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

析氢反应（HER）是下一代聚合物电解质膜（PEM）水电解技术的阴极半反应，需要在酸性介质中使用耐腐蚀的催化剂来加速可再生能源的制氢。本论文系统研究了石墨烯负载的非贵金属HER催化剂在酸性电解液中的HER机理和耐腐蚀性能。电化学实验和计算机模拟表明，石墨烯的层数、化学掺杂和结构缺陷共同决定了质子的穿透程度及其HER机制。此外，设计覆盖石墨烯的厚度、掺杂水平和缺陷密度优化了催化活性和催化剂寿命（即抑制催化剂腐蚀）。因此，我首次揭示了HER活性主要由质子穿透石墨烯层的行为所控制。这一新发现将进一步改进传统概念，该传统概念仅关注从金属基底向覆盖最外石墨烯层的电荷转移效应，并且将显示对石墨烯覆盖技术的基本理解，该石墨烯覆盖技术用于改善非贵金属催化剂的可用性，不仅用于酸性HER过程，而且用于需要非贵金属防腐蚀的各种情况。

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.