S7. Scanning electron micrographs of exfoliated graphene from Graphene production by cracking

In recent years, graphene has found its use in numerous industrial applications due to its unique properties. While its impermeable and conductive nature can replace currently used anticorrosive toxic pigments in coating systems, due to its large strength to weight ratio, graphene can be an important component as a next-generation additive for automotive, aerospace and construction applications. The current bottlenecks in using graphene and graphene oxide and other two-dimensional materials are the availability of cost-effective, high-quality materials and their effective incorporation (functionalization and dispersion) into the product matrices. On overcoming these factors, graphene may attract significant demands in terms of volume consumption. Graphene can be produced on industrial scales and through cost-effective top-down routes such as chemical, electrochemical and/or high-pressure mechanical exfoliation. Graphene, depending on end applications, can be chemically tuned and modified via functionalization so that easy incorporation into product matrices is possible. This paper discusses different production methods and their impact on the quality of graphene produced in terms of energy input. Graphene with an average thickness below five layers was produced by both methods with varied defects. However, a higher yield of graphene with a lower number of layers was produced via the high-pressure exfoliation route.This article is part of a discussion meeting issue ‘A cracking approach to inventing new tough materials: fracture stranger than friction’.近年来，石墨烯（graphene）凭借其独特的性能，已在众多工业领域得到应用。其不渗透性与导电性能可替代涂料体系中当前广泛使用的有毒防腐颜料；同时，凭借优异的比强度，石墨烯可作为下一代添加剂，应用于汽车、航空航天及建筑等领域。当前制约石墨烯、氧化石墨烯（graphene oxide）及其他二维材料（two-dimensional materials）应用的瓶颈，在于低成本、高品质材料的供给不足，以及如何将其有效掺入（功能化与分散）至产品基体中。若能突破上述瓶颈，石墨烯的体积消费量或将迎来显著增长。石墨烯可通过化学剥离（exfoliation）、电化学剥离及高压机械剥离等低成本自上而下的制备路径实现工业化规模生产。根据终端应用场景的需求，可通过功能化（functionalization）手段对石墨烯进行化学调控与改性，使其能够更便捷地掺入产品基体。本文探讨了不同的制备方法及其对所制备石墨烯品质的影响，重点围绕能量输入维度展开。两种方法均可制备出平均层数低于五层的石墨烯，但均存在不同程度的结构缺陷；不过，采用高压剥离工艺可获得更高产率的低层数石墨烯。本文属于‘A cracking approach to inventing new tough materials: fracture stranger than friction’专题讨论会议文集的一部分。