Dynamic Response Spectroscopy: an Emergentist Framework for Multi-Timescale Electrode-Electrolyte Interfacial Dynamics

The interfaces that govern electrocatalytic reactivity exhibit complex, often coupled, multi-timescale behavior arising from the dynamic organization of ions, solvent molecules, and adsorbates. Regions referred to in classical models as the Stern or diffuse double layers are, in practice, neither static nor ideally defined backgrounds, but active, dynamic contributors to catalytic function. Nevertheless, most electrochemical and spectroscopic probes rely on assumptions of linearity or time-invariance, (implicitly) limiting their ability to resolve such intricacies. In this Perspective, we formalize and expand on Dynamic Response Spectroscopy (DRS), a framework that leverages temporally structured electrochemical perturbations and time-resolved spectroscopic detection to disentangle overlapping, and potentially coupled, nonlinear interfacial dynamics, including those that are non-Faradaic. We introduce a generalized simulation approach to model spectrotemporal responses to modulation, enabling systematic evaluation of component (elementary reaction, process) retrievability across varying coupling topologies and kinetic regimes. We illustrate the capabilities of DRS using both synthetic systems and experimental operando ATR-SEIRAS measurements during CO2 electroreduction on copper. The results demonstrate how DRS can uncover solvent dynamics, charging delays, and memory effects that elude current-only, or single frequency or modality analyses. Rather than imposing predefined mechanistic assumptions, DRS allows the system’s natural dynamical structure to emerge. We discuss the conceptual implications and practical considerations for implementing DRS across diverse catalytic systems. By acknowledging time-domain complexity, DRS can offer a new axis of mechanistic insight into the complex, emergent behaviors that shape catalytic performance.