In this work, explicitly pyro-catalytic performance is observed in sol-gel-synthesized ferroelectric Bi_0.5Na_0.5TiO₃ lead-free nanomaterials, and its application for dye wastewater purification is also actualized under temperature fluctuations varying from 23 °C to 63 °C. The decomposition ratios of the pyro-catalytic Bi_0.5Na_0.5TiO₃ nanomaterials on Rhodamine B, methyl blue and methyl orange can reach 96.75%, 98.35% and 19.97%, respectively. In the pyro-catalytic process, the probed active species such as hydroxyl radicals, superoxide radicals and holes play an extremely important role in decomposing dye molecules. The ferroelectric Bi_0.5Na_0.5TiO₃ lead-free nanomaterials will have an excellent prospect for dye wastewater purification due to its explicit pyro-catalysis.

All-inorganic perovskite solar cells suffer from low performance due to unsatisfactory carrier transport and light harvesting efficiency. Semiconductor nanopillar arrays can reduce light reflection loss and suppress exciton recombination dynamics in optoelectronic devices. In all-inorganic perovskite solar cells, few studies employing TiO₂ nanopillar arrays (TiO₂ NaPAs) have been reported to improve the device performance. Herein, well-arranged TiO₂ NaPAs are chosen to enhance the interfacial contact between perovskite and electron transporting layers for improving the carrier transport. Notably, TiO₂ NaPAs can be directly fabricated on rigid/flexible substrates at roughly room temperature by unique glancing angle deposition, which is more available than high-temperature hydrothermal/solvothermal methods. By embedding TiO₂ NaPAs into chemical processable CsPbI₂Br layers, continuous and intimate films are readily formed, guaranteeing large physical contact for facilitating more effective electron injection and charge separation. The vertically grown TiO₂ NaPAs also provide a straightforward electron transporting path to electrodes. In addition, TiO₂ NaPAs can guide the incident light and enhance the light-harvesting ability of CsPbI₂Br films. As a result, the solar cell with TiO₂ NaPAs displays a power conversion efficiency of 11.35% higher than planar control of 10.04%, and exhibits better long-term thermal stability. This strategy provides an opportunity by constructing direct interfacial regulation towards the performance improvement of inorganic perovskite solar cells.

Pyroelectric materials have the ability to convert the environmental cold–hot thermal energy such as day–night temperature alternation into electrical energy. The novel pyro-catalysis technology can be designed and realized on the basis of the product coupling between pyroelectric and electrochemical redox effects, which is helpful for the actual dye decomposition. The organic two-dimensional (2D) graphic carbon nitride (g-C₃N₄), as an analogue of graphite, has attracted considerable interest in the field of material science; however, its pyroelectric effect has rarely been reported. In this work, the remarkable pyro-catalytic performance was achieved in the 2D organic g-C₃N₄ nanosheet catalyst materials under the continuous room-temperature cold–hot thermal cycling excitation from 25 °C to 60 °C. The pyro-catalytic RhB dye decoloration efficiency of the 2D organic g-C₃N₄ can reach ~92.6%. Active species such as the superoxide radicals and hydroxyl radicals are observed as the intermediate products in the pyro-catalysis process of the 2D organic g-C₃N₄ nanosheets. The pyro-catalysis of the 2D organic g-C₃N₄ nanosheets provides efficient technology for wastewater treatment applications, utilizing the ambient cold–hot alternation temperature variations in future.

Piezoelectric materials with high piezoelectric coefficients often exhibit low carrier concentrations, which hinders the generation of free charges for piezocatalytic processes. To address this, defect engineering has emerged as a promising approach to adjust the electronic structure and enhance the carrier concentration of piezocatalytic materials. However, the introduction of defects can negatively affect the piezoelectric performance by increasing charge screening and reducing domain wall mobility. In this work, we demonstrate that a high carrier concentration can be achieved without compromising the piezoelectric properties, by applying an external electric field to enhance polarization and rearrange oxygen defect dipoles. This poling process significantly improves both piezoelectric and piezocatalytic properties. Specifically, the effective piezoelectric coefficient of a polarised, oxygen-deficient Bi₂WO_6-x material increased from d^*₃₃ ~ 4.79 pm V^‒1 to d^*₃₃ ~ 39.89 pm V^‒1. Moreover, its carrier concentration remained high, approaching N_d ~ 7.39×10²⁰cm^‒3, when subjected to ultrasonic vibrations. As a result of the high piezoelectric activity and carrier concentration, the piezocatalytic hydrogen production efficiency (per unit power) attained ~3.49 μmol g⁻¹ h⁻¹ W⁻¹. This work enables the design of efficient and energy-saving piezocatalytic materials, providing a significant step forward for hydrogen production via piezocatalytic water splitting.