A waveguide kinetics framework for electrochemical polarization

Hydrogen electrocatalysis (HER/HOR) exhibits an anomalous, non-Nernstian pH dependence that has motivated competing mechanistic narratives yet still lacks a unified, transferable, and quantitatively predictive description across conditions. Here, we introduce a theory-neutral waveguide kinetics framework that reinterprets the polarization curve as a power-flow-like response, enabling a compact modal representation of interfacial kinetics. Without presuming any specific mechanism, the model quantitatively fits four representative polarization datasets historically explained by divergent theories. From each fit, we extract interpretable diagnostics, including a reflection amplitude and a useful-output density, that provide transferable metrics for interfacial efficiency. The framework thus establishes a computational experiment platform for mechanistic triangulation, operating-regime diagnosis, and the rational design of hydrogen electrocatalysts across the pH spectrum.

💡 Research Summary

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Hydrogen electrocatalysis, encompassing both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR), displays a strikingly non‑Nernstian dependence on pH. This anomalous behavior has spawned a multitude of competing mechanistic explanations—hydrogen‑binding energy, cation‑effects, interfacial water structuring, and others—yet none of these theories offers a unified, transferable, and quantitatively predictive description that works across the full range of experimental conditions.

In response, the authors introduce a theory‑neutral “waveguide kinetics” framework that reinterprets the steady‑state polarization curve (current versus overpotential) as a power‑flow response of the electrochemical interface. The key conceptual step is to map the applied overpotential η onto a dimensionless driving coordinate ξ = F η/(RT). The net current is then expressed as the difference between forward (oxidation‑directed) and backward (reduction‑directed) fluxes, each of which is decomposed into a small set of fundamental modes. In the simplest implementation two modes are sufficient:

• Mode 1 represents the primary catalytic pathway that generates the desired Faradaic current.
• Mode 2 captures a compensating or suppressing process (e.g., the sluggish alkaline HOR, surface poisoning, or any side reaction that reduces net current).

Each mode i is characterized by three physically interpretable parameters: a strength A_i, an asymmetry factor β_i, and a growth‑rate exponent γ_i. The current‑overpotential relationship takes the compact analytic form

 J(ξ) = ∑_i A_i