Effects of oxygen-containing functional groups on carbon materials in supercapacitors: A review

Carbon materials play an indispensable role in supercapacitor devices. However, carbon materials based on the electric double-layer energy storage mechanisms limit the energy density improvement of supercapacitors. The introduction of additional redox pseudocapacitance through oxygen-containing functional groups is a novel strategy to improve the specific capacity of carbon materials. Whereas the influence mechanism of oxygen-containing functional groups on carbon-based electrode materials needs to be explored in-depth. Here, we summarize the types, introductions and characterization methods of oxygen-containing functional groups in carbon materials, and emphatically explain the effect of oxygen-containing functional groups on the structure and physico-chemical properties of carbon-based electrode materials for supercapacitors at the mechanism level, which has not been reported in previous reviews. Different types or content differences of oxygen-containing functional groups can cause changes in the polarity, surface energy, adsorption energy, impedance, energy bands and other aspects of carbon materials, and even lead to defects affecting the structure and physicochemical properties. The mutual constraint relationship between high specific capacity and excellent conductivity caused by the content of oxygen-containing functional groups is also pointed out. Carbon materials with rich oxygen are expected to be developed in lithium/sodium-ion batteries, fuel cells, electrocatalysis, sensor devices, biomedicine and other fields.