Maria-Magdalena Titirici

Engineering Carbon Materials from the Hydrothermal Carbonization Process of Biomass

Energy shortage, environmental crisis, and developing customer demands have driven people to find facile, low-cost, environmentally friendly, and nontoxic routes to produce novel functional materials that can be commercialized in the near future. Amongst various techniques, the hydrothermal carbonization (HTC) process of biomass (either of isolated carbohydrates or crude plants) is a promising candidate for the synthesis of novel carbon-based materials with a wide variety of potential applications. In this Review, we will discuss various synthetic routes towards such novel carbon-based materials or composites via the HTC process of biomass. Furthermore, factors that influence the carbonization process will be analyzed and the special chemical/physical properties of the final products will be discussed. Despite the lack of a clear mechanism, these novel carbonaceous materials have already shown promising applications in many fields such as carbon fixation, water purification, fuel cell catalysis, energy storage, CO(2) sequestration, bioimaging, drug delivery, and gas sensors. Some of the most promising examples will also be discussed here, demonstrating that the HTC process can rationally design a rich family of carbonaceous and hybrid functional carbon materials with important applications in a sustainable fashion.

Superior Storage Performance of a Si@SiOx/C Nanocomposite as Anode Material for Lithium-Ion Batteries

Rechargeable lithium-ion batteries are essential to portable electronic devices. Owing to the rapid development of such equipment there is an increasing demand for lithium-ion batteries with high energy density and long cycle life. For high energy density, the electrode materials in the lithium-ion batteries must possess high specific storage capacity and coulombic efficiency. Graphite and LiCoO2 are normally used and have high coulombic efficiencies (typically >90%) but rather low capacities (372 and 145 mAhg, respectively).[1–5] Various anode materials with improved storage capacity and thermal stability have been proposed for lithium-ion batteries in the last decade. Among these, silicon has attracted great interest as a candidate to replace commercial graphite materials owing to its numerous appealing features: it has the highest theoretical capacity (Li4.4Sio4200 mAhg) of all known materials, and is abundant, inexpensive, and safer than graphite (it shows a slightly higher voltage plateau than that of graphite as shown in Figure S1, and lithiated silicon is more stable in typical electrolytes than lithiated graphite[6]).

Nitrogen‐Containing Hydrothermal Carbons with Superior Performance in Supercapacitors

[ ∗] L. Zhao , Prof. M. Antonietti , Dr. M.-M. Titirici Colloid Chemistry Department Max-Planck Institute for Colloids and Interfaces Am Muehlenberg 1, 14424 Potsdam (Germany) E-mail: Magdalena.Titirici@mpikg.mpg.de Prof. L.-Z. an , F M.-Q. Zhou , H. Guan , Qiao S. . YSchool of Materials Science and Engineering University of Science and Technology Beijing 100083 Beijing (China) E-mail: fanlizhen@ustb.edu.cn L. Zhao Institute of Coal Chemistry Chinese Academy of Sciences 27th Taoyuan South Road, 030001 Taiyuan (China)

Hydrothermal carbonization of biomass residuals: a comparative review of the chemistry, processes and applications of wet and dry pyrolysis

The carbonization of biomass residuals to char has strong potential to become an environmentally sound conversion process for the production of a wide variety of products. In addition to its traditional use for the production of charcoal and other energy vectors, pyrolysis can produce products for environmental, catalytic, electronic and agricultural applications. As an alternative to dry pyrolysis, the wet pyrolysis process, also known as hydrothermal carbonization, opens up the field of potential feedstocks for char production to a range of nontraditional renewable and plentiful wet agricultural residues and municipal wastes. Its chemistry offers huge potential to influence product characteristics on demand, and produce designer carbon materials. Future uses of these hydrochars may range from innovative materials to soil amelioration, nutrient conservation via intelligent waste stream management and the increase of carbon stock in degraded soils.

Chemistry and materials options of sustainable carbon materials made by hydrothermal carbonization

The production of functional nanostructured materials starting from cheap natural precursors using environmentally friendly processes is a highly attractive subject in material chemistry today. Recently, much attention has been focused on the use of plant biomass to produce functional carbonaceous materials, encompassing economic, environmental and social issues. Besides the classical route to produce activated carbons from agricultural side products, the hydrothermal carbonization (HTC) process shows clear advantages in that it can generate a variety of cheap and sustainable carbonaceous materials with attractive nanostructure and functionalization patterns for a wide range of applications. In this tutorial review we present the latest developments in this traditional but recently invigorated technique. It will be shown that HTC does not only access carbonaceous materials under comparatively mild hydrothermal conditions, but also replaces the more technical and structurally well-defined charring by a controlled chemical process. It will be shown that this makes it possible to tailor the final structure with the tools of colloid and polymer science, leading to very different morphologies with miscellaneous applications, including modern carbon nanocomposites and hybrids.

One‐Step Solvothermal Synthesis of a Carbon@TiO2 Dyade Structure Effectively Promoting Visible‐Light Photocatalysis

The development of sunlight harvesting chemical systems to catalyze relevant reactions, i.e., water splitting, CO 2 fi xation, and organic mineralization, is the key target in artifi cial photosynthesis but remains a diffi cult challenge. Titanium dioxide (TiO 2 ) has been widely used as a photocatalyst for solar energy conversion and environmental applications because of its low toxicity, abundance, high photostability, and high effi ciency. [ 1–4 ] However, the application of pure TiO 2 is limited, because it requires ultraviolet (UV) light, which makes up only a small fraction ( < 4%) of the total solar spectrum reaching the surface of the earth. Therefore, over the past few years, considerable efforts have been directed towards the improvement of the photocatalytic effi ciency of TiO 2 in the visible (vis)-light region. [ 5–7 ] This has been mainly achieved by introducing various dopants into the TiO 2 structure which can narrow the bandgap. The initial approach to dope TiO 2 materials was achieved using transition metals ions such as V, Cr, or Fe. [ 6 , 8–10 ] However, such metal doped materials lack the necessary thermal stability, exhibit atom diffusion and a remarkably increased electron/hole recombination of defect sites, which results in a low photocatalytic effi ciency. [ 11 ] Non-metal doping has since proved to be far more successful and has been extensively investigated. Thus, numerous reports on TiO 2 doped with B, F, N, C, S, or I have demonstrated a signifi cant improvement of the visible-light photocatalytic effi ciency. [ 4 , 12–16 ]

Back in the black: hydrothermal carbonization of plant material as an efficient chemical process to treat the CO2 problem?

A chemical process, hydrothermal carbonization (HTC) of low value biomass, is discussed as a tool for the sequestration of atmospheric CO2. Via the available biomass, CO2 can be transformed into an efficient deposited form of carbon, i.e. hardly degradable peat or carbonaceous soil.

Functional hollow carbon nanospheres by latex templating.

A facile and sustainable synthesis of hollow carbonaceous nanospheres is presented, offering a scalable and multifunctional route to the generation of useful nanocontainers, which critically possess the stability not offered by polymeric equivalents and functionality not afforded by other nanocarbons. Carbonization temperature provides a subtle but elegant mechanism to control structure and thereby hydrophobicity, nanopartitioning, and permeation between the inner and outer space.

Topological Defects in Metal-Free Nanocarbon for Oxygen Electrocatalysis.

A bifunctional graphene catalyst with abundant topological defects is achieved via the carbonization of natural gelatinized sticky rice to probe the underlying oxygen electrocatalytic mechanism. A nitrogen-free configuration with adjacent pentagon and heptagon carbon rings is revealed to exhibit the lowest overpotential for both oxygen reduction and evolution catalysis. The versatile synthetic strategy and novel insights on the activity origin facilitate the development of advanced metal-free carbocatalysts for a wide range of electrocatalytic applications.

Carbohydrate-Derived Hydrothermal Carbons: A Thorough Characterization Study

Hydrothermal carbonization (HTC) is an aqueous-phase route to produce carbon materials using biomass or biomass-derived precursors. In this paper, a comprehensive physicochemical and textural characterization of HTC materials obtained using four different precursors, namely, xylose, glucose, sucrose, and starch, is presented. The development of porosity in the prepared HTC materials as a function of thermal treatment (under an inert atmosphere) was specifically monitored using N(2) and CO(2) sorption analysis. The events taking place during the thermal treatment process were studied by a combined thermogravimetric/infrared (TGA-IR) measurement. Interestingly, these inexpensive biomass-derived carbon materials show good selectivity for CO(2) adsorption over N(2) (CO(2)/N(2) selectivity of 20 at 273 K, 1 bar and 1:1 gas composition). Furthermore, the elemental composition, morphologies, degree of structural order, surface charge, and functional groups are also investigated.