Despite efforts to combine the plasmonic effect and the catalytic properties in metal-based catalysts, corresponding mechanistic studies based on electrochemical methods have to date remained challenging. In this context, the transition from plasmon metal to catalytic metal based core-shell heterostructures provides a sustainable route to catalytic activity and confirms the practical potential of plasmonmediated electrocatalytic performance. Here, we report the rational design of AuNPs wrapped with rGO spacer incorporating Pd catalyst (AuNP@rGO@Pd). Materials characterization together with the enhanced catalytic activity of both H2 and O2 generation using visible light inferred the advantageous incorporation of rGO with tuned layer thickness. Also, in situ observation of the plasmon-enhanced electrocatalytic properties during the reaction was utilized to advance understanding of the fundamental physical and chemical properties of high performance.