Fundamental investigations of corrosion-proof and active non-noble-metal catalysts via graphene encapsulation for efficient hydrogen productions

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Hydrogen evolution reaction (HER), the cathodic half reaction of the next-generation polymer electrolyte membrane (PEM) water electrolysis technology, requires corrosion-proof catalysts in acidic media to accelerate the hydrogen productions by using renewable energy sources. In this study, I systematically investigated the HER mechanism and corrosion-proof ability of graphene-covered non-noble metal HER catalysts in acidic electrolytes. The electrochemical experiments and computational simulations demonstrated that the layer number, chemical doping, and structural defects on the graphene cooperatively determined the degree of proton penetration, and their HER mechanisms. In addition, engineering the thickness, doping level, and defect density of covering graphene optimized the catalytic activity and catalyst life time (i.e. suppression of catalyst corrosion). Consequently, I firstly revealed that the HER activity was majorly governed by the proton penetration behavior through graphene layers. This new finding will further improve the traditional concept which only focused on the charge transfer effect from the metal substrate towards the covering outmost graphene layers and will show a fundamental understanding on the graphene covering technology for improving the usability of non-noble metal catalysts not only for the acidic HER process, but also for various circumstances that require the corrosion-proofing of non-noble metals.