Investigating synergistic effects of biomass-derived carbon coatings on TiO2 for anode candidacy in electrochemical OER and supercapacitor performance enhancement

Abstract

Biomass-driven carbons are obtained from onion peels (C_onion), eggshells (C_egg), and banana peels (C_banana) and mixed in absolute ethanol in their weight ratio (C_a (1:1:1), C_b (1:1:2), C_c (1:2:1), C_d (2:1:1). These synergistic compositions are coated, individually, on TiO₂ as C_a@TiO₂, C_b@TiO₂, C_c@TiO₂, C_d@TiO₂, respectively. These samples are further explored for structural, morphological, and electrochemical performance. FTIR, XRD and SEM analysis confirm the formation, crystalline nature, and nanoscale range of the particles, respectively. Each uncoated (C) and coated (C@TiO₂) sample is then fabricated on Ni-foam to explore their electrochemical performance as anode materials in both OER and supercapacitor applications. OER analyses revealed that, among all the compositions (coated/uncoated), C_c@TiO₂ exhibit comparatively low values of onset potential (E_onset; 1.50 V), overpotential (η; 0.223 V), Tafel slope (65.6 mV/dec @ 10 mA/cm²), and solution resistance (R_s; 1.93 Ω) and find to be stable at current density of 56 mAcm⁻² during controlled potential electrolysis (CPE). The same TiO₂ coated composite shows comparatively better performance as anode material for supercapacitor with comparatively more promising electrochemical findings than that for other samples which include greater capacitance (C_sp; 617.43 F/g by CV@ 2 mVs⁻¹, 289.23 F/g by [email protected] A/g), longer discharging time (dt; 235 s), highest energy density with power density (E_d/P_d; 17.00 Whkg⁻¹/260.43 Wkg^-1 @ 0.8 Ag^-1), greater capacitance retention (⁓98 %) up to 1000 cycles, and lowest R_s. Hence C_c@TiO₂ could be considered as a potential anode candidate for energy storage devices.