## 1 Introduction  
Friction and wear phenomena are among the primary reasons for the reduced operational efficiency of both mechanical components and electrical components, and may lead to early components replacement. Lubricants are needed to reduce friction and wear at the interface of sliding parts. As for mechanical components, liquid or semi-solid lubricants (such as oils and grease) have always proved effective. However, traditional lubricants have to meet increasingly stringent performance and environmental compatibility constraints because they are extremely polluting substances when replaced and disposed of. Moreover, lubricants may be incompatible with electrical components due to their insulating properties. For these reasons, there has been a growing interest in solid lubricants and high lubricity coatings, including 2D nanomaterials [1], as an alternative to traditional lubricants. For instance, the papers by [PERSON] [2], [PERSON] et al. [3], [PERSON] et al. [4], [PERSON] et al. [5], and [PERSON] et al. [6] provide examples of present and prospective applications of solid lubricants in many fields of industry. In particular, issues related to wear associated to copper electrical contacts is a problem of actual importance that still needs a solution [7; 8; 9; 10]. Low friction coatings have many advantages compared to fluid lubricants when applied to reduce friction and wear. No lubrication system is needed in mechanical systems, whose design can be simplified, and no leakages or reubrication issues are present (operation and maintenance are more effortless). On the other hand, troubles may arise when coatings are applied to electrical components like connectors or switches. Many of them are insulating materials (e.g., ceramics or polymer composites), and their presence would impair the fundamental function of the systems, i.e., to conduct electricity. Efforts are being made to develop conductive low friction coatings and hard coatings to improve tribological properties and reduce wear in electrical devices without impairing their conductive properties. For instance, [PERSON] et al. [11] provided a broad overview of the electric conductivity properties of many solid coatings, highlighting that the most expedient route to enhance the conductivity of traditional coatings is the inclusion of carbon pigments or other metals pigments while boosting their corrosion resistance too. [PERSON] et al. [12] reported the effect of reinforcement of carbon nanotubes and graphene nanoplatelets on electrical conductivity of plasma-sprayed Al\({}_{2}\)O\({}_{3}\) coatings. Among the variety of materials used as friction reduction coatings, graphene layers have been investigated for the past few years by many authors in the scientific literature [13] for both mechanical and electrical applications since it was first isolated in 2004 [14]. Being a carbon compound, graphene is ideal for electrical application, thanks to its extremely high electrical conductivity, while serving as solid lubricant as well. Fascinating lubricant properties are attributed to graphene by [PERSON] et al. [15], who collected and revised in his paper many results from previous tribological investigations at the nanoscale and macroscale on a number of substrates. [PERSON] et al. [16] reported that the use of multi-layer graphene coating can effectively reduce the wearing-out of tiny electrical connectors and protect them from tribo-oxidation damage, without affecting the electrical conduction through the pair. [PERSON] et al. [17] explored the synergistic effect of TiN-Ag coating and MLG-rich grease to improve the friction, wear, and conduction of copper connectors. [PERSON] et al. [18] and [PERSON] et al. [19] studied copper matrix composites and aluminium matrix composites with added graphene, respectively. Their results showed that the presence of graphene enhanced the tribological behaviour while increasing the hybrid composition. The wear performances of other types of composite materials have been investigated in [20,21].