Solution-Processed Graphene Thin-Film Enables Binder-Free, Efficient Loading of Nanocatalysts for Electrochemical Water Splitting

Electrochemical water splitting is promising to produce high purity hydrogen that can serve as clean and renewable energy. Reducing the size of catalysts down to the nanometer regime is critical for enhancing the electrochemical performance because reactions mostly occur at the surface of materials. However, fully exploiting the advantage of small nanocatalysts is challenging because accessible catalytic surface area is reduced by particle aggregation and the use of binders. In addition, a significant fraction of nanocatalysts is lost through the electrode pores during catalyst loading. Here, a simple strategy to efficiently load nanocatalysts without using binders is reported. By introducing a thin layer of graphene nanosheets on a porous membrane, a uniform nanocatalyst film via vacuum filtration of the dispersion can be created. The nanocatalyst/graphene composite can be transferred to a carbon paper without fracturing to function as a catalyst layer. The method is compatible with various nanomaterials to realize electrodes for hydrogen and oxygen evolution reactions and even bifunctional electrodes that exhibit activities for both. Significantly, the resulting electrodes show better performance than those produced by directly filtrating through the carbon paper. Moreover, the binder-free surface allows for further enhancement in catalytic activity via postchemical treatments.