Trialkylsilanes　are　important　building　blocks　in　organic　synthesis;　however,　their　widespread　use　in　redox　chemistry　is　limited　by　their　high　oxidation　potentials　and　comparably　high　bond　dissociation　energies　(BDEs)　of　Si-H　and　alpha-Si-C-H　bonds　(＞92　kcal　mol(-1)).　Herein,　we　report　a　new　strategy　for　Si-H　bond　homolysis　enabled　by　the　synergistic　combination　of　electrooxidation,　photoinduced　ligand-to-metal　charge　transfer　(LMCT),　and　radical-mediated　hydrogen　atom　transfer　(HAT).　Governed　by　the　polarity-matching　effect,　the　HAT　to　electrophilic　MeO.　or　[Cl-OHCH3]　from　the　more　hydridic　Si-H　instead　of　a　C-H　bond　allows　the　selective　generation　of　silyl　radicals.　This　electrophotocatalytic　protocol　provides　rapid　access　to　Si-functionalized　benzimidazo-fused　isoquinolinones　with　broad　functional-group　compatibility.　Mechanistic　studies　have　shown　that　n-Bu4NCl　is　essential　to　the　electrooxidation　of　CeCl3　to　form　the　Ce(IV)　species.　[GRAPHICS]　.