Global warming, environmental pollution, and an energy shortage in the current fossil fuel society may cause a severe ecological crisis. Storage and conversion of renewable, dispersive and non-perennial energy from the sun, wind, geothermal sources, water, or biomass could be a promising option to relieve this crisis. Carbon materials could be the most versatile platform materials applied in the field of modern energy storage and conversion. Conventional carbon materials produced from coal and petrochemical products are usually energy intensive or involve harsh synthetic conditions. It is highly desired to develop effective methods to produce carbon materials from renewable resources that have high performance and limited environmental impacts. In this regard, biochar, a bio-carbon with abundant surface functional groups and easily tuned porosity produced from biomass, may be a promising candidate as a sustainable carbon material. Recent studies have demonstrated that biochar-based materials show great application potential in energy storage and conversion because of their easily tuned surface chemistry and porosity. In this review, recent advances in the applications of biochar-based materials in various energy storage and conversion fields, including hydrogen storage and production, oxygen electrocatalysts, emerging fuel cell technology, supercapacitors, and lithium/sodium ion batteries, are summarized, highlighting the mechanisms and open questions in current energy applications. Finally, contemporary challenges and perspectives on how biochar-based materials will develop and, in particular, the fields in which the use of biochar-based materials could be expanded are discussed throughout the review. This review demonstrates significant potential for energy applications of biochar-based materials, and it is expected to inspire new discoveries to promote practical applications of biochar-based materials in more energy storage and conversion fields.

Emerging applications of biochar-based materials for energy storage and conversion

Currently, electromagnetic (EM) pollution poses severe complication toward the operation of electronic devices and biological systems. To this end, it is pertinent to develop novel microwave absorbers through compositional and structural design. Porous carbon (PC) materials demonstrate great potential in EM wave absorption due to their ultralow density, large surface area, and excellent dielectric loss ability. However, the large-scale production of PC materials through low-cost and simple synthetic route is a challenge. Deriving PC materials through biomass sources is a sustainable, ubiquitous, and low-cost method, which comes with many desired features, such as hierarchical texture, periodic pattern, and some unique nanoarchitecture. Using the bio-inspired microstructure to manufacture PC materials in mild condition is desirable. In this review, we summarize the EM wave absorption application of biomass-derived PC materials from optimizing structure and designing composition. The corresponding synthetic mechanisms and development prospects are discussed as well. The perspective in this field is given at the end of the article.

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Biomass-Derived Porous Carbon-Based Nanostructures for Microwave Absorption

Metal-Organic Frameworks for Batteries

Over the past two decades, metal-organic frameworks (MOFs), a type of porous material, have aroused great interest as precursors or templates for the derivation of metal oxides and composites for the next generation of electrochemical energy storage applications owing to their high specific surface areas, controllable structures, and adjustable pore sizes. The electrode materials, which affect the performance in practical applications, are pivotal components of batteries and supercapacitors. Metal oxide composites derived from metal-organic frameworks possessing high reversible capacity and superior rate and cycle performance are excellent electrode materials. In this Review, potential applications for MOF-derived metal oxide composites for lithium-ion batteries, sodium-ion batteries, lithium-oxygen batteries, and supercapacitors are studied and summarized. Finally, the challenges and opportunities for future research on MOF-derived metal oxide composites are proposed on the basis of academic knowledge from the reported literature as well as from experimental experience.

Youyu Zhu

Papers

A porous biomass-derived anode for high-performance sodium-ion batteries

A biomass-derived nitrogen-doped porous carbon for high-energy supercapacitor

Commercial activated carbon as a novel precursor of the amorphous carbon for high-performance sodium-ion batteries anode

High-yield humic acid-based hard carbons as promising anode materials for sodium-ion batteries

A novel room temperature ethanol gas sensor based on 3D hierarchical flower-like TiO2 microstructures