Unraveling the importance of controlled architecture in bimetallic multilayer electrode toward efficient electrocatalyst

Even though traditional electrode fabrication methods such as simple mixing process have been used in various energy storage and conversion devices due to its handiness, these methods could not fully utilize and maximize the intrinsic properties of each active material. With the limited control over the internal structure of the electrode, it also often poses a significant challenge to elucidate the structure-property relationship between components within the electrode. Taking advantages of versatile layer-by-layer (LbL) assembly which can tailor nano-architecture of hybrid electrodes, here we report electrocatalytic thin films for methanol oxidation by adjusting the assembly sequence of LbL films composed of the Au and Pd nanoparticles (NPs) and graphene oxide (GO) nanosheets. In case of co-assembled bimetallic LbL structure of (GO/Au/GO/Pd)_n where respective Au and Pd NPs are supported with GO nanosheets, the electrocatalytic activity is significantly higher than that of respective monometallic LbL electrode (i.e. (GO/Au)_n and (GO/Pd)_n). To further investigate the architecture effect on the electrochemical behavior, Au and Pd NPs are assembled with GO in a different relative position of hybrid multilayer electrodes. It is proved that the electrocatalytic activity can be highly tunable by the position of metal NPs in the LbL structure, suggesting the structural dependence of charge and mass transfer between the electrolyte and the electrode, which is otherwise impossible to investigate in a simple conventional electrode fabrication method. Because of the highly tunable properties of LbL assembled electrodes coupled with electrocatalytic NPs, we anticipate that the general concept presented here will offer new insights in the nanoscale control over the architecture of the electrode toward development of novel electroactive catalysts.