Carbon Substrate Research Articles

Understanding the Curvature Effect on the Structure and Bonding of MoCy Nanoparticles on Carbon Supports.

The interaction between molybdenum carbide (MoCy) nanoparticles and both flat and curved graphene surfaces, serving as models for carbon nanotubes, was investigated by means of density functional theory. A variety of MoCy nanoparticles with different sizes and stoichiometries have been used to explore different adsorption sites and modes across models with different curvature degrees. On flat graphene, off-stoichiometric MoCy featuring more low-coordinated Mo atoms exhibits stronger interaction and increased electron transfers from the carbide to the carbon substrate. This preferentially occurs through support C and Mo atoms leading to the formation of additional Mo-C bonds. Notably, the MoCy adsorption strength increases on concave surfaces and decreases on convex surfaces, showing a strong linear correlation with the surface curvature. This curvature-dependent behavior alters the charge state of the nanoparticles, making them more/less positively charged in concave/convex regions. The present results demonstrate that the interaction strength can be effectively tuned by manipulating the carbide stoichiometry, the substrate curvature, and the local concave/convex environments, providing valuable guidelines for the rational design of MoCy/C-based catalysts.

The edaphic factor and orchids: Gymnadenia conopsea from contrasting geologies in the Central Balkans.

Two different strategies for the distribution of macro- and trace elements can be observed in the terrestrial orchid Gymnadenia conopsea. Most trace elements are not translocated to the above-ground parts, whereas for macro-elements the trend was reversed, with the highest accumulation in the distal parts of the plants. Edaphic stress is one of the main factors affecting plant fitness, but it is still poorly understood, even in rare plants such as orchids. Gymnadenia conopsea is a terrestrial orchid that grows on different geological substrates, making it a model species for the study of adaptive responses to edaphic factors, including metals in soil. The samples of plant tissues of G. conopsea growing on carbonate, ultramafic and siliceous substrates in Serbia and the associated rhizosphere soil were collected and analysed for elemental concentrations. Two different strategies for the distribution of macro- and trace elements were found, corresponding to the trend generally observed in orchids. Trace elements (As, B, Cr, Co, Fe, Mn, and Ni) remain mainly in the underground organs and only a small proportion is transferred to the shoots. It was the opposite for the macroelements (Ca, Mg, K and P) with the highest accumulation occurred in the leaves and inflorescences. The tolerance of G. conopsea to the different geological substrates results from the moderate metal concentrations in the soils analysed and the exclusion strategy of the species, which is the most common response to metal induced stress in orchids.

Root productivity contributes to carbon storage and surface elevation adjustments in coastal wetlands

Abstract Background and aims Organic matter additions in coastal wetlands contribute to blue carbon sequestration and adjustment to sea-level rise through vertical substrate growth, with accurate modelling of these dynamics requiring information of root mass and volume additions across tidal gradients. This study aims to characterise the influence of vegetation zonation and tidal position on root mass and volume dynamics within substrates. Methods The root ingrowth technique was coupled with sediment cores to quantify below-ground root mass and volume production, standing stocks and turnover across two years to 90 cm depth at Kooweerup, Victoria, Australia. Results We indicate a complex non-linear relationship between fine root mass production and tidal position, influenced by variable vegetation structures across mangrove (442–3427 g m−2 yr−1), saltmarsh (540–860 g m−2 yr−1) and supratidal forest (599 g m−2 yr−1) zones. Fine root volume additions ranged from 274 to 4055 cm3 m−2 yr−1 across sampling locations. Root production was greatest for older mangroves and tidally defined optimal zones of production were evident for mangrove and saltmarsh. Live roots extended deeper than typically studied, reaching depths of 1.0 m in forested zones. Conclusion This information of root mass and volume additions across wetland live rooting zones can be used to improve highly parameterised models accounting for carbon sequestration and substrate vertical adjustment along intertidal gradients. We recommend that future studies measure root production across the entire active rooting zone or to 1 m depth to align with standard carbon accounting measurement depths.

Boosting the Hydrogen Evolution Activity of a Low-Coordinated Co─N─C Catalyst via Vacancy Defect-Mediated Alteration of the Intermediate Adsorption Configuration.

The cobalt-nitrogen-carbon (Co─N─C) single-atom catalysts (SACs) are promising alternatives to precious metals for catalyzing the hydrogen evolution reaction (HER) and their activity is highly dependent on the coordination environments of the metal centers. Herein, a NaHCO3 etching strategy is developed to introduce abundant in-plane pores within the carbon substrates that further enable the construction of low-coordinated and asymmetric Co─N3 sites with nearby vacancy defects in a Co─N─C catalyst. This catalyst exhibits a high HER activity with an overpotential (η) of merely 78mV to deliver a current density of 10mA cm-2, a Tafel slope of 45.2mV dec-1, and a turnover frequency of 1.67 s-1 (at η = 100mV). Experimental investigations and theoretical calculations demonstrate that the vacancy defects neighboring the Co─N3 sites can modulate the electronic structure of the catalyst and alter the adsorption configuration of the H intermediate from the typical atop mode to the side mode, resulting in weakened H adsorption strength and thus improved HER activity. This work provides an efficient strategy to regulate the coordination environment of SACs for improved catalytic performance and sheds light on the atomic-level understanding of the structure-activity relationships.

Nanozymes with Modulable Inhibition Transfer Pathways for Thiol and Cell Identification.

The elementary mechanism and site studies of nanozyme-based inhibition reactions are ambiguous and urgently require advanced nanozymes as mediators to elucidate the inhibition effect. To this end, we develop a class of nanozymes featuring single Cu-N catalytic configurations and B-O sites as binding configurations on a porous nitrogen-doped carbon substrate (B6/CuSA) for inducing modulable inhibition transfer at the atomic level. The full redistribution of electrons across the Cu-N sites, induced by B-O sites incorporation, yields B6/CuSA with enhanced peroxidase-like activity versus CuSA. More importantly, CuSA with single Cu-N sites features in cysteine binding and expresses a competitive inhibition through coordination bonds, with an inhibition constant of 0.048 mM. Benefiting from the modulable binding way in nanozymes, B6/CuSA possesses mixed binding approaches for cysteine through noncovalent bonds and delivers a record-mixed inhibition interaction with a competitive inhibition constant of 0.054 mM and a noncompetitive inhibition constant of 0.71 mM. Based on the modulable inhibition of B6/CuSA and CuSA, a multichannel sensor array accomplishes the detection of various cancer cells, normal cells, and thiols. The design principle of this work is endowed with guidelines for the preliminary inhibition mechanism evaluation of massive potential thiols, cell discrimination, and disease prediction.

Ionic-Liquid Synthesis of Atomic Molybdenum Nitride Clusters as Bifunctional Oxygen Reduction and Evolution Reactions Electrocatalysts for Alkaline Zn-Air Battery.

Transition-metal nitrides (TMNs) have garnered considerable attention for energy conversion applications owing to their exceptional electronic structures and high catalytic activities. However, the scarcity of active sites in TMNs impedes their large-scale application. This study describes the use of wetness impregnation and ionic-liquid methods to enhance the electrocatalytic efficiency of molybdenum nitride (MoN) atomic clusters finely dispersed on nitrogen-doped carbon (MoN@NC) substrates. The as-synthesized electrocatalysts feature atomically dispersed MoN clusters, achieving an impressive onset potential of 0.93 V vs. RHE for the oxygen reduction reaction (ORR) and maintaining an overpotential of just 295 mV at a current density of 10 mA/cm2 for the oxygen evolution reaction (OER). The MoN@NC-based zinc-air battery demonstrated a high-power density of 151 mW/cm2, a robust specific discharge capacity of 759 mAh/gZn at 20 mA/cm2, and superior charge-discharge cycling stability exceeding 190 cycles. The detailed experimental characterization revealed that the uniformly dispersed MoN clusters served as the primary active sites driving the observed catalytic performance. Additionally, the present findings suggested significant correlations between the phase of the material, crystallization, atomic cluster distribution, support porosity, and nitridation temperature. These insights are expected to refine strategies for achieving atomically dispersed nitrides with optimized ORR performance.

Laser Synthesis of Platinum Single-Atom Catalysts for Hydrogen Evolution Reaction.

Platinum (Pt)-based heterogeneous catalysts show excellent performance for the electrocatalytic hydrogen evolution reaction (HER); however, the high cost and earth paucity of Pt means that efforts are being directed to reducing Pt usage, whilst maximizing catalytic efficiency. In this work, a two-step laser annealing process was employed to synthesize Pt single-atom catalysts (SACs) on a MOF-derived carbon substrate. The laser irradiation of a metal-organic framework (MOF) film (ZIF67@ZIF8 composite) by rapid scanning of a ns pulsed infrared (IR; 1064 nm) laser across the freeze-dried MOF resulted in a metal-loaded graphitized film. This was followed by loading this film with chloroplatinic acid (H2PtCl6), followed by further irradiation with an ultraviolet (UV; 355 nm) laser, resulting in pyrolysis of H2PtCl6 to form the SAC, along with a further reduction of the MOF to form a Pt-decorated laser-induced annealed MOF (Pt-LIA-ZIF8@ZIF67). The Pt-LIA-ZIF8@ZIF67 catalyst with a Pt loading of 0.86 wt. % exhibited exceptionally high activity for the HER in acidic conditions. The atomically dispersed Pt on the carbon substrate exhibited a small overpotential of 68.8 mV at 10 mA cm-2 for the hydrogen evolution reaction with a mass activity 20.52 times that of a commercial Pt/C catalyst at an overpotential of 50 mV vs. RHE. Finally, we note that the synthesis method is simple, fast, and versatile, and potentially scalable for the mass production of SACs for electrocatalytic applications.

The preparation of Fe, N Co-doped ZIF-derived carbon nanosheet catalysts for oxygen reduction electrocatalyst in zinc-air batteries

A co-doping approach involving transition metals and heteroatoms was employed to successfully synthesize carbon nanosheet catalysts co-doped with iron (Fe) and nitrogen (N). Employing ferrous sulfate as the Fe source, ZIF-8 as the carbon substrate, 1,10-phenanthroline as the metal chelating agent and nitrogen source, Fe2+ can automatically adhere to the ZIF-8 N-doped carbon nanosheets under the chelation of 1,10-phenanthroline. After pyrolysis, Fe is successfully incorporated into the carbon matrix, the generation of numerous ORR active sites, Fe-Nx, are formed, enhancing the ORR catalytic efficiency. In alkaline solutions, the synthesized Fe-NCF-2 catalyst exhibits excellent ORR electrocatalytic activity compared to commercial Pt/C (20 wt% Pt). The ZAB assembled with Fe-NCF-2 as the air cathode demonstrates outstanding performance. This provides an economically viable preparation strategy for exploring efficient catalysts for the ORR.

ZIF-8-derived Fe/P/N-co-doped carbon as efficient electrocatalysts for oxygen reduction reaction and zinc–air batteries

A facile method for preparing P-doped Fe–N–C catalysts for zinc–air batteries. The effect of P atoms on both Fe–Nx active sites and carbon substrates enhances catalytic activity.

Acidogenic fermentation of dairy by-products for the utilization of volatile fatty acids IN PHBV production by Haloferax mediterranei

Acidogenic fermentation of cheese whey was performed to obtain streams rich in volatile fatty acids, which were successfully used as carbon substrates to biosynthesize polyhydroxyalcanoates by the bacterial strain Haloferax mediterranei.

Uniformly dispersing Sb2Se3 nanoparticles in porous carbon as an anode material for enhancing sodium storage capacity.

About 60 nm Sb2Se3 nanoparticles are uniformly embedded in a porous carbon substrate to prepare a Sb2Se3/C composite through a combination of pyrolysis reduction and solid-phase selenization. The Sb2Se3/C anode exhibits excellent sodium storage capacity. The initial discharge capacity is up to 420 mA h g-1 at 0.1 A g-1, and the specific capacity still remains 339 mA h g-1 after 1000 cycles, with a high capacity retention rate of 80%.

Electronic Promoter Breaks the Linear Scaling Relationship: Ultra‐Rapid High‐Temperature Synthesis of Heterostructured CoS/SnO2@C as a Bifunctional Oxygen Catalyst for Li‐O2 Batteries

AbstractLi‐O2 batteries urgently needs high discharge capacity and stable cycling performance, requiring effective and reliable bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Hovenia acerba Lindl‐like heterostructure composed of cobalt sulfide and tin dioxide supported on carbon substrate (CoS/SnO2@C) is prepared via CO2 laser irradiation technology. The half‐wave potential of CoS/SnO2@C for the ORR is 0.88 V, while the overpotential of the OER at 10 mA cm−2 is as low as 270 mV. The Li‐O2 batteries employing the bifunctional CoS/SnO2@C catalyst displays a high discharge specific capacity of 3332.25 mAh g−1 and long cycling life of 226 cycles. Additionally, theory calculations demonstrate that the construction of heterostructure decreases energy barrier of the rate‐determining step (RDS) for both ORR and OER. Notably, SnO2 behaves as the electronic promoter to optimize the electronic structure of heterostructure interface and triggers charge redistribution of CoS, which weakens the adsorption strength of the *O‐intermediates and allows to break the linear scaling relationship, thus further enhancing the catalytic performance of CoS/SnO2@C. This research furnishes directions for the design of heterogeneous catalysts, highlighting its great potential for application in rechargeable Li‐O2 batteries.

Converting multiple hydrophobic aromatic plastic monomers into a single water-soluble substrate to increase bioavailability for the synthesis of polyhydroxyalkanoates by bacteria using batch, fed batch and continuous cultivation.

We demonstrate the proof of concept of increasing the bioavailability of carbon substrates, derived from plastic waste, for their conversion to the biodegradable polymer polyhydroxyalkanoate [PHA] by bacteria and test various approaches to PHA accumulation through batch, fed batch and continuous culture. Styrene, ethylbenzene, and toluene are produced from the pyrolysis of mixed plastic waste (Kaminsky, 2021; Miandad et al., 2017), but they are volatile and poorly soluble in water making them difficult to work with in aqueous fermentation systems. By chemically converting these aromatic compounds to benzoic acid, and subsequently to its sodium salt, we increased the solubility and reduced the volatility of the substrate supplied to Pseudomonas putida CA-3 to accumulate polyhydroxyalkanoates. 1L scale batch, fed batch, and continuous fermentations were carried out; the fed batch fermentation resulted in the maximum volumetric PHA productivity of 61.67 ± 7.34mgL-1 h-1; while batch and continuous, at a dilution rate, d = 0.2h-1, fermentations resulted in 13.30 ± 0.01 and 4.06 ± 0.01mgL-1 h-1 of PHA respectively.

Theoretical Study on the Adsorption of Hexavalent Chromium by Metal-Modified and Nitrogen-Doped Carbon Materials.

Cr(VI) can cause great harm to human beings and the environment and often exists in the form of HCrO4̅ in aqueous environments. The adsorption characteristics of HCrO4̅ on nitrogen-doped and iron-nickel-modified carbon substrates were systematically investigated using first principles. The properties of electron transfer and orbital hybridization of the substrates and HCrO4̅ during the adsorption process were analyzed by electron deformation density and density of states. The electrons were donated by the metal atoms and gained by the oxygen atoms involved in the adsorption of HCrO4-. The binding energies of the substrates and metal atoms were larger than the cohesive energies of the metal atoms, indicating excellent structural stability. Both mono- and bimetallic modifications of the carbon materials by Fe/Ni were favorable for the adsorption of HCrO4-. The increased number of doped nitrogen atoms could promote the adsorption. Among them, (Fe,Ni)/N-C possesses the optimal adsorption of HCrO4-, with an adsorption energy of -4.64 eV. This is mainly attributed to the fact that the Fe-Ni bimetallic atoms simultaneously participate in the electron transfer and orbital hybridization, providing a new perspective for the adsorption of Cr(VI) on bimetallic-modified substrates.

Chlorine Axial Coordination Activated Lanthanum Single Atoms for Efficient Oxygen Electroreduction with Maximum Utilization.

Currently, there are still obstacles to rationally designing the ligand fields to activate rare-earth (RE) elements with satisfactory intrinsic electrocatalytic reactivity. Herein, axial coordination strategies and nanostructure design are applied for the construction of La single atoms (La-Cl SAs/NHPC) with satisfactory oxygen reduction reaction (ORR) activity. The nontrivial LaN4Cl2 motifs configuration and the hierarchical porous carbon substrate that facilitates maximized metal atom utilization ensure high half-wave potential (0.91V) and significant robustness in alkaline media. The aqueous and flexible Zinc-air battery (ZAB) integrating La-Cl SAs/NHPC as the cathode catalyst exhibits a maximum power density of 260.7 and 68.5mW cm-2, representing one of the most impressive RE-based ORR electrocatalysts to date. Theoretical calculations have demonstrated that the Cl coordination evidently modulate the electronic structures of La sites, which promoted electron transfer efficiency by d-p orbital couplings. With enhanced electroactivity of La sites, the adsorptions of key intermediates are optimized to alleviate the energy barriers of the potential-determining step. Importantly, this preparation strategy is also successfully applied to other REs. This work provides perspectives for near-range electronic structure modulation of RE-SAs based on a nonplanar coordination micro-environment for efficient electrocatalysis.

2D Carbon-Anchored Platinum-Based Nanodot Arrays as Efficient Catalysts for Methanol Oxidation Reaction.

Ultrafine Pt-based alloy nanoparticles supported on carbon substrates have attracted significant attention due to their catalytic potential. Nevertheless, ensuring the stability of these nanoparticles remains a critical challenge, impeding their broad application. In this work, novel nanodot arrays (NAs) are introduced where superfine alloy nanoparticles are uniformly implanted in a 2D carbon substrate and securely anchored. Electrochemical testing of the PtCo NAs demonstrates exceptional methanol oxidation reaction (MOR) activity, achieving 1.25 A mg-1. Moreover, the PtCo NAs exhibit outstanding stability throughout the testing period, underscoring the effectiveness of the anchoring mechanism. Comprehensive characterization and theoretical calculations reveal that the 2D carbon-anchored structure optimizes the electronic structure and coordination environment of Pt, restricts nanoparticle migration, and suppresses transition metal dissolution. This strategy represents a major advancement in addressing the stability limitations of ultrafine nanoparticles in catalytic applications and offers broader insights into the design of next-generation catalysts with enhanced durability and performance.

Developing an in Situ Polyoxovanadate to Vanadium Nitride/Carbon Conversion Strategies in Manufacture Aqueous Zinc Ion Batteries Cathode with Ultrahigh Rate Capability

AbstractVanadium nitride (VN) is considered to have sufficient application potential for energy storage, and in the field of aqueous zinc‐ion batteries (AZIBs), its unique in situ phase transition mechanism is conducive to solving the intrinsic low conductivity, slow kinetics, and poor cycling stability of vanadium‐based materials. In the present study, the nanoscale morphology of VN cathode materials is controlled by cationic modulation of decavanadate precursors. Among them, VN quantum dots/nitrogen‐doped carbon nanosheets (VNQD/NC), which have the prime particle size and uniform distribution on a carbon substrate, show excellent cathode performance after activation. The innovative VNQD/NC composite exhibits high discharge capacity (698 mAh g−1 at 0.5 A g−1), excellent rate performance (498 mAh g−1 at 20 A g−1), and excellent stability. The mechanism of the VNQD/NC cathode is investigated by various ex situ means, and researchers actively analyze the source of its excellent electrochemical performance. This work offers an alternative strategy for the preparation of nitride materials and provides insights into the development of high‐performance vanadium‐based cathodes for AZIBs.

Trimetallic Atom‐Doped Functional Carbon Catalyst Enables Fast Redox Kinetics and Durable Cyclic Stability of Zinc‐Iodine Batteries

AbstractActive iodine dissolution and polyiodide shuttle are two major obstacles hindering the application of zinc‐iodine batteries (ZIBs). Designing functional carriers with strong physisorption/chemisorption capability, abundant active sites, and high catalytic activity for iodine redox reaction kinetics, is considered an effective strategy to solve the current problems of ZIBs. In this work, Fe, Co, Ni‐doping porous carbon (FeCoNi) is comprehensively investigated as carrier material to prepare the iodine‐loading cathode of FeCoNi@I2. On the basis of experimental tests and theoretical calculations, the introduction of FeCoNi trimetallic atoms effectively regulates the electronic structure, charge distribution, active sites, and electronic conductivity of porous carbon substrate, promoting the iodine conversion reaction kinetics as well as chemisorption capability for iodine species, which is conducive to inhibit the polyiodide shuttle and active iodine dissolution. As expected, Zn//FeCoNi@I2 batteries exhibit high specific capacity and strong self‐discharge resistance capability, and the reversible capacity of FeCoNi@I2 cathode stabilizes at 108.8 mAh g−1 after 13000 cycles at 1 A g−1, and 94.7 mAh g−1 after 14000 cycles at 3 A g−1. This work will open new horizons for the structural design of catalyst‐type carrier materials for durable ZIBs, and facilitate the application of trimetallic atom‐doped porous carbon in high‐performance secondary batteries.

Quantitative physiology and biomass composition of Cyberlindnera jadinii in ethanol-grown cultures

BackgroundElimination of greenhouse gas emissions in industrial biotechnology requires replacement of carbohydrates by alternative carbon substrates, produced from CO2 and waste streams. Ethanol is already industrially produced from agricultural residues and waste gas and is miscible with water, self-sterilizing and energy-dense. The yeast C. jadinii can grow on ethanol and has a history in the production of single-cell protein (SCP) for feed and food applications. To address a knowledge gap in quantitative physiology of C. jadinii during growth on ethanol, this study investigates growth kinetics, growth energetics, nutritional requirements, and biomass composition of C. jadinii strains in batch, chemostat and fed-batch cultures.ResultsIn aerobic, ethanol-limited chemostat cultures, C. jadinii CBS 621 exhibited a maximum biomass yield on ethanol (YX/Smax) of 0.83 gbiomass (gethanol)−1 and an estimated maintenance requirement for ATP (mATP) of 2.7 mmolATP (gbiomass)−1 h−1. Even at specific growth rates below 0.05 h−1, a stable protein content of approximately 0.54 gprotein (gbiomass)−1 was observed. At low specific growth rates, up to 17% of the proteome consisted of alcohol dehydrogenase proteins, followed by aldehyde dehydrogenases and acetyl-CoA synthetase. Of 13 C. jadinii strains evaluated, 11 displayed fast growth on ethanol (μmax > 0.4 h−1) in mineral medium without vitamins, and CBS 621 was found to be a thiamine auxotroph. The prototrophic strain C. jadinii CBS 5947 was grown on an inorganic salts medium in fed-batch cultures (10-L scale) fed with pure ethanol. Biomass concentrations in these cultures increased up to 100 gbiomass (kgbroth)−1, with a biomass yield of 0.65 gbiomass (gethanol)−1. Model-based simulation, based on quantitative parameters determined in chemostat cultures, adequately predicted biomass production. A different protein content of chemostat- and fed-batch-grown biomass (54 and 42%, respectively) may reflect the more dynamic conditions in fed-batch cultures.ConclusionsAnalysis of ethanol-grown batch, chemostat and fed-batch cultures provided a quantitative physiology baseline for fundamental and applied research on C. jadinii. Its high maximum growth rate, high energetic efficiency of ethanol dissimilation, simple nutritional requirements and high protein content, make C. jadinii a highly interesting platform for production of SCP and other products from ethanol.

Ligand‐Tuning Metallic Sites in Molecular Complexes for Efficient Water Oxidation

AbstractMetal‐organic hybrid catalysts with highly tunable single‐sites are promising for oxygen‐evolution reaction (OER), but molecular‐scale understanding of underlying reaction mechanisms still remain elusive on these bulk materials. Herein, we report a direct construction of heterogenized molecular complexes stabilized on carbon substrates via coordinating Fe−Ni sites with four aromatic carboxylate ligands (FeNi‐Lx). The ligands‐tuning π‐π stacking interaction between aromatic carboxylate ligands and carbon supports promote the oxidative charge accumulation on Fe−Ni sites via fast electron transferring, thus the optimized FeNi‐Lx rendering a mass activity of 6680 A gFe/Ni−1 at 0.3 V overpotential. In situ characteristics and theoretical analysis demonstrate that the OH− nucleophilic attack on hypervalent iron sites induce the reconstruction of active Fe−O−Ni species, accompanying with fast valence increasing. Whereas, during OER, the unexpected valence reduction of Fe−O−Ni sites would be attributed to the oxygen‐generating from OOH* intermediates. These findings would establish an essential understanding of the origin of active centers in molecular complexes catalysts for oxygen‐evolution.