Study of Copper Ferrite as a Novel Photocathode for Water Reduction: Improving Its Photoactivity by Electrochemical Pretreatment

Studies on water-splitting p-type oxide electrodes based on nontoxic earth-abundant elements are scarce. Herein, the behavior of electrodes composed of CuFe2O4 nanoparticles 30 nm in size is presented. The as-prepared CuFe2O4 nanoporous electrodes exhibit small anodic photocurrents in 0.1 m NaOH. However, an electrochemical pretreatment consisting in the application of sufficiently positive potentials leads to p-type behavior with a photocurrent onset as high as 1.1 V versus the reversible hydrogen electrode, which is among the most positive values reported for an oxide absorbing visible light (band gap of 2.1 eV). This photocurrent is partly due to H2 evolution, but there are also signs of photoreduction of the material. Although the photocurrents are modest, these results point to the possibility of using CuFe2O4 as a photocathode material in water-splitting devices. Furthermore, the strategy employed for the enhancement in the CuFe2O4 photoactivity could be extended to other photocathode materials.Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through projects MAT2015-71727-R, MAT2012-37676 (Fondos FEDER), and PRI-PIBIN-2011-0816 is gratefully acknowledged