Operando Electrochemical Tracking of Plasmon–Photocatalytic-Coupled Cascade Catalysis in a Confined TiO ₂ Nanopipette Reactor

Operando tracking of nanoscale catalytic dynamics is essential for elucidating transient interfacial events that dictate reaction efficiency. Here, we report a confined TiO2 nanopipette reactor integrated with Au and Pt nanozymes that enables single-entity, bubble-resolved tracking of plasmon–photocatalytic-coupled cascade catalysis. Within the nanoconfined channel, glucose oxidation on Au generates H2O2, which is subsequently decomposed on Pt to produce periodic O2 nanobubbles that transduce catalytic activity into well-defined ionic current oscillations. Quantitative kinetic descriptors, including the oscillation frequency, dwell time (τoff), and event interval time (τon), are extracted with high reproducibility. Under 532 nm excitation, the localized surface plasmon resonance (LSPR) of Au induces hot-electron injection into TiO2, promoting charge separation and accelerating Pt-catalyzed H2O2 decomposition. This coupling system enhances the O2 generation rate while reducing both τoff and τon. The nanoconfined environment enables robust catalytic detection down to 10 μM glucose, far below the macroscopic limit. Macro–micro correlated measurements further reveal synergistic regulation of the cascade kinetics by illumination and substrate concentration. This work establishes a versatile operando platform for quantifying nanoscale bubble dynamics and light-regulated cascade catalysis, offering opportunities for engineering responsive catalytic systems and next-generation microreactors.