A review of graphene assembled films as platforms for electrochemical reactions

Abstract

Because of their low electrical conductivity, sluggish ion diffusion, and poor stability, conventional electrode materials are not able to meet the growing demands of energy storage and portable devices. Graphene assembled films (GAFs) formed from graphene nanosheets have an ultrahigh conductivity, a unique 2D network structure, and exceptional mechanical strength, which give them the potential to solve these problems. However, a systematic understanding of GAFs as an advanced electrode material is lacking. This review focuses on the use of GAFs in electrochemistry, providing a comprehensive analysis of their synthesis methods, surface/structural characteristics, and physical properties, and thus understand their structure-property relationships. Their advantages in batteries, supercapacitors, and electrochemical sensors are systematically evaluated, with an emphasis on their excellent electrical conductivity, ion transport kinetics, and interfacial stability. The existing problems in these devices, such as chemical inertness and mechanical brittleness, are discussed and potential solutions are proposed, including defect engineering and hybrid structures. This review should deepen our mechanistic understanding of the use of GAFs in electrochemical systems and provide actionable strategies for developing stable, high-performance electrode materials.

1. Introduction

Amidst rapid advancements in transportation, information technology, and healthcare sectors, the surging demand for energy storage and portable devices has imposed unprecedented challenges on electrochemical technologies. At present, batteries and capacitors dominate in energy storage systems, but their limited energy density and cycle life still could not meet the existing needs. Therefore, new materials need to be developed to improve their performance. Concurrently, the slow detection speed and poor reproducibility of current electrochemical sensors critically restrict their applications in sensing. Traditional metals and their alloys have been widely employed in electrochemical energy storage and sensing[1–9]. However, their complex fabrication processes, susceptibility to corrosion, high mass density, poor flexibility, and reliance on non-renewable resources pose critical constraints on technological innovation[10–18].

Carbon-based electrode materials, as a core material system in electrochemical energy storage, have emerged as a frontier research hotspot due to their unique physicochemical properties[19–24]. Compared to traditional metal or metal oxide electrodes, carbon materials exhibit multidimensional advantages: (1) Their abundant raw material sources and mature synthesis processes significantly reduce economic barriers for large-scale applications. (2) Their exceptional chemical inertness within a wide voltage window effectively suppresses side reactions such as electrolyte decomposition. (3) Their biocompatibility expands application potential in specialized scenarios like implantable medical devices. Structurally, carbon materials form diverse configurations, including graphene, carbon nanotubes, and porous carbons, through flexible combinations of sp2/sp3 hybridized bonds. This structural tunability enables precise regulation of surface electronic states, pore topology, and defect concentrations, exemplified by nitrogen-sulfur co-doping achieving active site densities up to 1020 cm−3. By integrating superior electron transport properties with optimized ion diffusion pathways, carbon-based materials fulfill multifunctional roles in energy storage systems: as active material carriers, their high specific surface area enhances charge storage density; as conductive additives, they form a 3D interconnected network, which not only enhances electron transport in silicon-based anodes but also mechanically confines volume expansion, thereby leading to significant improvements in electrochemical performance.