photocathode [1, 2], yet in spite of these encouraging results, improvement in the catalytic activity and charge separation is required.
In this work, we present a theoretical characterization of CFO based on the DFT+U approach and refined with hybrid calculations. We characterized the stability of bulk CFO with respect to other iron and copper oxides in air and in an aqueous environment, coupling DFT with ab-initio thermodynamics. On this basis, we studied the formation energy of native defects of CFO. The low formation energy of a copper antisite defect could be detrimental for the PEC operations of CFO since states inside the energy gap could favour the electron-hole recombination.
Based on our thermodynamic screening we focused our investigation on two energetically relevant surfaces. We interfaced these surfaces with water and we performed ab-initio molecular dynamics simulations to determine the alignment between the band edges and the redox potentials of water.
[1] Adv. Mater. 28, 9308 (2016)
[2] Nature Rev. Mat. 1, 15010 (2016)