A state-of-the-art review on biomass-derived carbon materials for supercapacitor applications: From precursor selection to design optimization.

Biomass-derived carbon materials have the characteristics of a wide range of precursor sources, controllable carbon nano-dimension, large specific surface area and abundant heteroatoms doping. At present, biomass-derived carbon materials have been widely used in electrochemical energy storage devices, especially the research and development of biomass-derived carbon materials for supercapacitors has become mature and in-depth. Therefore, it is of importance to summarize the advanced technologies and strategies for optimizing biomass-derived carbon materials for supercapacitors, which will effectively promote the further development of high-performance supercapacitors. In this review, the recent research progress of biomass-derived carbon materials is provided in detail, including the selection of biomass precursors, the design of carbon nano-dimension and the theory of heteroatom doping. Besides, the preparation methods of biomass-derived carbon materials and the related processes of optimizing the electrochemical performance are also summarized. This review ends with the perspectives for future research directions and challenges in the field of biomass-derived carbon materials for electrochemical applications. This review aims to provide helpful reference information for the nano-dimensional design and electrochemical performance optimization of biomass-derived carbon materials for the practical application of supercapacitors.

Syngas Production from Biomass Gasification: Influences of Feedstock Properties, Reactor Type, and Reaction Parameters.

Syngas from biomass gasification can be used in downstream process industries such as city gas, hydrogen production, etc. In this review, the effects of biomass feedstock properties, and gasification reaction conditions (temperature, gasifier type, etc.) on syngas properties are systematically reviewed. In summary, the cracking and reforming of volatile fractions in the gasification process and the catalytic effect of alkali and alkaline earth metals in the ash on the gasification have a direct impact on the syngas yield. And biomass pretreatment (i.e., terrifying/hydrothermal carbonization) can reduce the moisture content, which can effectively reduce the energy required for gasification and enhance the calorific value and syngas yield further. The fixed-bed gasifiers produce lower amounts of syngas. The concentration of H2 is significantly increased by adding steam as a gasification agent. Additionally higher gasification temperatures produce more syngas, and an equivalence ratio of about 0.2-0.3 is considered suitable for gasification. For the influence of feedstock on syngas, this paper not only reviews the feedstock properties (volatile, ash, moisture) but also compares the influence of two pretreatments on syngas yield and proposes that the combination of torrefaction/hydrothermal carbonization and a multistage air bed gasifier is an important research direction to improve the combustible components of syngas. In addition to the summary of commonly used single gasification agents, two or more gasification agents on the concentration of syngas components are also discussed in the gasification parameters, and it is suggested that further research into the use of more than one gasification agent is also important for future syngas production.