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 TiO 2 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 H 2 O 2, which is subsequently decomposed on Pt to produce periodic O 2 nanobubbles that transduce catalytic activity into well-defined ionic current oscillations. Quantitative kinetic descriptors, including the oscillation frequency, dwell time (τ off ), and event interval time (τ on ), are extracted with high reproducibility. Under 532 nm excitation, the localized surface plasmon resonance (LSPR) of Au induces hot-electron injection into TiO 2, promoting charge separation and accelerating Pt-catalyzed H 2 O 2 decomposition. This coupling system enhances the O 2 generation rate while reducing both τ off and τ on . 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.