Photoactive Brownmillerite Multiferroic KBiFe₂O₅ and Its Potential Application in Sunlight-Driven Photocatalysis

Abstract

KBiFe 2 O 5 (KBFO) is an upcoming promising brownmillerite-structured multiferroic photoactive material for next-generation photovoltaic and photocatalytic applications. In the present work, KBFO has been developed using multistep thermal treatment method to reduce the volatility of constituent elements and improve the stability of compound. The band gap of KBFO (found to be ∼1.68 eV) extends to the near-infrared region compared to traditional perovskite-structured multiferroics. The magnetic and dielectric transitions occur in the same temperature range (740 K–800 K), reflecting the existence of magneto-dielectric effect in the as-synthesized sample. It also shows promising photocatalytic activity by degrading organic effluents under natural sunlight compared to regular perovskite BiFeO 3 photocatalyst (operating under visible light). A new application of brownmillerite multiferroic KBFO photocatalyst in environmental and energy applications has been explored by integrating the structural, optical, magnetic, and dielectric properties of the same.

Nitrogen Incorporated Photoactive Brownmillerite Ca2Fe2O5 for Energy and Environmental Applications

“…4(b)). The positions of Fe 2p 3/2 and Fe 2p 1/2 spin orbits at 711.62 eV and 724.40 eV respectively for CFO confirms the existence of Fe in Fe 3+ valence state 36 . A small shift in Fe 2p towards lower binding energy in CFO-N arises due to the replacement of O in Fe-O sites by N. Since N has lower electronegativity as compared to O, it leads to lower binding energy of Fe 2p in CFO-N by forming Fe-N x sites 37 .…”

“…Figure 10 shows a possible MB photodegradation pathway in the presence of catalyst. During the photocatalytic degradation process, active species such as holes(h + ) and hydroxyl radicals ( · OH) are generated which are responsible for mineralization of MB into unstable organic byproducts Cl − , NO 3 − , SO 4 2− , CO 2 , and H 2 O 36,43 . MB degradation process is initiated by active species breaking the S-Cl bonds and then Cl − ions being separated from MB core structure.…”

Structural, optical, and magnetic properties of KBiFe2O5 synthesized by a sol‐gel method using PVP as additive

“…On the other hand, the KBFO 3 and KBFO 4 samples that have more amount of a second phase (like sample KBFO 5) have magnetic properties with characteristics of a weak ferromagnetic material. This difference may be related to the weakness of the Bi‐O bond 12 …”

g-C3N4/Ca2Fe2O5 heterostructures for enhanced photocatalytic degradation of organic effluents under sunlight

“…3 (b&e). The peaks arising due to spin orbits split namely Fe 2p 3/2 and Fe 2p 1/2 , are further deconvoluted into two peaks, corresponding to octahedral (FeO 6 ) and tetrahedral (FeO 4 ) coordination peaks of Fe 40 , 41 . Brownmillerite Ca 2 Fe 2 O 5 consists of alternative layers of FeO 6 octahedra and FeO 4 tetrahedra as shown in Fig.…”