Strain-induced local polarization field modulation and spin state alternation in atomic Ni-anchored carbon nitride for boosting piezo-photocatalysis

Piezo-photocatalysis enables solar-to-chemical conversion driven by both light and mechanical energy, yet its practical efficiency is hampered by two inherent obstacles: piezopotential shielding from excessive charge accumulation at polar edges, and spatiotemporal mismatch between dynamic carrier migration and surface catalytic sites. Herein, a series of nNi-CN piezo-photocatalysts with tunable single-atom Ni loading was synthesized via post-impregnation to tackle this critical limitation. Ni single atoms are anchored in the triangular planar cavities of carbon nitride (CN) with a well-defined Ni-N 6 coordination. The embedded Ni not only enhances the in-plane dipole moment and piezoelectric response of CN, but also induces radial local polarization fields centered at Ni sites, which redirect carrier migration pathways, shorten carrier diffusion distance, and effectively suppress piezopotential shielding by confining carriers at local active centers. More importantly, strain exerts a dual regulatory role in synchronously modulating the local polarization field intensity and the spin-state alternation of Ni sites under different strain regions. Compressive strain optimizes the Ni spin state toward a thermodynamically favorable hydrogen evolution configuration, enabling spatial alignment between electron accumulation terminals and reduction active sites and realizing dynamic spatiotemporal matching of charge supply and active-site utilization. The optimized 2Ni-CN exhibits exceptional piezo-photocatalytic water splitting performance under ultrasonic (40 kHz, 100 W) and LED illumination (36 W), achieving a H 2 production rate of 440.7 μmol·h -1 ·g -1 (23.6 times that of pristine CN) with a synergistic enhancement factor of 2.27. This study puts forward a versatile single-atom engineering strategy to suppress piezopotential shielding and resolve carrier-site spatiotemporal mismatch, paving an innovative pathway toward high-efficiency piezo-photocatalysts.