Structure-function correlations in graphene screen-printed electrodes: capacitive and faradaic behaviour

How the origin of graphene influences interfacial behaviour once it is formulate and screen-printed has been unclear. Herein, we fabricate four graphene screen-printed electrodes (commercial, combustion-derived, exfoliated, and CVD-grown) using an identical ink and printing protocol and combine conventional electroanalysis with step-potential electrochemical spectroscopy to obtain assumption-light differential capacitance <i>C</i>(<i>E</i>) and charging timescales <i>τ</i>. All electrodes show U-shaped <i>C</i>(<i>E</i>) with tightly clustered PZCs (0.35-0.40 V <i>vs.</i> Ag/AgCl), indicating that the charge-neutral potential is set primarily by surface chemistry and electronic structure, rather than morphology. However, the extent and speed of interfacial charging vary. The double-layer capacitance (<i>C</i>_dl) scales with wetting and mesoporosity, while the charging time (<i>τ</i> = 15-25 ms across the set) reflects the trade-off between ionic access resistance and capacitance. For the partially inner-sphere redox couple [Fe(CN)₆]^4-/3-, heterogeneous electron transfer follows edge, defect, and oxygen functionality, rather than film conductivity, with <i>k</i>⁰ spanning (0.76-1.99) × 10^-5 m s^-1. These interfacial electrochemical metrics, both capacitive and faradaic, map directly onto physical features such as porosity, defect density, and interfacial chemistry, providing initial criteria for selecting graphene precursors in sensing, catalysis, and energy storage.