DES-guided engineering of N-doped carbon for mussel-inspired, oxygen-vacancy-rich CeO₂ nanozymes toward H₂O₂ sensing

Rational design of highly dispersed CeO₂ nanozymes with abundant oxygen vacancies is critical for achieving efficient and sensitive H₂O₂ detection. Herein, we report a deep eutectic solvent (DES)-guided engineering strategy to construct an N-doped carbon (NC) framework integrated with mussel-inspired, uniformly dispersed CeO₂ nanoparticles. The DES acts both as a green C/N source and a self-templating medium, regulating heteroatom distribution and graphitization degree to yield a conductive carbon scaffold. Dopamine undergoes oxidative self-polymerization under mild alkaline conditions, and its catechol–amine functionalities strongly chelate Ce³⁺ ions, directing homogeneous nucleation and suppressing nanoparticle aggregation. This molecularly engineered architecture produces an oxygen-vacancy-rich interface enriched with redox-active Ce³⁺/Ce⁴⁺ sites, enabling rapid electron transfer and accelerated H₂O₂ redox kinetics. The optimized CeO₂/NC electrode delivers a diffusion-controlled amperometric response with dual linear ranges (0.05–60 and 60–300 μM), a low detection limit of 0.036 μM, and sensitivities of 94.8 and 49.3 mA M^-1 cm^-2, respectively, surpassing most reported CeO₂-based sensors. Furthermore, the sensor exhibits excellent selectivity and retains 89 % of its initial response after prolonged operation. This work provides a scalable, eco-friendly pathway for constructing bioinspired, oxygen-vacancy-rich nanozymes, offering broad applicability in advanced electrocatalytic sensing platforms.