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A combined cyclic voltammetry and pulse reverse potential electrodeposition technique has been used to synthesize carbon-free Ni/NiO nanocomposite thin film supercapacitor electrode. The structural and morphological analyses have revealed the presence of crystalline phases of both Ni and NiO in the form of nanospheres of size ~ 50 nm. The electrochemical analysis of the Ni/NiOna nocomposite electrode has shown a remarkable performance by delivering a high specific capacitance of 2000 Fg−1 at an applied current load of 1 Ag−1 and a capacitance retention of 98.6%, after over 800 cycles under a high current load of 20 Ag−1.

High capacitance Co-Co 3 O 4 nanocomposite thin films have been synthesized on nickel foam (NF) using cyclic voltammetry (CV), combination of cyclic voltammetry and potentiostatic (CV PS À1.4 V and CV PS +1 V), and combination of cyclic voltammetry and pulse reverse potential (CV PRP) modes of electrodeposition. X-ray diffraction (XRD) studies reveal the presence of Co and Co 3 O 4 phases for the four electrodeposition modes. The scanning electron microscope (SEM) revealed an interesting morphology correlating the electrochemical and capacitance behavior, while the energy-dispersive X-ray spectroscopy (EDX) spectra confirmed the varying quantities of Co and O in the Co-Co 3 O 4 nanocomposite thin films. The presence of Co-O bonds were also confirmed by the attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra obtained on these films. The capacitance values of Co-Co 3 O 4composite thin films obtained by CV, CV PS À1.4 V, CV PS +1 V, and CV PRP, respectively, were found to be 1661, 1400, 1866, and 2580 F g À1 at an applied current load of 1 A g À1 , while the capacitance retentions after 500 cycles under a high current load of 20 A g À1 for the same were 85.8%, 77.8%, 87.1%, and 90.5%, respectively. The high capacitance and their retention of the electrodeposited Co-Co 3 O 4 nanocomposite thin films show potentials as high-performance supercapacitor electrode.

Summary Nanostructured Ag‐decorated Co‐Co3O4 composite thin film (Ag/Co‐Co3O4) synthesized on nickel foam (NF) by a combination of cyclic voltammetry and pulse reverse potential electrodeposition modes presents higher specific capacitance and its retention. The higher specific capacitance of 2800 F/g on Ag/Co‐Co3O4/NF composite thin film in comparison with 2580 F/g on Co‐Co3O4/NF at 1 A/g is attributable to the presence of nanostructured Ag in the composite film enhancing the ionic and electronic conductivity of the material. The morphology revealed by the scanning electron microscope correlates the electrochemical and capacitance behavior while the energy‐dispersive X‐ray spectroscopy spectra confirmed the presence of Co, Ag, and O in the Ag/Co‐Co3O4/NF composite thin film. The attenuated total reflection‐Fourier transform infrared spectra obtained further confirmed the presence of Co–O bonds. The Ag/Co‐Co3O4/NF composite thin film presented an amorphous nature as revealed by the X‐ray diffraction spectra. In addition, the Ag/Co‐Co3O4/NF electrode exhibited a maximum specific energy of 69.5 Wh/kg, specific power of 6.6 kW/kg and capacitance retention of 82.6% after 1000 cycles, while the Co‐Co3O4 electrode (with no Ag) showed lower specific energy of 60.8 Wh/kg, specific power of 5.8 kW/kg, and a capacitance retention of 78.2% after 1000 cycles. Furthermore, by the incorporation of Ag, the composite electrode showed a reduction in the equivalence series resistance value from 1.5 Ω cm2 (Co‐Co3O4/NF) to 1.0 Ω cm2 (Ag/Co‐Co3O4/NF) as well as in the charge transfer resistance (Rct) from 2.86 Ω cm2 (Co‐Co3O4/NF) to 0.96 Ω cm2 (Ag/Co‐Co3O4/NF) indicating the positive influence of the presence of Ag in the film. The electrochemical evaluation indicates that a synergistic effect between Ag and Co‐Co3O4 enhances supercapacitor electrode performance.

Nanostructured Co−Co 3 O 4 composite thin films deposited on nickel foam (NF) using combined cyclic voltammetry (CV) and pulse reverse potential (CV PRP) modes of electrodeposition from an electrolyte composed of CoCl 2 and Co(CH 3 COO) 2 precursor salt solutions with varied molar ratios demonstrated a dependency of the supercapacitance performance over the precursor components' molar ratios. The specific capacity and its retention were found to increase with increasing CoCl 2 in the electrolyte with a starting value of 474.6 C/g (791 F/g) at an applied current load of 1 A/g for a molar ratio of Co(CH 3 COO) 2 :CoCl 2 of 100:0. High specific capacity of 1548 C/g (2580 F/g) and large retention (90.5%) were obtained at a critical molar ratio of Co(CH 3 COO) 2 :CoCl 2 of 20:80. However, with 100% CoCl 2 in the electrolyte, the specific capacity lowered to 276 C/g (460 F/g) with poor retention of only 60%. Crystallinity and morphological features, driven by the electrolyte concentration with molar variations of the deposited films, have been found to influence the specific capacitance performance. The degree of crystallinity, and the presence of Co and Co 3 O 4 phases for the different molar ratios have been revealed by X-ray diffraction (XRD) studies. The diverse morphological features obtained by scanning electron microscopy (SEM) and the varying quantities of Co and O in the Co−Co 3 O 4 nanocomposite thin films as confirmed by energy-dispersive X-ray spectroscopy (EDX) spectra correlate well with the electrochemical performance. The phase composition was further confirmed by the presence of Co−O bonds via the attenuated total reflection−Fourier transform infrared (ATR-FTIR) spectra obtained on these films.