Amplifying Electron Sink Effect and Piezoelectric Polarization in Size-Minimized Nitrogen-Rich Carbon Nitride Nanosheets for Boosting H2O2 Piezo-Photosynthesis under Pure Water

Abstract Piezo-photocatalysis offers a promising technology for H2O2 production, yet its practicability is limited by insufficient charge separation, inert reaction sites, and inadequate polarization fields. Herein, we present a size-minimized nitrogen-rich carbon nitride, engineered with cyano vacancies and intercalated K+/Na+ ions. In this system, cyano vacancies function as strong electron-withdrawing sites to accelerate charge separation, while K+/Na+ ions act as efficient electron traps that suppress charge recombination. Moreover, the size-minimized nanosheet morphology further intensifies the piezoelectric polarization. This synergy amplifies the electron sink effect and piezoelectric polarization, establishing a robust built-in electric field (BIEF), which drives directional charge migration and strengthens the adsorption and activation of O2 and H2O. Under pure water conditions, the optimized catalyst exhibits an impressive piezo-photocatalytic H2O2 production rate of 7432 μmol g–1 h–1 and a high apparent quantum yield of 5.3% at 420 nm. Moreover, a solar-to-chemical conversion efficiency of 0.84% is also achieved under pure photocatalysis. This work demonstrates a synergistic strategy for amplifying electron sink effects in polar semiconductors via the combined engineering of vacancies, interlayer ions, and size, providing critical insights into the design of efficient piezo-photocatalysts for artificial H2O2 synthesis.