Heteroatom-Doped Carbon Materials for Multifunctional Noncatalytic Applications

The introduction of heteroatoms (i.e., atoms different from the carbon atom) with different sizes and electronegativities into a pure carbon structure offers a way to control the electron distribution within carbon materials. This heteroatom-doping process can improve their electrical, electrochemical, electronic, optical, thermal, and even mechanical properties, making them suitable for a diverse range of applications. While the use of heteroatom-doped carbon-based metal-free materials (C-MFMs) has been extensively reviewed for catalytic applications, a systematic review on their noncatalytic roles is still lacking. This review comprehensively analyzes the effects of heteroatom-doping (nitrogen, boron, sulfur, phosphorus, fluorine, etc.) on C-MFMs for multifunctional noncatalytic applications in energy storage (e.g., supercapacitors, secondary batteries, and hybrid capacitors). In addition to the energy-related uses, this review explores the recent developments of C-MFMs in photo/electronic devices (e.g., photovoltaic devices, photodetectors, field emission transistors, and light-emitting diodes), in the rapidly growing area of environmental remediation (for water and air purification) and medical applications (e.g., drug/gene delivery, bioimaging/sensing, and photothermal therapy). This review provides a detailed overview of the latest advancements in carbon-based materials used for these noncatalytic applications. Mechanistic insights into the influence of heteroatoms on material behavior will be discussed, alongside a focus on the present need for improved control over structure and more viable, scalable production. Finally, we will also discuss the impact of structure-property relationships in the use of C-MFMs and the opportunities for advancing these carbon-based materials through rational design strategies.