The　homogeneous　electrocatalytic　mechanism　with　a　fast　catalytic　chemical　reaction　between　a　series　of　ferrocene　derivatives　and　L-cysteine/N-Acetyl-L-cysteine　(NAC)　is　systematically　investigated.　A　comparison　of　different　cyclic　voltammetric　waveforms　is　given　to　illustrate　the　interaction　between　kinetic　parameter　(l)　and　excess　factor　(g)　in　kinetic　zone　diagram　via　changing　the　scan　rates　and　substrate/mediator　ratio　on　both　glassy　carbon　(GC)　and　boron　doped　diamond　(BDD)　working　electrode　experimentally.　A　split　wave　phenomenon　is　observed　between　ferroceneacetic　acid　(FAA)　and　L-cysteine.　Also,　the　waveforms　revealed　that　electron　withdrawing　groups　(EWG)　on　the　substrate　hinders　the　kinetics　of　the　homogeneous　electron　transfer　while　those　on　the　mediator　facilitates　the　same　process.　The　homogeneous　electrocatalytic　order　of　the　studied　mediator　is　as　follows:　1,10-ferrocenedicarboxylic　acid　(FDA)　＞　FAA　＞　hydroxymethylferrocene　(HMF)　＞　1-hydroxyethylferrocene　(HEF)　and　the　corresponding　density　functional　theory　(DFT)　calculation　is　applied　to　support　this　statement.　Furthermore,　the　second-order　rate　constant　between　FAA　and　L-cysteine　is　given　by　the　support　of　numerical　simulation　(175　(mol　m(-3))(-1)　s(-1)).　The　present　study　would　facilitate　the　understanding　of　homogeneous　electrocatalytic　process,　especially　those　possessing　a　fast　catalytic　chemical　step.　(C)　2020　Elsevier　Ltd.　All　rights　reserved.