Electrochemical characterization of laser-induced graphene electrodes and performance comparison to glassy carbon electrodes

Laser-induced graphene (LIG) has emerged as a versatile and high-performance carbon material in electroanalysis; however, the fundamental origins of its performance remain insufficiently clarified. Here, we systematically compare the electrochemical response of LIG electrodes with that of conventional glassy carbon electrodes (GCE) using complementary redox probes and model analytes. Double-layer capacitance measurements reveal that LIG provides an electrochemically accessible surface area nearly eight times larger than GCE, consistent with its porous morphology. Voltammetric and impedance analyses using outer-sphere and surface-sensitive probes demonstrate that increases in faradaic current at LIG arise primarily from an enlarged electrochemically active surface area and enhanced surface reactivity, rather than intrinsically faster electron-transfer kinetics. Experiments with methylene blue and adsorption-dependent analytes further confirm the high density of functional groups and the strong capacity of LIG to stabilize surface-bound species. Leveraging these characteristics, we apply an unmodified LIG electrode to the voltammetric determination of salicylic acid (SA) via a surface-mediated cathodic stripping strategy. The redox behavior of SA—known to generate adsorbed quinone-like intermediates—aligns particularly well with the defect-rich, oxygenated surface of LIG, enabling a low detection limit (0.18 µmol L⁻¹) and accurate quantification in water samples. These findings provide mechanistic insights into the electrochemical behavior of LIG and demonstrate how deliberate matching between electrode surface properties and analyte redox requirements can yield high-performance sensing platforms without the need for surface modification.