ORIGINAL PAPER Galvanostatic synthesis of MnO 2 in carbon cloth: an electrochemical impedance spectroscopy study J. C. M. Costa 1 & M. C. Nascimento 1 & E. C. Silva 1 & B. L. Pereira 1 & R. R. Passos 1 & L. A. Pocrifka 1 Received: 10 December 2019 /Revised: 11 February 2020 /Accepted: 28 February 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract In the present work, MnO 2 was electrodeposited (galvanostatic mode) on carbon cloth (CC) from manganese nitrate and sulfate precursors. Its electrochemical performance was evaluated by cyclic voltammetry (CV) and electrochemical impedance spec- troscopy (EIS), which were used to study the complex behavior of the material. In CV analysis, higher cathodic and anodic loads were obtained for sulfate–MnO 2 compared with nitrate–MnO 2 , whereas in the Nyquist graphs of the EIS technique, the nitrate– MnO 2 material obtained larger charge transfer resistance (Rtc) than sulfate–MnO 2 . In the Bode analysis, the behavior of sulfate– MnO 2 was better than that of nitrate–MnO 2 . because for this analysis, the phase angle is smaller, which is attributed to better pseudocapacitive behavior of sulfate than nitrate. In capacitance and complex power terms, the relaxation time constant obtained was 2.65 s. The real capacitance in C′(ω) was 107 F g -1 for nitrate–MnO 2 and 197 F g -1 for sulfate–MnO 2 , and the intersection of the complex power curves occurred at 70%. The obtained results suggest that these materials are attractive for application in energy storage devices. Keywords Carbon cloth (CC) . Nitrate–MnO 2 . Sulfate–MnO 2 . Complex capacitance study Introduction Technological development and population growth have led to an exponential increase in global energy demand, and thus the need for increasingly efficient energy generation and/or storage systems [1]. In recent years, flexible and portable de- vices using carbon cloth (CC) have been developed for use as electronic sensors, uniforms, gowns and medical bandages [2, 3]. The fabrication of these fully flexible and wearable elec- tronic components has given rise to the need for adequate energy sources with small volume, light weight and good electrochemical performance, capable of transforming them into electrochemical capacitors [3, 4]. Moreover, the development of effective and low-cost elec- trochemical capacitors is a critical factor in the viability of industrial production. Materials employed in these capacitors include conducting polymers, carbon and transition metal ox- ides [5–7]. Among these, NiO, Co 3 O 4 , Ni(OH) 2 , MnO 2 have been investigated as electrode materials for electrochemical capacitors [8–11]; among these oxides, manganese in partic- ular is low-cost, nontoxic and abundant in nature [12, 13]. However, the pseudocapacitive behavior and conductivity of manganese oxide is still not fully understood [ 14]. Some research groups have studied this material [15–17] by electrochemical impedance spectroscopy (EIS). With EIS, it is possible to obtain information about charge transfer and diffusion processes and the loading of the double layer and the active layer of the material, which is not possible by cyclic voltammetry (CV) [18]. In the study of electrochemical capacitors, it is interesting to address data in terms of complex capacitance which also provides information on low-frequency capacitive responses, as electrochemical capacitors oscillate between high- frequency resistive and low-frequency capacitive states [19]. Shinde et al. [15] used EIS to study the influence of differ- ent temperatures in the hydrothermal synthesis of MnO 2 . Using the complex capacitance model, they observed better electrochemical performance in terms of complex capacitance for the synthesis conducted at 453 K. The calculated values were 92 mF cm -2 and 45 mF cm -2 in the real C′(ω) and imaginary C′′(ω) regions, respectively. These data correspond to the active and dissipated energies of MnO 2 . Recently Qi et al. [16] used pulsed electrodeposition to deposit MnO 2 and * L. A. Pocrifka pocrifka@ufam.edu.br 1 Department of Chemistry, Laboratory of Electrochemistry and Energy, Federal University of Amazonas, Manaus, AM, Brazil Journal of Solid State Electrochemistry https://doi.org/10.1007/s10008-020-04532-2