A Novel Synthesis Yielding Macroporous CaFe₂O₄ Sponges for Solar Energy Conversion

Abstract

Phase‐pure and highly crystalline CaFe 2 O 4 with a sponge‐like macroporous structure is synthesized for the first time via facile solution‐based microwave reaction and subsequent short thermal treatment. The formation mechanism of the orthorhombic phase ( Pnma ) and the pore network is investigated in detail and reveals a complex formation of this p‐type semiconductor. Superconducting quantum interference device (SQUID) magnetometry and Mössbauer spectroscopy confirm the phase changes by altered magnetic properties. Furthermore, the optical and photoelectrochemical properties of the material were investigated. The material has a bandgap of 1.9 eV and sufficient band positions for water splitting. Valence‐to‐core X‐ray emission spectroscopy is used to support the band positions obtained from Mott–Schottky analysis. Photocathodes prepared from macroporous CaFe 2 O 4 generate photocurrents under illumination with light of up to 600 nm.