In the past decades, fossil energy depletion, environmental pollution, and greenhouse gas emissions have resulted in serious health threats and ecological imbalances, which prompt researchers to explore green and sustainable supercapacitor energy storage and conversion systems. Biomass is a promising renewable energy source to use for biomass porous carbon for supercapacitor devices because it is renewable and has abundant reserves, a low price, and low pollution carbon energy. To date, although some reports have screened different biomass precursors, carbonization methods, and activation strategies and mechanisms, a comprehensive evaluation and critical review of the correlation among biomass porous carbon properties, including pore structure and surface chemistry, and electrochemical energy storage performances of supercapacitors are absent from a multidisciplinary assessment perspective. Therefore, in this review, we summarize recent advances in the biomass porous carbon synthesis process focusing on different carbonization and activation strategies, point out the scope of applicability and advantages/disadvantages of these methods in supercapacitor applications, and reveal the reaction mechanisms and limitations for commercial production. Then, the relationships among biomass porous carbon properties, including hierarchical porous structure, surface chemistry, specific surface area, and electrochemical performances of supercapacitors are reviewed in detail, which enables researchers to prepare and design advanced materials in a more rational way and facilitates them to explore more cutting-edge energy storage materials. Finally, two effective techniques including heteroatom doping and composite material construction are reviewed to address the general problem of low supercapacitor energy density. This review demonstrates the great potential of biomass porous carbon with superior properties, provides advanced tailoring and design viewpoints for the application fields of high-performance supercapacitors, and is expected to inspire new exploration and boost the practical commercial applications of biomass-derived hierarchical porous carbon material in more energy storage and conversion fields.

Preparation of oxygen-rich porous carbon from low rank coal.

No abstract

Waste powder char (WPC) is harmful to the environment and is abundant in the production process of the coal chemical industry, which will produce relatively low heat energy and release large amounts of coal ash if it is burned directly. To efficiently solve this issue and create high values, three-dimensional hierarchical porous carbons (HPCs) with abundant oxygen-containing groups were prepared by collaborative pyrolysis carbonization and steam activation from Yulin bitumite (YL) mixed with WPC. The effects of preparation parameters including WPC doping amount, activation temperature, and activation time on pore structure development and adsorption capacity of methylene blue from wastewater were explored in detail. The obtained HPCs are micropores structure combined with mesopores and the largest specific surface area (SSA) is reached to 1299.75 m2g− 1 (8-YLHPC-950-3). Furthermore, 8-YLHPC-900-3 presents a high oxygen content reaches 15.92wt%. And the SSA and total pore volume of HPC with an 8wt% WPC doping ratio are larger than that without WPC doping. Meanwhile, HPCs show the superior adsorption performance of methylene blue in aqueous solution, especially when the HPC was prepared at the activation temperature of 900 ℃, steam flow of 0.8 mLg− 1h− 1, and activation time of 3 h. It presents the optimal adsorption capacity that is 301 mgg− 1 of methylene blue adsorption value (MBV). We conclude a value-added utilization approach for coal based solid waste and a potential feedstock for adsorption material used in the purification of wastewater. The results achieved in this study provide a green and environmentally friendly method for the preparation of HPCs from waste powder char which is not only an industrial reference for the removal of methylene blue from wastewater by HPCs but also contributes to the sustainable development of the coal chemical industry.