A　photoelectrochemical　(PEC)　sensing　system　for　H2O2　detection　had　been　proposed　based　on　parallel　catalytic　method　in　the　presence　of　a　ferrocene　derivative.　3,3-bis(1-ferrocene　methyleneimidazole-3-)　boron　dihydrodicyanamide　([Fcmim][N(CN)2])　was　synthesized　and　immobilized　on　the　surface　of　a　GaN　photoanode　by　the　Nafion®　film.　A　circulating　H2O2-O2-H2O2　system　was　constructed　using　[Fcmim][N(CN)2]　as　bifunctional　catalyst.　In　the　cyclic　process,　H2O2　is　catalyzed　by　[Fcmim][N(CN)2]　to　produce　O2,　which　is　then　reduced　to　H2O2　by　photogenerated　electrons　of　GaN.　The　reduction　process　of　O2　is　also　catalyzed　by　the　same　ferrocene　catalyst.　The　regenerated　H2O2　continues　to　be　decomposed,　causing　O2　and　H2O2　to　fall　into　a　photoelectrochemical　cycle　of　H2O2-O2-H2O2.　The　decrease　of　the　photocurrent　by　O2　was　markedly　amplified　because　the　H2O2　and　O2　were　periodically　regenerated.　On　the　other　hand,　the　diffusion　rate　of　dissolved　O2　through　the　Nafion®　film　is　lower　than　the　photoelectrochemical　reduction　rate　of　O2　on　the　GaN　photoanode,　thus　the　interference　of　dissolved　O2　in　the　solvent　could　be　eliminated　during　repeated　on/off　cycles　of　illumination.　In　the　range　of　4.00　nM　-　0.720　μM　and　the　limit　of　detection　was　1.23　nM　(3　S/N),　PEC　signal　is　linearly　correlated　with　the　logarithm　of　H2O2　concentration　under　optimized　conditions.　This　method　has　a　wide　application　prospect　in　environmental　analysis　and　food　safety　analysis.　For　example,　bilirubin　can　be　detected　using　Nafion®　in　combination　with　bilirubin　oxidase　and　[Fcmim][N(CN)2].　©　2022　Elsevier　B.V.