Plasmonic catalysis is an emerging process that utilizes surface plasmon resonance (SPR) process to harnesses solar energy for the promotion of catalyzed reactions. In most cases, SPR generated hot electrons (HEs) play an indispensable role in this solar-chemical energy shift process. Therefore, understanding the effectiveness of the HEs in promoting chemical reactions, and identifying the key factors that contribute to this utilization efficiency is of profound importance. Herein, the authors outline an in situ surface enhanced Raman spectroscopy protocol to track the fate of HEs. This is based on the unheeded HEs-acceleration nature of the p-nitirothiophenol hydrogenation reaction. By this way, the authors discover that unlike Au@Pd nanostructures which experience a 20-fold increase in rate constant, HEs primary leak to surrounding H+ /O species through Ag pinholes in Ag@Pd. This work sheds light on why Ag is seldom employed as a plasmonic cocatalyst, and provides a new viewpoint to design plasmonic nanocatalysts with efficient light utilization.