Summary Direct liquid fuel cell (DLFC) is one of the leading fuel cell types due to their great features of superior energy density, modest configuration, small size in fuel container, immediate boosting, and effortless storage and carriage. Commercially used liquid fuel types are prepared using alcohols, such as methanol or ethanol, glycol, and acids. DLFCs face great challenges although they are potentially far‐reaching depending on the expensive catalysts and the use of high‐loading catalyst. More questions that should be addressed to ensure excellent DLFC performance include cathode flooding, fuel crossover, numerous side yield production, fuel security, and unverified elongated‐duration robustness. Further studies need to be carried out to ensure the continuous improvement of the quality of DLFCs' performance and their penetration in the commercial market. To date, direct liquid fuel cells made of methanol and ethanol have been successfully produced in commercial scale, but other types of DLFCs are still under study. In this review, introduction to DLFC will be discussed by covering work and commercialization as well as recent progress and challenges encountered.

Summary Carbon quantum dots (CQD) and graphene quantum dots (GQDs) have been mentioned frequently. They have been selected in recent studies as they have unique and remarkable potential, especially in electrical, optical, and optoelectrical properties. CQD and GQDs have very high chemical and physical stability due to inherent inert carbon material, thus newly recognized as a kind of quantum dots material. Its environmentally friendly, non‐toxic, and naturally inactive nature is also a major attraction for scientists around the world. In this work, CQD and GQDs production methods are discussed in detail, including soft‐template method, hydrothermal method, microwave‐assisted hydrothermal (MAH) method, metal‐catalyzed method, liquid exfoliation method, electron beam lithography method, and others. Additive material has been introduced in CQD and GQDs to increase the ability and performance of CQD and GQDs such as nitrogen, sulfur, chlorine, fluorine, and potassium. In particular, the presence of additive material in CQD and GQDs shows an advantage in terms of energy level, which is very good at achieving specific requirements in properties such as optical, electrical, and optoelectrical. In addition, the existence of functional groups consisting of heteroatoms such as oxygen, nitrogen, sulfur, phosphorus, boron, and so on of zero‐dimensional carbon materials in providing an overabundance of the active electrochemical site for the reaction. The product of CQD and GQDs has various shapes and sizes influenced by several parameters such as synthesis temperature, growth time, source concentration, catalyst, and so on. The application of CQDs and GQDs composites in fuel cells has been clearly and scientifically stated as it has enhanced the performance of fuel cell technology.

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Summary Thermal interface materials (TIMs) are applied in electronic devices that are involved in heat generation and raising the temperature. The optimization of TIMs is important in heat dissipation to maintain the good performance of devices, low power during operation, and reduced internal damages among small components. The TIMs are inserted between two contact surfaces to enhance thermal conductivity that will reduce the increment of surface temperature in a longer time and facilitates the cooling process with a consistent power supplied to the system with minimum increment. Research on nanomaterials and hybrid materials aims to obtain maximum thermal conductivity and reduce resistance in the devices. However, the suitable fabrication method for achieving good production and performance is still debatable. Therefore, significant fabrication methods have been explored for various materials. This review provides insights into the current work focusing on the materials used in the development of TIMs by various methods. The discussion begins with the introduction of thermal management and the working principles applied in the system. Then, the methods applied for material fabrication into TIMs, including the advantages and disadvantages of the methods, are discussed. Last, the current challenges and opportunities in methods used are discussed to offer new inputs and improvement in method modification for TIMs design. The targeted thermal performance for the industrial market of TIMs for nanomaterial applications is approximately 100 W/mK and 1 × 10−6 m2/WK with lowest power of 100 W.

Summary The performance of allotrope carbon materials has been explored because of their superior properties in energy system applications. This review provides an understanding of the current work focusing on the applications of selected carbon materials in important energy systems, focus on thermal interface materials (TIMs), and fuel cell applications. This article begins with the introduction of TIMs and fuel cell in general working principle and presents details on carbon materials. The discussion focuses on updates from the latest research work and addresses current challenges and opportunities for research toward TIMs and fuel cell applications. The optimum performance of TIMs was seen when thermal conductivity achieved at a maximum of 3000 W (m K)−1 by using vertically aligned carbon nanotubes (CNTs) and a minimum internal thermal resistance of 0.3 mm2 K W−1. Meanwhile for fuel cell, the platinum/CNTs catalyst applied proton exchange membrane fuel cell achieved high power density of 661 mW cm−2 in the presence of Nafion electrolyte membrane. This review provides insights for scientists about the use of carbon materials, especially in energy system applications.