This study reports an efficient electroreduction of unactivated alkyl alkenes using water as a hydrogen source, enabled by [Fe]-H, generated through the combination of anodic iron salts and silane produced via cathodic reduction. The catalytic amount of Si-additive acts as an H-carrier from water to generate a highly active silane species in situ under continuous electrochemical conditions. This approach demonstrates broad substrate scope and good functional group compatibility. Additionally, using D₂O instead of H₂O provides deuterated products with excellent D-incorporation (up to >99%). The method also enables late-stage hydrogenation of complex molecules and drug derivatives, showing potential applications in the pharmaceutical industry. Mechanistic studies support the proposed mechanism, highlighting the crucial role of the H-carrier in the transformation.This study reports an efficient electroreduction of unactivated alkyl alkenes using water as a hydrogen source, enabled by [Fe]-H, generated through the combination of anodic iron salts and silane produced via cathodic reduction. The catalytic amount of Si-additive acts as an H-carrier from water to generate a highly active silane species in situ under continuous electrochemical conditions. This approach demonstrates broad substrate scope and good functional group compatibility. Additionally, using D₂O instead of H₂O provides deuterated products with excellent D-incorporation (up to >99%). The method also enables late-stage hydrogenation of complex molecules and drug derivatives, showing potential applications in the pharmaceutical industry. Mechanistic studies support the proposed mechanism, highlighting the crucial role of the H-carrier in the transformation.