Secondly, the archetypal redox centers can be broadly grouped into eight categories explored so far (Table S1)3-4: nitroxide radical (bipolar), organodisulfide (n-type), conjugated thioether (p-type), etheroxide (p-type), amide (p-type), nitrile (n-type), azo (n-type), and carbonyl (n-type). The last one is the richest studied category, with already more than 100 derivatives reported thus far given their reactivity at anodic but also cathodic potentials, many-electrons charge storage capacities, as well as commercial availability and their natural occurrence (Figure S1).5-7 (pdf) (Wang 等。, 2021, p. 9)