Activation Energy Of Decomposition Research Articles

Stability and hazard properties of improvised nitrocellulose

ABSTRACT Nitrocellulose is a vulnerable and sensitive energetic material that can easily be manufactured from ordinary household chemicals and used for illicit purposes. Hazards of this material can lead to incidents resulting from unplanned initiation in manufacturing, storage or handling.Thermal stability and hazard data for so-called improvised nitrocellulose (IN) are crucial to formulate guidance for storage and handling of such materials recovered from illegal possession. This study focused on the energy content, stability and safety properties of IN. The energy contents increase linearly with nitrogen contents of IN. Improvised nitrocellulose showed a similar sensitivity to impact and electrostatic discharge, but vacuum stability testing demonstrated more gas release (2.8–3.4 cm3 g−1) compared to commercial NC (1.7 cm3 g−1). Chemiluminescence analysis established activation energies for hydrolytic and thermolytic decomposition to be 36 and ~93 kJ mol-1, respectively. Results suggest that NC samples recovered from improvised devices or illegal possession should be handled with special care.

3D printed peripheral vascular stents based on degradable poly(trimethylene carbonate‐b‐(L‐lactide‐ran‐glycolide)) terpolymer

AbstractPoly(L‐lactic acid) (PLLA) is a biocompatible material and has found its application in bioresorbable vascular stents (BVS). However, the crystallization of pure PLLA makes it brittle as a medical implant device. In this work, the biodegradable poly(1,3‐trimethylene carbonate‐b‐(L‐lactide‐ran‐glycolide acid)) (PTLG) terpolymers with improved mechanical performance were developed and processed into peripheral vascular stents by a novel 3D 4‐axial printing technology. The PTLG terpolymers were successfully synthesized by ring‐opening copolymerization of L‐lactic acid (LLA), 1,3‐trimethylene carbonate (PTMC) and glycolide acid (GA) units. The crystallinity and mechanical properties of the PTLG terpolymers with various degradation rate depends on the chain sequence structure and the component contents. Compared with the stent prepared by laser engraving, the peripheral vascular stent prepared by the 3D 4‐axial printing technology exhibit a finer structure and smoother strut surface. It was found that both the strut diameters and the molecular weight of PTMC affect the radial force of the stents and that the apparent activation energy of thermal decomposition of the stents is mainly influenced by the molecular weight of PTMC and the component ratio. Therefore, the addition of the PTMC segment can effectively improve the flexibility of the PTLG terpolymer stent and the 3D printed PTLG terpolymer‐based stent. Furthermore, CCK‐8 and live/dead staining suggested that the stents have good biocompatibility.

Understanding the mechanism of the sulfur mustard hydrolysis reaction on the atomistic level from experiment and first-principles simulations

After World War II, the Baltic Sea was contaminated by dumping unused sulfur mustard (SM) and other chemical warfare agents (CWAs), which now constitutes a huge environmental hazard. We use both experimental and theoretical methods to understand the reactivity of SM in water, in particular the hydrolysis, which is one of the chemical reactions leading to the neutralization of SM. Real conditions present in the Baltic Sea are represented by performing Car-Parrinello molecular dynamics simulations for sulfur mustard in explicit water solution at finite temperature. We study the relative occurrence and stability of various SM conformers in water and analyze the solute–solvent interactions, with special focus on the formation of intra- and intermolecular hydrogen bonds and their lifetime. A missing piece toward the understanding of the sulfonium cation formation and SM hydrolysis reaction is provided by obtaining the activation energy for SM decomposition in water solution from gas chromatography–mass spectrometry (GC-MS) experiments. The complex mechanism of SM hydrolysis is also studied by umbrella sampling simulations to obtain the free energy barrier for the sulfonium cation formation and to provide an atomistic view of the reaction process.

Heterogeneous activation of peroxymonosulfate by sulfur-doped FexMn3-xO4 (x = 1, 2) for trichloroethylene degradation: Non-radical and radical mechanisms

The sulfurized spinels (S-FexMn3-xO4 (x = 1, 2)) were synthesized with the aim to enhance the internal electron transfer process (ETP) when used as a heterogeneous catalyst. A peroxymonosulfate (PMS) based heterogeneous catalytic oxidation (HCO) system was constructed based on the sulfurized spinels with dithionite (DNT) as a reductant to accelerate the redox cycle of surface metal, and trichloroethylene (TCE) was chosen as the target pollutant. The synthesized S-FexMn3-xO4 featured with faster electron transfer and shorter ion transport path compared with the original spinel, especially S-Fe2MnO4 with cubic spinel structure, the activation energy for PMS decomposition significantly decreased via the mediated electron transfer from Fe-S and Mn-S bonds to PMS molecules. In addition, the formation of peroxo species bonding to the surface metal sites (metal-PMS*) was also involved in the formation of high-valent metal species (HVMS) in S-Fe2MnO4/PMS/DNT system, which could directly decompose organics in a non-radical manner via direct electron transfer due to their high redox potentials. Both the radical and non-radical mechanisms contributed to the degradation of TCE, and the contribution of different species followed the order of 1O2 (30.4 %) > metal-PMS* (26.1) > O2•− (21.3) > HVMS (8.0 %) > •HO (7.9 %) > SO4•− (6.3 %). This study dedicates to deepening the understanding of ETP in PMS-HOC system that was based on the spinel catalyst, and provided a new strategy for the synthesis of spinel catalysts.

New Hybrid PVC/PVP Polymer Blend Modified with Er2O3 Nanoparticles for Optoelectronic Applications.

Polymer blend hybrid nanocomposites are of great importance for future optoelectronic applications. This paper presents the preparation of new polymer blend hybrid nanocomposites based on PVC/PVP modified with Er2O3 nanoparticles. A low-cost solution casting method has been used to prepare the polymer nanocomposites at 0.0, 0.1, 0.3 and 0.6 wt% of Er2O3. X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman spectroscopy, and environmental scanning electron microscopy (ESEM) measurements have all been used to examine the impact of a varying wt% of Er2O3 on the structural and optical characteristics of PVP/PVC polymer blends. The PVC/PVP polymer blend and Er2O3 nanoparticles showed a strong interaction, which was validated by XRD, FTIR, and Raman spectrum investigations. The SEM micrographs showed a remarkable complexation among the components of the polymer nanocomposites. The activation energies for thermal decomposition of PVC/PVP doped with different Er2O3 concentrations were less than that of the pure polymer film. The linear and nonlinear refractive indexes, dispersion energy, optical susceptibility and the energy gap values were found to be Er2O3 concentration-dependent. With an increase in Er2O3 concentration to 0.1 and 0.3 wt%, the dispersion energy and nonlinear refractive index improved, and thereafter decreased when the concentration was further increased to 0.6For the film doped with 0.1 wt% Er2O3, the optical band gap (Eopt) of the composite film enhanced by about 13%. The optical absorption measurements revealed clear improvements with the addition of erbium oxide. Higher refractive index values of PVC/PVP/Er2O3 films qualify the polymer blend as a cladding for electro-optic modulators. Our results indicated that the PVC/PVP/Er2O3 polymer films could be suitable for optoelectronic space applications.

Graphene Oxide-Intercalated Tetrazole-Based Coordination Polymers: Thermally Stable Hybrid Energetic Crystals with Enhanced Photosensitivity

High-energy-density photosensitive pyrotechnics with good thermal stability have been in increasing demand in recent years. In this paper, graphene oxide (GO)-intercalated energetic coordination polymers (ECPs) are prepared with improved thermostability but great photosensitivity by using high nitrogen compounds azotetrazole (AT) and 5,5'-bistetrazole-1,1'-diolate dehydrate (BTO) as ligands. The decomposition activation energy (Ea) of Cu-AT has been increased from 135.7 to 151.9 kJ·mol-1 after intercalating 5 wt% GO, and in the meantime, the exothermic peak temperature (Tp) was increased by 12.6 °C. However, the decomposition Ea of Cu-BTO decreased under the effect of the same amount of GO with little effect on Tp. This confirms that GO has stabilization effects on the Cu-AT crystal, whereas the catalytic effects on Cu-BTO would dominate after dehydration with its crystal lattice collapse. Also, when the content of GO was 3%, the resultant GO0.03-Cu-AT exhibits a higher density (2.88 g·cm-3) and good thermostability (Tp = 293.7 °C). This ECP shows excellent low-energy laser ignition performance, which can be ignited with an energy of less than 1 mJ at a wavelength of 976 nm. Low-energy laser initiation is considered to be a safer but more reliable method than the traditional electrical-based ones.

Effects of urea on the thermal decomposition behavior of ammonium nitrate: A reliable thermal safety performance enhancer

To address the actual disaster of thermal decomposition and explosion of ammonium nitrate (AN), a commonly used raw material, urea was selected as an additive to study its effect on the thermal decomposition of AN through experimental and theoretical methods. The thermal decomposition kinetics, energy release, self-reaction properties of adiabatic environments, and escaping gaseous products have all been discussed. It was found that urea has an inhibitory effect on the crystalline transformation of AN stored at room temperature, which is beneficial to its thermal safety. The results showed that urea increased the activation energy of the thermal decomposition of AN, raised the temperature of the initial reaction and reduced heat generation. Furthermore, the action mechanism of urea is suggested to be heat absorption by its thermal decomposition and the escape of ammonia. Finally, the study carried out an engineering assessment of the thermal safety of AN under the action of urea and found that the addition of urea greatly enhanced the thermal safety performance of stored and transported AN. The comprehensive analysis concluded that a small dose of urea could be added to enhance the thermal stability of AN without affecting its normal function.

Combustion simulations of AlH3 and ethanol nanofluid by ReaxFF

To alleviate the growing energy crisis, ethanol has been developed and applied gradually as an ideal biofuel to replace gasoline. The AlH3 nanoparticle is an excellent fuel additive with broad applications. In this work, the ReaxFF-lg reactive dynamics simulations were proceeded to explore the detailed mechanisms of AlH3 and ethanol nanofluid fuel. At varying temperatures, AlH3 exhibits different morphologies: branch-like expansion at the lower temperatures; micro-explosion and reaggregation into larger clusters at high temperatures. Overall, AlH3 accelerates the decomposition of ethanol and shortens the ignition delay. AlH3 also reduces the activation energy for ethanol decomposition from 79.09 to 69.05 kJ/mol. The conversion of coordination number for Al-O bonds indicates that Al2O3 is the final product of Al element. The simulation results reveal a new mechanism: AlH3 promotes the dissociation of H in the hydroxyl, making the initial decomposition of ethanol to C2H5O (CH3CH2O, CH3CHOH and CH2CH2OH) selective. The released H forms more OH and HO2 radicals to promote the conversion of intermediates to stable products. The Al2O3 oxide layer delays the ethanol combustion kinetics as well. This study provides an atomic perspective on the combustion mechanisms of AlH3 and ethanol nanofluid fuel and is expected to guide the development and application of AlH3-based fuels.

Facile preparation of Fe/N-based biomass porous carbon composite towards enhancing the thermal decomposition of DAP-4

Fe/N-based biomass porous carbon composite (Fe/N-pCarbon) was prepared by a facile high-temperature carbonization method from biomass, and the effect of Fe/N-pCarbon on the thermal decomposition of energetic molecular perovskite-based material DAP-4 was studied. Biomass porous carbonaceous materials was considered as the micro/nano support layers for in situ deposition of Fe/N precursors. Fe/N-pCarbon was prepared simply by the high-temperature carbonization method. It was found that it showed the inherent catalysis properties for thermal decomposition of DAP-4. The heat release of DAP-4/Fe/N-pCarbon by DSC curves tested had increased slightly, compared from DAP-4/Fe/N-pCarbon-0. The decomposition temperature peak of DAP-4 at the presence of Fe/N-pCarbon had reduced by 79°C from 384.4°C (pure DAP-4) to 305.4°C (DAP-4/Fe/N-pCarbon-3). The apparent activation energy of DAP-4 thermal decomposition also had decreased by 29.1 J/mol. The possible catalytic decomposition mechanism of DAP-4 with Fe/N-pCarbon was proposed.

Oxide desorption process from InSb surface under Sb flux

In this work, the process of oxide removal from the InSb (001) surface was studied in situ by high-energy electron diffraction in vacuum and under an antimony flux. The dependence of the oxide thickness on the annealing temperature was obtained. It has been found that the antimony flux slows down the process of oxide removal due to the oxide formation reaction. The oxide removal process was described by a system of kinetic equations, the activation energy of oxide decomposition was determined Keywords: InSb, oxide, activation energy, desorption.

INFLUENCE OF THE PHASE TRANSFER CATALYST ON THE ACCUMULATION AND DECOMPOSITION OF ETHYLBENZENEHYDROPEROXIDE

The regularities of ethylbenzene oxidation and hydroperoxide decomposition in microheterogeneous systems formed by adding sodium dodecyl sulphate to hydrocarbon media have been studied. A pronounced influence of surfactant nature on the transformation mechanism has been revealed. Anionic micellar surfactants including a linear hydrocarbon fragment catalytically accelerate ROOH decomposition, whereas hydrocarbon soluble non-ionic surfactants and solid oxides practically do not influence the reaction rate. Detailed study of the degradation kinetics in the presence of anionic alkyl sulphates has shown that the accelerating effect of surfactants is connected with their colloidal properties, namely, with the formation of joint aggregates of inverse micelles type, which facilitate the destruction of the peroxide bond. For the first time, a synergistic inhibitory effect of sodium alkyl sulphate mixtures with phenolic antioxidants in the oxidation of various hydrocarbons has been found. During the oxidation of ethylbenzene with minor additives (<1%) of sodium dodecyl sulphate (DDS) a unique case of effective self-inhibition has been determined, the mechanism of which includes two steps. Hydroperoxide, the main source of free radicals, decomposes heterolytically in joint microaggregates with DDS. The decomposition occurs selectively with the formation of acetaldehyde and phenol. Phenol being an acceptor of free radicals inhibits the oxidation of ethyl benzene. The main oxidation product of RH in this system is phenol and acetaldehyde. It should be noted that phenols formation at decomposition of alkylaromatic ROOH is usually connected with strong acids. In the case of DDS decomposition of ROOH seems to be driven by the successful orientation of ROOH molecules in the microaggregates formed by anionic surfactants. But a number of experimental factors, namely the influence of the carbon chain length in sodium alkyl sulphates on the dodecane oxidation rate and inertness of the Na2SO4 dispersion in the hydroperoxide decomposition reactions, make it possible to suggest the catalytic reaction of ROOH. Suggest that the catalytic effect of DDS on hydroperoxide decomposition is connected with its colloidal properties and decomposition occurs in common microaggregates formed by DDS and ROOH. The effective activation energy of ROOH decomposition at concentration of 10 mm is Eef = 66.3 kJ/mol. The oxidation of ethyl benzene is completely inhibited at low additions of DDS (1 mM), and the decomposition rate in an atmosphere of N2 significantly increases. DDS increases the effective decomposition constant of ROOH. This surfactant can be considered as an effective catalyst of ROOH decomposition. For citation: Kashkay A.M. Influence of the phase transfer catalyst on the accumulation and decomposition of ethylbenzenehydroperoxide. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 2. P. 100-106. DOI: 10.6060/ivkkt.20236602.6684.

Процесс десорбции оксида с поверхности InSb в потоке сурьмы

In this work, the process of oxide removal from the InSb (001) surface was studied in-situ by high-energy electron diffraction in vacuum and under an antimony flux. The dependence of the oxide thickness on the annealing temperature was obtained. It has been found that the antimony flux slows down the process of oxide removal due to the oxide formation reaction. The oxide removal process was described by a system of kinetic equations, the activation energy of oxide decomposition was determined.

INFLUENCE OF BURNING RATE INHIBITORS ON THE THERMAL BEHAVIOR AND DECOMPOSITION KINETICS OF AMMONIUM PERCHLORATE

The addition of burning rate inhibitors (BRIs) to propellant formulations can be effective in reducing the burning rate of composite solid propellants (CSPs). Ammonium perchlorate (AP) is commonly used as an oxidizer for CSPs and is a major component of propellants. Therefore, it is of great significance to study the thermolysis performance of AP in the presence of BRIs. In this work, differential scanning calorimetry and thermogravimetric analysis were utilized to study the thermolysis of AP. Oxamide (OXA), ammonium sulfate (AS), ammonium oxalate (AO), and carbamide (CA) were selected as the BRIs. The results showed that as the BRI content increased, the endothermic peak remained essentially unchanged. The exothermic peak in the low-temperature decomposition (LTD) stage shifted to a hightemperature field, while the exothermic peak in the high-temperature decomposition (HTD) stage shifted to a low-temperature field. Furthermore, associated kinetic studies showed that the decomposition activation energies of AP with inhibitors during the LTD stage were higher than that of pure AP, proving that the selected BRIs could effectively inhibit the thermolysis of AP. However, during the HTD stage, the values of the activation energies for decomposition gradually increased in the order of AP + AO, AP + OXA, AP + CA, AP, and AP + AS, indicating that only AS had the effect of inhibition at this time.

Isothermal structural evolution of CL-20/HMX cocrystals under slow roasting at 190 °C.

As a new type of energetic material, cocrystal explosives demonstrate many excellent properties, such as high energy density and low sensitivity, due to the interaction between the molecules of the two components. The known decomposition temperature is 235 °C for CL-20/HMX cocrystals at a faster heating rate. CL-20 molecules could separate from the cocrystal matrix and decompose at a higher temperature, much lower than the decomposition temperature. The current work provided deep insight into the isothermal structural evolution of CL-20/HMX cocrystals with slow roasting at 190 °C. We found that the initial decomposition originates from separating CL-20 molecules from the surface along the (010) plane of the cocrystals. The gas products, such as NO2 and NO, escape from the largest exposed surface of the (010) plane and generates microbubbles and microholes. At the same time, the residual HMX molecules form δ-phase HMX crystals and shrink the volume by 72%. By increasing the time held at 190 °C, the decomposition of CL-20 molecules and recrystallization of the residual HMX molecules form a gully-like structure on the (010) plane of the CL-20/HMX cocrystal. After a long time at 190 °C, the CL-20 component completely decomposes, and all HMX molecules recrystallize in the δ-HMX form. The interaction between HMX and CL-20 molecules makes the decomposition rate of the CL-20/HMX cocrystal much slower than that of the CL-20 pure crystal with a similar decomposition activation energy during isothermal heating. This work can help to deeply understand the safety of CL-20/HMX cocrystal explosives at a temperature lower than the recognized decomposition temperature.

Improvement of the Thermal Stability of Polymer Bioblends by Means of Reactive Extrusion

Poly(lactic acid) (PLA) and biosourced polyamide (PA) bioblends, with a variable PA weight content of 10-50%, were manufactured by melt blending in order to improve the behavior of PLA against thermal degradation. The effect of reactive extrusion on the thermal performance of PLA within bioblends was analyzed. The reactive extrusion was made by means of the addition of a styrene-acrylic multi-functional-epoxide oligomeric reactive agent (SAmfE), with the commercial name of Joncryl. Four parameters were considered in order to study the thermal behavior of bioblends against thermal decomposition: the onset decomposition temperature, the shape and temperature interval of the thermal decomposition patterns, the activation energy of the thermal decomposition, and the evidence leading to the most probable mechanism. The latter was determined by means of three evidence: standardized conversion functions, y(α) master plots, and integral mean error. It was shown that reactive extrusion of PLA as well as PA incorporation to the polymer matrix of PLA were responsible for an increase in the onset decomposition temperature of 10.4 °C. The general analytical equation (GAE) was used to evaluate the kinetic parameters of the thermal degradation of PLA within bioblends for various reaction mechanisms. It was shown that the random scission of macromolecular chains is the best mechanism for both untreated and treated PLA by means of reactive extrusion. It was shown that reactive extrusion together with higher content of PA resulted in an increased protective effect against the thermal degradation of PLA as demonstrated by an increase in activation energy of 60 kJ/mol. It was found that there is a relationship between the increase in activation energy and the increase in the onset decomposition temperature when using reactive extrusion. The improvement of the thermal stability of bioblends by means of reactive extrusion was explained by an increase in the complex viscosity from 980 to 2000 Pa·s at 0.06 rad/s and from 250 to 300 Pa·s at 630 rad/s for bioblend containing 30% of PLAREX and by a finer dispersion of PA within the PLAREX matrix. Results from DSC were not conclusive regarding the compatibility between both phases.

Исследование двойного электрического слоя на композиционных материалах «карбид тугоплавкого металла — углеродное волокно» в пероксиде водорода и сульфате натрия

The electric double layer was studied by impedance spectroscopy on the surface of various composite materials: molybdenum, tantalum and niobium carbides in 1 M sodium sulfate solution and concentrated hydrogen peroxide solution. The data on the activation energy of the electrocatalytic decomposition of hydrogen peroxide on the surface of composite materials were compared with the capacity of the electrical double layer in hydrogen peroxide solution.

Interface engineering of Fe3Se4/FeSe heterostructures encapsulated in MXene for boosting LiPS conversion and inhibiting shuttle effect

Developing advanced catalysts with high chemisorption toward promoting the conversion of lithium polysulfide (LiPS) is the key to the commercial application of Lithium-sulfur (Li-S) batteries. Here, a novel catalyst consisting of Fe3Se4/FeSe heterojunctions encapsulated in two-dimensional (2D) MXene nanosheets is prepared by in situ growth and selenization of Fe-MOFs. The MXene skeleton captures polysulfides effectively and the Fe3Se4/FeSe heterojunction plays a catalytic role as well as their strong synergistic effect achieves “capture-adsorption-catalysis” of LiPS. A Li-S battery with Fe3Se4/FeSe@MXene-PP separator delivers a high specific capacity (1104.2 mAh/g at 0.2C) and outstanding rate capacity (758.8 mA h g−1 at 4C). Even with sulfur loading as high as 5.8 mg cm−2, the Li-S battery has a high specific capacity of 862.6 mAh/g at 0.2C and cycle stability (92.3 % retention after 120 cycles). The involved mechanisms of performance improvement were discussed and demonstrated by density function theory (DFT) calculations and in situ Raman analysis. Interface engineering of the Fe3Se4/FeSe increases the density of states at the Fermi level, reduces the activation energy of Li2S decomposition, and the establishment of an internal electric field accelerates charge transfer. This work provides an effective approach to the design of high-performance catalysts for improved Li-S batteries.

Applying the Inelastic Thermal Spike Model to the Investigation of Damage Induced by High‐Energy Ions in Polymers

AbstractThis work reports on damage production in polymers by high‐energy ions within the framework of the inelastic thermal spike model (i‐TS). The model is used to describe the effective size of the damaged region around the ion path (the track size) in amorphous poly(methyl methacrylate) (PMMA) and the semicrystalline poly(p‐phenylene sulphide) (PPS), poly(ethylene terephthalate) (PET), and poly(vinylidene difluoride) (PVDF). Track size calculations are compared to experimental data deduced from measurements of crater size, bond‐breaking cross‐sections, changes in crystallinity and electron density, track etching, and electrical depolarization. The use of data obtained from distinct types of damage provides a broad platform to test the applicability of the model to polymers. This work shows that the i‐TS correctly describes the dependence of the track size on energy loss obtained from most experimental probes, when the activation energy of thermal decomposition of the polymers is used as the criterion of track formation, using an electron–phonon mean free path of ≈3 nm. As damage is not uniform across the ion track radial dimension, there are fine variations in the experimental damage radii that can only be accounted for by using multiple activation processes. Amorphization radii of the semicrystalline polymers are not directly correlated to melting induced by the ions.

Catalytic effect investigation of α-Fe2O3 and α-Fe2O3-CMS nanocomposites on the thermal behavior of NC/DEGDN mixture: DSC measurements and kinetic modeling

In this work, the thermal behavior and kinetics of energetic systems containing α-Fe2O3 and iron oxide–carbon mesospheres (α-Fe2O3-CMS) with nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN)-based composites have been investigated using differential scanning calorimetry DSC and four isoconversional kinetic methods, respectively. The obtained results indicate that NC/DEGDN show only one decomposition peak, corresponding to the decomposition of the nitrate esters. Furthermore, the introduction of α-Fe2O3 and α-Fe2O3-CMS have lowered the peak temperature by 3.1 °C and 4.7 °C, respectively. Besides, the activation energy of the thermal decomposition of NC/DEGDN was decreased by 11.9 kJ/mol and 27.97 kJ/mol, after the introduction of α-Fe2O3 NPs and α-Fe2O3 NPs supported on CMS. These results confirm the good catalytic effect of the added catalysts on the thermal decomposition of the NC/DEGDN mixtures. However, the best catalytic effect was provided by the α-Fe2O3-CMS. Furthermore, the three considered systems were found to decompose according to different integral models g(α).

Bioenergetic control of soil carbon dynamics across depth

Soil carbon dynamics is strongly controlled by depth globally, with increasingly slow dynamics found at depth. The mechanistic basis remains however controversial, limiting our ability to predict carbon cycle-climate feedbacks. Here we combine radiocarbon and thermal analyses with long-term incubations in absence/presence of continuously 13C/14C-labelled plants to show that bioenergetic constraints of decomposers consistently drive the depth-dependency of soil carbon dynamics over a range of mineral reactivity contexts. The slow dynamics of subsoil carbon is tightly related to both its low energy density and high activation energy of decomposition, leading to an unfavourable ‘return-on-energy-investment’ for decomposers. We also observe strong acceleration of millennia-old subsoil carbon decomposition induced by roots (‘rhizosphere priming’), showing that sufficient supply of energy by roots is able to alleviate the strong energy limitation of decomposition. These findings demonstrate that subsoil carbon persistence results from its poor energy quality together with the lack of energy supply by roots due to their low density at depth.