This review covers recent advances in understanding, designing, and exploring the defect in carbon toward energy-related applications, with the aim of referencing and guiding the large-scale and diverse applications of defect-rich carbon materials.

Creating efficient catalysts for simultaneous H ₂ O ₂ generation and pollutant degradation is vital. Piezocatalytic H ₂ O ₂ synthesis offers a promising alternative to traditional methods but faces challenges like sacrificial reagents, harsh conditions, and low activity. In this study, we introduce a cobalt-loaded ZnO (CZO) piezocatalyst that efficiently generates H ₂ O ₂ from H ₂ O and O ₂ under ultrasonic (US) treatment in ambient aqueous conditions. The catalyst demonstrates exceptional performance with ~50.9% TOC removal of phenol and in situ generation of 1.3 mM H ₂ O ₂ , significantly outperforming pure ZnO. Notably, the CZO piezocatalyst maintains its H ₂ O ₂ generation capability even after multiple cycles, showing continuous improvement (from 1.3 mM to 1.8 mM). This is attributed to the piezoelectric electrons promoting the generation of dynamic defects under US conditions, which in turn promotes the adsorption and activation of oxygen, thereby facilitating efficient H ₂ O ₂ production, as confirmed by EPR spectrometry, XPS analysis, and DFT calculations. Moreover, the CZO piezocatalysts maintain outstanding performance in pollutant degradation and H ₂ O ₂ production even after long periods of inactivity, and the deactivated catalyst due to metal ion dissolution could be rejuvenated by pH adjustment, offering a sustainable solution for wastewater purification.