Tuning capacitance of bimetallic ZnCo₂O₄ using anionic, cationic and non-ionic surfactants by hydrothermal synthesis for high-performance asymmetric supercapacitor

Surface properties of nanomaterials are directly related to their electrochemical performance, with surfactants playing an essential role in their cost-effective synthesis as structure-directing agents and templates. This research article discusses the effects of neutral, cationic, and anionic surfactants on the capacitance of bimetallic ZnCo₂O₄ nanomaterial, synthesized via a straightforward hydrothermal-annealing method. We investigated how cationic (cetyl-trimethyl ammonium bromide), anionic (sodium dodecyl sulphate), and non-ionic (urea) surfactants influence the electrochemical characteristics of ZnCo₂O₄ nano-powders. All three surfactant-based ZnCo₂O₄ electrodes exhibited Faradaic behaviour during electrochemical tests. The ionic nature of the surfactants significantly impacted the charge-storage mechanism, with specific capacitance values rising in the order of Urea (550 Fg⁻¹) < C-TAB (740 Fg⁻¹) < SDS (980 Fg⁻¹) at a 1 Ag⁻¹ in half-cell studies. The ZnCo₂O₄-SDS displayed the highest surface redox reactivity and superior electrochemical performance, with 426 Fg⁻¹ in full-cell studies, energy density of 230 WhKg⁻¹ (1 Ag⁻¹), power density of 18,213.9 WKg⁻¹ (10 Ag⁻¹), and 93 % capacitance retention is observed over 50,000 cycles (50 Ag⁻¹).