Levulinic acid is a sustainable platform molecule that can be upgraded to valuable chemicals and fuel additives. This article focuses on the catalytic upgrading of levulinic acid into various ...chemicals such as levulinate esters, δ‐aminolevulinic acid, succinic acid, diphenolic acid, γ‐valerolactone, and γ‐valerolactone derivatives such valeric esters, 5‐nonanone, α‐methylene‐γ valerolactone, and other various molecular‐weight alkanes (C9 and C18–C27 olefins).
Refined and ready: Lignocellulosic biomass upgrade through the use of levulinic acid offers a wide array of products with a variety of applications ranging from fuel additives to biobased chemicals, green solvents, biopolymers, and biofertilizers.
The aqueous oxygen reduction reaction (ORR) has recently received increased attention due to its critical role in clean and sustainable energy‐generation technologies, such as proton exchange ...membranes (PEM) fuel cells, alkaline fuel cells and Zn–air batteries. The sluggish kinetics associated with ORR result from multistep electron‐transfer process. The slow kinetics are partially related to the O2 adsorption process onto the catalyst, which happens at the triple‐phase boundary (TPB) of the electrocatalyst–electrolyte–oxygen interface. Hence, tremendous efforts have been devoted to improving the intrinsic properties of electrocatalysts such as active sites, electrical conductivity and porosity. Engineering the electrocatalyst's interfacial properties is another critical issue in ORR, however less described in the literature. The surface of the catalyst provides the microenvironment for the triple boundary interface reaction, which directly influences its electrocatalytic activity and the kinetics. This Minireview is a summary of the existing literature on manipulating the interfacial surface of non‐precious metal catalysts at the triple point between the solid catalyst, the aqueous electrolyte and the O2 gas with the aim of improving the ORR efficiency. Various approaches towards improving the wettability and nanostructuring the catalyst surface to boost the activity of the surface‐active sites and provide improved stability are discussed.
Promoting adsorption: The sluggish kinetics resulting from multistep electron transfer processes is the main concern in ORR. Promoting O2 adsorption, which happens on the triple‐phase boundary (TPB) of electrocatalyst–electrolyte–oxygen interface can overcome the slow kinetics. In this paper we review some of the existing surface engineering strategies in the literature aiming to manipulate the triple point boundary (TPB) to promote the aqueous ORR.
A deeper understanding of the water‐splitting hydrogen evolution reaction (HER) mechanism during photocatalytic processes is crucial for the rational design of efficient photocatalysts. In ...particular, the HER mechanism promoted by multielement hybrid structures remains extremely challenging and elusive. Herein, an in situ photoelectrochemical/Raman measurement system is employed to monitor the HER mechanism of hybrid nanostructures under realistic working conditions via operando Raman spectra and linear‐sweep voltammetry curves. As a proof of concept, tunable composition transition metal dichalcogenides MoS2xSe2(1−x) nanosheets are used as a model photocatalyst to unveil the corresponding photocatalytic mechanism. The spectroscopic studies reveal that hydrogen atoms can be adsorbed to active sulfur and selenium atoms via intermediate species formed during the photocatalytic process. More importantly, the studies demonstrate that an exponential relationship exists between the number of reactive electrons and the Raman intensity of intermediate species, which can serve as a guideline to directly evaluate the HER performance in photocatalysts by comparing the Raman intensities of the intermediate species. As a simple, intuitive, and general analytical method, the designed operando Raman measurement approach provides a new tool for elucidating catalytic reaction mechanisms in a realistic and complex environment; and strategically improving H2 production performance of multielement photocatalysts.
A photoelectrochemical‐operando Raman spectroscopy system is employed to reveal the photocatalytic hydrogen evolution reaction intermediates under practical reaction conditions. An exponential function relationship between the quantity of reactive electrons and the Raman intensity of intermediate species is established, which can serve as a guideline to directly evaluate the catalytic performance, and strategically improve hydrogen production performance of multielement photocatalysts.
Sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs) are prospective candidates for large‐scale energy storage systems cause of their abundant resources. However, unsatisfactory rate and ...cycling performance of carbon‐based anodes present a bottleneck for the applications of SIBs/PIBs due to the large sizes of sodium/potassium ions. Herein, oxygen‐doped vertically aligned carbon aerogels (VCAs) with hierarchically tailored channels are synthesized as anodes in SIBs/PIBs via a controllable unidirectional ice‐templating technique. VCA‐3 (cooling rate of 3 K min−1) delivers the highest reversible capacity of ≈298 mAh g−1 at 0.1 C with an excellent cycling performance over 2000 cycles at 0.5 C for SIBs, while VCA‐5 manifests a superior capacity of ≈258 mAh g−1 at 0.1 C with an 82.7% retention over 1000 cycles at 0.5 C for PIBs. Moreover, their full cells demonstrate the promising potential of VCAs in applications. This novel controllable ice‐templating strategy opens unique avenues to tune the construction of hollow aligned channels for shortening ion‐transport pathways and ensuring structural integrity. New insights into structure‐performance correlations regulated by the cooling rates of an ice‐templating strategy and design guidelines for electrodes applicable in multiple energy storage technologies are reported.
A novel controllable ice‐templating strategy is utilized to tailor low‐cost cellulose nanocrystal/polyethylene oxide‐derived, vertically aligned carbon aerogels (VCAs) as anodes of sodium‐ and potassium‐ion batteries. The construction of hierarchically tailored channels is tuned for shortening ion‐transport pathways and ensuring structural integrity. These sustainable VCAs can be easily extended to multiple energy storage systems, demonstrating their universal potential.
Biomass is recognized as an ideal CO2 neutral, abundant, and renewable resource substitute to fossil fuels. The rich proton content in most biomass derived materials, such as ethanol, ...5‐hydroxymethylfurfural (HMF) and glycerol allows it to be an effective hydrogen carrier. The oxidation derivatives, such as 2,5‐difurandicarboxylic acid from HMF, glyceric acid from glycerol are valuable products to be used in biodegradable polymers and pharmaceuticals. Therefore, combining biomass‐derived compound oxidation at the anode and hydrogen evolution reaction at the cathode in a biomass electrolysis or photo‐reforming reactor would present a promising strategy for coproducing high value chemicals and hydrogen with low energy consumption and CO2 emissions. This review aims to combine fundamental knowledge on photo and electro‐assisted catalysis to provide a comprehensive understanding of the general reaction mechanisms of different biomass‐derived molecule oxidation. At the same time, catalyst requirements and recent advances for various feedstock compounds are also reviewed in detail. Technoeconomic assessment and life cycle analysis are performed on various feedstocks to assess the relative benefits of various processes, and finally critical prospects are given on the challenges and opportunities for technology development to meet the sustainability requirement of the future global energy economy.
This review summarizes recent research progress in photo‐ and electrochemical oxidation of biomass feedstocks for the production of chemicals and hydrogen. High‐level technoeconomic assessment and life cycle analysis are performed to evaluate the economic value and environmental impact of biomass electrolysis. Based on the outcomes, perspectives on current technical challenges and future opportunities are provided.
Nanocarbons are of progressively increasing importance in energy electrocatalysis, including oxygen reduction, oxygen evolution, hydrogen evolution, CO2 reduction, etc. Precious-metal-free or ...metal-free nanocarbon-based electrocatalysts have been revealed to potentially have effective activity and remarkable durability, which is promising to replace precious metals in some important energy technologies,such as fuel cells, metal–air batteries, and water splitting. In this review, rather than overviewing recent progress completely, we aim to give an in-depth digestion of present achievements, focusing on the different roles of nanocarbons and material design principles. The multifunctionalities of nanocarbon substrates（accelerating the electron and mass transport, regulating the incorporation of active components,manipulating electron structures, generating confinement effects, assembly into 3 D free-standing electrodes） and the intrinsic activity of nanocarbon catalysts（multi-heteroatom doping, hierarchical structure,topological defects） are discussed systematically, with perspectives on the further research in this rising research field. This review is inspiring for more insights and methodical research in mechanism understanding, material design, and device optimization, leading to a targeted and high-efficiency development of energy electrocatalysis.
A series of hard–soft carbon composite materials is produced from biomass and oil waste and applied as low‐cost anodes for sodium‐ion batteries to study the fundamentals behind the dependence of Na ...storage on their structural features. A good reversible capacity of 282 mAh g−1 is obtained at a current density of 30 mA g−1 with a high initial Coulombic efficiency of 80% at a carbonization temperature of only 1000 °C by adjusting the ratio of hard to soft carbon. The performance is superior to the pure hard or soft carbon anodes produced at the same temperatures. This synergy between hard and soft carbon resulting in an excellent performance is due to the blockage of some open pores in hard carbon by the soft carbon, which suppresses the solid electrolyte interface formation and increases the reversible sodium storage capacity.
A series of hard–soft carbon composite materials is synthesized and it is found that at a low carbonization temperature of 1000 °C, it could show a synergistic effect due to the blockage of open pores. The correlations between structure and sodium storage performances and sodium storage mechanism are also investigated.
Hydrothermal carbonization is a powerful way to convert cellulosic waste into valuable platform chemicals and carbonaceous materials. In this study, to optimize the process, fructose was chosen as ...the carbon precursor and the influence of reaction time, acid catalysis, feed gas and pressure on the conversion products is evaluated. 5‐hydroxymethylfurfural (HMF) is produced in high amounts in relatively short time. Both strong and weak acids accelerate fructose conversion. Levulinic acid (LevA) formation is faster than that of hydrothermal (HT) carbon in acidic conditions. Strong acid catalysts should be considered to target preferentially LevA production, whereas milder conditions should be preferred for HMF production. Moreover, a slight initial overpressure of the reactor is always beneficial in terms of conversion. FT‐IR and 13C ss‐NMR spectroscopy and SEM showed that HT carbon evolves through time from a furanic‐based structure with alkylic linkers to an increasingly cross‐linked condensed structure. MALDI‐ToF mass spectrometry showed the existence of a series of oligomers in a mass range within 650 Da and 1500 Da formed by condensation of repeating units.
The complex interplay between chemical species formed during hydrothermal conversion of fructose is elucidated by several characterization techniques. Reaction time and acid catalysis play major roles in the dehydration of fructose to HMF. A family of newly identified oligomers (mass=600–1500 Da) provides new insights in the intricate hydrothermal carbon formation mechanism.
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