Owing to their remarkable success in photocatalytic applications, multiferroic BiFeO₃ and its derivatives have gained a highly promising position as electrode materials for future developments of efficient catalysts. In addition to their appropriate band gaps, these materials exhibit inherent intrinsic polarizations enabling efficient charge carrier separation and their high mobility without the need for additional co-catalysts. Here, we review the existing strategies for enhancing the photocatalytic performances of BiFeO₃-based materials and we describe the physico-chemical properties at the origin of their exceptional photocatalytic behavior. A special focus is paid to the degradation of organic pollutants and water splitting, both driven through photocatalysis to unveil the correlation between BiFeO₃ size, substitution, and doping on the one hand and the photocatalytic performances on the other hand. Finally, we provide practical recommendations for future developments of high-performing BiFeO₃-based electrodes.

We report on the fabrication of sub-20 nm BiFeO₃ (BFO) nanoparticles using a solid-state approach and preferential leching process. The nanoparticles were subsequently used to deposit, through spray pyrolysis, BFO thin films in a rhombohedral (R3c) crystallographic structure. Then, systematic investigations of the optical and the photocatalytic properties were conducted to determine the effects of the particles size, the microstructure and the increased surface area on their catalytic performances. Especially, improved optical properties were observed, with an optical bandgap energy of 2.20 eV compared to reported 2.7 eV for the bulk system. In addition, high optical absorption was obtained in the UV–visible light region reaching up to 90% at 400 nm. The photoelectrochemical measurements revealed a high photocurrent density under visible light irradiation. Besides, density functional theory calculations were performed on both bulk and thin film BFO structures, revealing an interesting comparison of the electronic, magnetic, ferroelectric and optical properties for bulk and thin film BFO systems. Both theoretical and experimental findings show that the alignment of the band edges of BFO thin film is coherent with good photocatalytic water splitting potential, making them desirable photoanode materials.

We report on the investigation of graphitic carbon nitride (g-C₃N₄) for carbon dioxide (CO₂) sensor applications. g-C₃N₄ is prepared by the thermal polycondensation of thiourea and sprayed onto a substrate with interdigitated electrodes. The resulting sensor device exhibited a high sensitivity to CO₂ molecules of ~200 ppm, a high responsivity of ~730 ms at 40 °C and a full recovery time of 36 s. Furthermore, a set of various characterization measurements demonstrated the excellent stability of both the g-C₃N₄ nanosheets and the fabricated gas sensor device. Meanwhile, density functional theory (DFT) calculations for the bulk and monolayer models, based on tri-s-triazine, revealed the optoelectronic properties of g-C₃N₄ and the interaction energy with CO₂, which is evaluated at −0.59 eV. This value indicates the very good affinity of g-C₃N₄ nanosheets to CO₂ molecules. Our findings shed light on the potential for g-C₃N₄ to be used for the development of high-performing gas sensor devices.

Aiming to improve the photocatalytic properties of transition metal perovskites to be used as robust photoanodes, [LaFeO₃]_1−x/[SrTiO₃]_x nanocomposites (LFO_1−x/STO_x) are considered. This hybrid structure combines good semiconducting properties and an interesting intrinsic remanent polarization. All the studied samples were fabricated using a solid-state method followed by high-energy ball milling, and they were subsequently deposited by spray coating. The synthesized compounds were demonstrated to possess orthorhombic (Pnma) and cubic (Pm$\overline{3}$m) structures for LFO and STO, respectively, with an average grain size of 55–70 nm. The LFO_1−x/STO_x nanocomposites appeared to exhibit high visible light absorption, corresponding to band gaps of 2.17–3.21 eV. Our findings show that LFO_0.5/STO_0.5 is the optimized heterostructure; it achieved a high photocurrent density of 11 μA/cm² at 1.23 V bias vs. RHE and an applied bias photo-to-current efficiency of 4.1 × 10⁻³% at 0.76 V vs. RHE, as demonstrated by the photoelectrochemical measurements. These results underline the role of the two phases intermixing LFO and STO at the appropriate content to yield a high-performing photoanode ascribed to efficient charge separation and transfer. This suggests that LFO_0.5/STO_0.5 could be a potential candidate for the development of efficient photoanodes for hydrogen generation via photoelectrocatalytic water splitting.

The present study investigates the effect of manganese incorporation on the structural, dielectric, and waste bioconversion of LiTaO₃ ferroelectric material. Conventional solid-state synthesis techniques were utilized to produce powder samples, which were subsequently analyzed using room-temperature X-ray diffraction (XRD) for phase identification. The analysis revealed that the material forms a continuous solid solution within the composition range of 0 to 25 mol% of manganese (Mn), exhibiting R3c-Rombohedral symmetry. Thermal investigations of Raman spectra permitted approaching the ferroelectric–paraelectric phase transition, and dielectric measurements were performed in all investigated samples. The results show that the temperature of ferroelectric-paraelectric phase transition (Tc) decreased with the increasing Mn content. Optical properties of the prepared materials were also measured and tested as photocathodes for microbial fuel cells (MFCs), showing promising performance for x = 0.10, which exceeds values found with other dopants.