Metal Doping to Enhance the Photoelectrochemical Behavior of LaFeO₃ Photocathodes

Abstract

Abstract The development of tandem devices for water photosplitting requires the preparation of photocathodic materials based on earth‐abundant elements that show long‐term stability in aqueous electrolytes. Ternary metal oxides seem to be a viable option, among which perovskites stand out. In this context, transparent and compact LaFeO 3 thin‐film electrodes have been prepared by a sol–gel process, both undoped and doped with metals (M) such as Mg or Zn. Pristine electrodes support the development of cathodic photocurrents in 0.1 m NaOH aqueous solutions, particularly in the presence of oxygen, with an onset potential as high as 1.4 V versus the reversible hydrogen electrode. Doping with Mg or Zn leads to an important enhancement of the photocurrent, which peaks for a stoichiometry of LaFe 0.95 M 0.05 O 3 with a sixfold enhancement with respect to the pristine material. Such an improvement is attributed to an increase in both the density and mobility of the majority carriers, although a contribution of surface passivation cannot be excluded.