Experimental teaching in materials chemistry is central to developing students’ research literacy and practical competence. In the context of emerging engineering education, conventional laboratory instruction exhibits three major limitations: fragmentation of synthesis, characterization, and performance evaluation (impeding systematic understanding of structure–property relationships); outdated content with insufficient coverage of advanced functional materials; and overly prescriptive protocols that constrain independent inquiry and innovation. To address these issues, this study adopts the visible-light-responsive material BiVO₄ as a model system and develops a micro-project-driven teaching framework that integrates discrete experimental components into a coherent, progressive task chain.

Because the crystal phase of BiVO₄ is highly sensitive to hydrothermal temperature, a teaching model based on single-variable open inquiry and parallel multigroup collaboration was established. Low-toxicity precursors and the biodegradable surfactant sodium dodecylbenzene sulfonate (SDBS) were employed, with hydrothermal temperatures maintained below 200 ℃. A standardized waste-management protocol ensured safety and reproducibility. Thirty students were divided into six groups, implementing intragroup role rotation and a group-leader responsibility system. Instructors coordinated progress through structured briefings and resource allocation, enabling parallel execution and cross-validation of results. Hydrothermal temperature was defined as the sole independent variable, while precursor concentration, pH, and reaction time were strictly controlled. Students conducted broad-range screening followed by refined sampling near the phase-transition region, yielding 19 experimental conditions at eight temperatures. Four progressive inquiry modules (color variation, bandgap evolution, the role of SDBS, and the adsorption–photocatalysis relationship) were embedded throughout synthesis, characterization, and performance evaluation. Instruction was limited to targeted questioning at critical stages to facilitate students’ autonomous construction of structure–property relationships. A comprehensive 100-point evaluation system emphasized formative assessment (30%), integrated peer review, instructor observation, written reports, and oral defense.

The framework effectively transformed fragmented experimental steps into a continuous investigative process. Through multi-modal characterization (XRD, SEM, UV–Vis, FTIR, and photocatalytic degradation tests), students independently constructed structure–property relationships, with the majority of students demonstrating this capability. The approach requires only standard laboratory infrastructure and low-toxicity reagents, with high intergroup consistency.

A micro-project-based experimental teaching model centered on BiVO₄ and characterized by single-variable open inquiry, parallel group collaboration, and progressive problem-driven learning was successfully developed. By systematically integrating synthesis, characterization, and performance evaluation and guiding students through structured inquiry pathways, the approach overcomes key limitations of traditional laboratory teaching. With advantages such as safety, low cost, high reproducibility, and scalability, this model provides a practical and transferable framework for advancing materials chemistry laboratory education under the emerging engineering education paradigm.

Piezocatalysis is a catalytic effect driven by the stress-induced electricity of piezoelectric crystallites. Utilizing the piezoelectric effect, piezoelectric catalysis technology can induce the generation of piezoelectric potential in piezoelectric materials through mechanical energy to drive redox reactions, offering promising applications in alleviating energy crises and managing environmental pollution. Despite significant progress in piezoelectric catalysis with piezoelectric materials, suboptimal piezoelectric catalytic performance remains an issue owing to factors such as low separation efficiency of charge carriers and the limited active sites available for surface reactions. To further enhance the piezoelectric catalytic performance, this study employs an optimized approach to fabricate Bi₂Fe₄O₉nanosheets. The catalytic degradation performance of these nanosheets was investigated using rhodamine B simulated wastewater in an ultrasound-induced Bi₂Fe₄O₉ nanosheet piezoelectric catalysis system.

Bi₂Fe₄O₉ nanosheets were synthesized using a hydrothermal method optimized with bismuth nitrate pentahydrate (Bi (NO₃)₃·5H₂O) and iron nitrate pentahydrate (Fe (NO₃)₃·9H₂O) as raw materials. X-ray diffraction (XRD) analysis using Cu Kα radiation (λ=1.5406 Å) was used to characterize the crystal structure of the Bi₂Fe₄O₉ sample. The morphology and composition were characterized using field emission transmission electron microscopy. The elemental composition and chemical states of the catalysts were analyzed using X-ray photoelectron spectroscopy with data obtained processed through XPSPEAK software. The piezoelectric properties of the Bi₂Fe₄O₉ nanosheets were evaluated through force-phase microscopy and transient current measurements conducted at an electrochemical workstation. The piezocatalytic performance of Bi₂Fe₄O₉ nanosheets was evaluated by ultrasonic activation of Bi₂Fe₄O₉ nanosheets to catalyze persulfate (US/Bi₂Fe₄O₉/S₂O₈²⁻) for rhodamine B (RhB) degradation. Additionally, control experiments (US/ S₂O₈²⁻ and Bi₂Fe₄O₉/S₂O₈²⁻) were also conducted under the same reaction conditions.

SEM results indicated that the Bi₂Fe₄O₉ samples prepared by the optimized hydrothermal method had a smooth surface, single dispersion, and an average size of 910 × 82 nm in thin flake-like structures. The high peak height of the (001) crystal plane diffraction suggested that the optimized hydrothermal method promotes exposure of the (001) crystal plane, facilitating electron and hole transfer to the crystal surface and preventing their recombination. Elemental mapping confirmed the uniform distribution of Bi, Fe, and O within the Bi₂Fe₄O₉ nanosheets. Transient current measurements showed a significant increase when the ultrasonic device was activated, which instantaneously decreased once the ultrasonic device was turned off. The ultrasound-cavitation-induced Bi₂Fe₄O₉ nanosheets piezoelectric catalysis S₂O₈²⁻ system (US/Bi₂Fe₄O₉/S₂O₈²⁻) achieved a RhB removal rate of 97.8%, while the ultrasound-activated S₂O₈²⁻ system (US/S₂O₈²⁻) and the Bi₂Fe₄O₉-activated S₂O₈²⁻ system (Bi₂Fe₄O₉/S₂O₈²⁻) achieved an RhB removal rate of 32.5% and 72.3%, respectively. This demonstrates a significant synergistic promotion effect of the multi-field coupling system combining ultrasound activation piezoelectric and piezoelectric catalysis.

Bi₂Fe₄O₉ nanosheets prepared using the optimized hydrothermal method exhibited enhanced piezoelectric properties. The optimized hydrothermal method fabricates Bi₂Fe₄O₉ nanosheets of high purity, uniform size, and good dispersibility. Besides, elements of Bi, Fe and O are uniformly distributed across the Bi₂Fe₄O₉ nanosheets. Piezoelectric property analysis shows that Bi₂Fe₄O₉ nanosheets demonstrate significant piezoelectric properties, while the piezoelectric potential induced by ultrasonic cavitation triggers redox reactions. Compared with US/S₂O₈²⁻orBi₂Fe₄O₉/S₂O₈²⁻, the multi-field coupling system of ultrasonic activation piezoelectricity and piezoelectric catalysis (US/Bi₂Fe₄O₉/S₂O₈²⁻) has a significant synergistic enhancement effect. The findings provide new insights into the development of piezocatalysts and the mechanism of piezocatalytic degradation.