Rational Surface Tailoring Oxygen Functional Groups on Carbon Spheres for Capacitive Mechanistic Study

Abstract

Porous carbons represent a typical class of electrode materials for electric double-layer capacitors. However, less attention has been focused on the study of the capacitive mechanism of electrochemically active surface oxygen groups rooted in porous carbons. Herein, the degree and variety of oxygen surface groups of HNO3-modified samples (N-CS) are finely tailored by a mild hydrothermal oxidation (0.0–3.0 mol L–1), while the micro–meso–macroporous structures are efficiently preserved from the original sample. Thus, N-CS is a suitable carrier for separately discussing the contribution of oxygen functional groups to the electrochemical property. The optimized N-CS shows a high capacitance of 279.4 F g–1 at 1 A g–1, exceeding 52.8% of pristine carbon sphere (CS) (182.8 F g–1 at 1 A g–1) in KOH electrolyte. On further deconvoluting the redox peaks of cyclic voltammetry curves, we find that the pseudocapacitance not only associates with the surface-controlled faradic reaction at high scan rate but also dramatically stems from the diffusion-controlled capacitance through potassium and hydroxyl ion insertion/deinsertion into the underutilized micropores at low scan rate. The assembled supercapacitor based on N-CS presents a stable energy density of 5 Wh kg–1 over a wide range of power density of 250–5000 W kg–1, which is higher than 0.0N-CS in KOH electrolyte. In TEABF4 electrolyte, the N-CS supercapacitor has an energy density of 26.9 Wh kg–1 at the power density of 1350 W kg–1 and exhibits excellent cycling stability with a capacitance retention of 93.2% at 2 A g–1 after 10 000 cycles. These results demonstrate that surface oxygen groups alter the capacitive mechanism and contribution of porous carbons.

Surface Oxygen Functionalization of Carbon Cloth toward Enhanced Electrochemical Dopamine Sensing

“…It can be observed that the signal intensity of the O element increased after treatment, while the signal intensity of the C element was almost unchanged, which can also be verified in the C 1s and O 1s core-level spectra (Figure c,d). From the C 1s spectrum, the peaks at 284.8, 286.0, 287.1, 289.1, and 291.7 eV were obtained after peak deconvolution, revealing the existence of C–C/CC, hydroxyl (C–O), carbonyl (CO), carboxyl (O–CO), and π–π shake-up satellite peak. − The percentages of individual carbon-containing functional groups are calculated according to their peak areas (Table S2). To figure out the species of groups that dominate in the increase of O content, the O 1s spectrum was also analyzed.…”

Uniform Zn Deposition Achieved by Conductive Carbon Additive for Zn Anode in Zinc‐Ion Hybrid Supercapacitors

“…The C−O stretching vibration corresponds to the peak at 1058 cm −1 , which may indicate the presence of ester, epoxide, ether, and phenol groups. [ 47–49 ] Furthermore, X‐ray photoelectron spectroscopy (XPS) is conducted to further confirm the types of chemical bonds (Figure 1f). Specifically, three fitting peaks can be observed in the high‐resolution O 1 s spectrum, attributed to the CO, OCO, and chemisorbed O, respectively.…”

Effect of pore structure and doping species on charge storage mechanisms in porous carbon-based supercapacitors

“…Therefore, an unreasonable increase in the proportion of oxygen functional groups will tightly trap ions and reduce the probability of ion intercalation. 99 Compared with aqueous electrolytes, organic electrolytes provide a broader electrochemical stability window (42 V), which can significantly boost the energy densities of electric double-layer capacitors. 100 At present, the majority of commercial electric double-layer capacitors utilize organic electrolytes.…”