Dynamic Response Spectroscopy: An Emergentist Framework for Multi-Timescale Catalytic Interfacial Dynamics

Abstract

The interfaces that govern catalytic reactivity exhibit complex, often coupled, multi-timescale behavior arising from the dynamic organization of ions, solvent molecules, and adsorbates. This complexity is especially pronounced in electrochemical systems where classical models describing 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 perturbations and time-resolved spectroscopic detection to disentangle overlapping, and potentially coupled, nonlinear interfacial dynamics, including non-Faradaic processes and other dynamics not directly reflected in product turnover. While we focus on electrochemical systems as our primary example, the DRS framework is in principle applicable to all (catalytic) systems exhibiting complex interfacial dynamics. We introduce a generalized simulation approach to model spectrotemporal responses to modulation, enabling systematic evaluation of component (elementary reaction and process) retrievability across varying coupling topologies and kinetic regimes. We illustrate the capabilities of DRS using both synthetic systems and, as a case study, 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, 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 catalytic systems. By acknowledging time-domain complexity, DRS offers an alternative axis of mechanistic insight into the emergent behaviors that govern catalytic activity, selectivity, and stability.