Specific capacitance behavior of Co‐Co ₃ O ₄ nanocomposite thin films synthesized via different electrodeposition modes

Abstract

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.

Direct growth of three-dimensional nanoflower-like structures from flat metal surfaces

“…2F shows the O1s deconvolution peaks at ∼530.8, ∼531.1, ∼532.1, and ∼533.2 eV, corresponding to the lattice oxygen, defect oxygen, adsorbed oxygen (O ads ) and adsorbed H 2 O species. 1 b ,9 The percentages of the defect oxygen (including O ads ) and the lattice oxygen were calculated to be 35% and 54% for the sample annealed at 250 °C indicating its semi-amorphous nature (Fig. 2Fa), which agrees with the Raman results.…”

“…2Fa), which agrees with the Raman results. 8,9 In the case of 550 °C, the defect oxygen (including O ads ) was increased to 50%, while the lattice oxygen was decreased to 39%, revealing that the Co 3 O 4 crystallites with spinal structures were introduced with oxygen vacancies at 550 °C. 9 c The increase of oxygen vacancies would increase the projected density of states and conductivity, thus enhancing the electrochemical activity.…”

“…The dramatic increase of OER catalytic ability at 550 °C can be attributed to the high EASA due to the formation of well-defined Co 3 O 4 nanoflowers with oxygen vacancies induced into the crystal lattice. 9 c ,10 On the other hand, the thermal treatment at 650 °C caused aggravated phase transformation of Co 3 O 4 to CoO, 8,9 which resulted in poor electrocatalytic activity again (Fig. S7A, ESI†).…”

“…The multi-peak envelop fitting of five peaks of Co2p 3/2 due to multiplet splitting (∼780, ∼780.5, ∼781.9, ∼786.2, ∼790 eV) confirmed that the formed Co 3 O 4 comprises both the Co 2+ and Co 3+ states at a ratio of 1 : 2. 1,9 Fig. 2F shows the O1s deconvolution peaks at ∼530.8, ∼531.1, ∼532.1, and ∼533.2 eV, corresponding to the lattice oxygen, defect oxygen, adsorbed oxygen (O ads ) and adsorbed H 2 O species.…”