Physical-Chemical Interfacial Processes Across Graphene-Family Nanomaterials: Interplay of Electronic Structure with Defects and Quantum Capacitance

In this talk, we will present a combined experimental-theory investigation of the mechanistic outer-sphere electron transfer (OS-ET) kinetics in an adiabatic regime for a cornerstone electrochemical reaction, fundamental to efficient energy interconversion as in electrochemical double layer supercapacitors, across graphene-family nanomaterials (GFNs) ranging from pristine graphene to nitrogen-doped graphene aerogel and the novel laser-induced graphene. Using scanning electrochemical microscopy (SECM) operating in feedback mode and co-located spectroscopy, the ET rate constant, k⁰ (or k_ET, cm/s), was quantified while imaging electroactivity of OS potassium hexacyanoferrate (III/IV) [Fe (CN)₆^4-/3-] or ferrocene methanol [Fc⁰/Fc⁺] redox marker, yielding unexpected trends. We examined factors affecting the kinetic rate constant, rationalized through a physical model, and parameterized using density functional theory with the incorporation of defects and dopants. We attributed the improved kinetic rates (0.01-0.1 via SECM) compared with ensemble-averaged method (0.001-0.01 cm/s) to point-like topological defects in basal plane (number density ~10¹²/cm²), oxygen functional groups (C/O ratio: 4:1-12:1) and nitrogen doping, edge plane hydrogen-bonding sites (density: 0.1-1.0 μm^-1), altered electronic structure factored into available density of states near Fermi level (-0.2-+0.2 eV), and quantum capacitance. We elucidated the ET kinetics tunability by engineering the electronic band structure, varying electrode potential, and morphological diversity. Gupta et. al., Sci. Rep. (2025).