Efficient and low-cost electrocatalysts are crucial for sustainable hydrogen production via water splitting. Here, 33 single-atom catalysts (SACs) supported on C24N24 were systematically investigated using first-principles calculations. Structural, thermal, and electrochemical stability analyses indicate that only In-, Si-, Ge-, and Bi-C24N24 are stable under operating conditions. Hydrogen adsorption free energy calculations reveal that Ge-C24N24 exhibits the most optimal Delta G(H*) for acidic HER (-0.14 eV), followed by In-C24N24 (-0.38 eV). In alkaline media, Ge-C24N24 also shows the most favorable thermodynamic profile (0.21 eV). However, explicit kinetic analysis of the water dissociation step demonstrates high activation barriers (>1.83 eV) for all candidates, indicating sluggish alkaline HER kinetics. Machine-learning analysis based on the SISSO algorithm identifies metal charge, electronegativity, metal-nitrogen distance, valence electron count, electron affinity, and first ionization energy as key descriptors governing HER activity trends. Overall, Ge-C24N24 emerges as a promising SAC for acidic HER, while the large water dissociation barriers highlight the intrinsic kinetic limitations of C24N24-supported SACs for alkaline HER. These findings provide mechanistic insights and theoretical guidance for rational catalyst design.

Serving as a highly eco-compatible oxidizing substance, hydrogen peroxide (H2O2) finds extensive utility chemical production, environmental remediation, and renewable energy systems. Employing the electrocatalytic two-electron oxygen reduction pathway (2e-ORR) offers a practical route for on-site and green synthesis of H2O2; however, the design and fabrication of electrocatalysts with high selectivity and activity remain a major challenge owing to the competing four-electron ORR pathway. In this article, we employed the first-principles calculations based density functional theory (DFT) to systematically investigate metal single-atom catalysts(SACs) supported on Sc2CS2 MXene for electrochemical H2O2 production via the 2e-ORR. A total of 42 metal elements were evaluated based on four key criteria: structural robustness, electrochemical stability, intrinsic catalytic activity, and reaction pathway selectivity. The computational results demonstrate that several candidate systems, including Ca-, Cd-, Cu-, Pd-, Sr-, Zn-, Ba-, Sb-, and Ag-decorated Sc2CS2, exhibit a thermodynamic tendency ward the 2e-ORR pathway over the competing four-electron route. Among all screened catalysts, Pd-Sc2CS2 shows the most outstanding catalytic performance, delivering an ultralow overpotential(eta) of only 0.05 V in both acidic and alkaline media. Further electronic structure analyses reveal that this remarkable activity originates from effective orbital hybridization and charge redistribution at the interface. Specifically, strong interactions occur between the Pd d orbitals and the O p orbitals of adsorbed intermediates. This synergistic electronic effect enables O-O bond activation moderately while suppressing its undesired dissociation. In addition, machine learning analysis grounded in the SISSO algorithm reveals the key descriptors dictating catalytic performance, including valence electron count, first ionization energy, electronegativity, metal-S bond length, electron finity, and metal atomic charge. These findings provide fundamental exploration of the selectivity and activity MXene-supported SACs and offer reliable theoretical guidance for the strategic design of high-performance electrocatalysts for H2O2production.

Magnesia-calcia(MgO-CaO) refractories are widely used in tundish linings and continuous casting furnaces owing to their high melting point, thermal stability, resistance to slag corrosion, and effectiveness in purifying molten steel. However, their susceptibility to hydration in humid environments severely limits their practical applications. To enhance the hydration resistance of MgO-CaO materials, this study presents a novel one-step catalytic chemical vapor deposition method using soybean oil as a carbon source and cobalt(Co) as a catalyst to synthesize carbon nanotubes(CNTs) and calcium carbonate(CaCO3 ) co-coated superhydrophobic MgO-CaO grains. The effects of pyrolysis temperature, holding time and catalyst loading on the microstructure and hydration resistance of the modified MgO-CaO grains were systematically investigated. The results indicate that the optimal synthesis conditions for the CNTs-CaCO3 co-coated superhydrophobic MgO-CaO grains are as follows: reaction temperature of 700 degrees C , 2.0% (mass ratio of the supported catalyst to MgO-CaO grains) Co catalyst loading, and holding time of 1 h. Under these conditions, the modified aggregates exhibited a water contact angle of 155 degrees, and a minimal hydration-induced weight

Hydrogen peroxide (H2O2) is a versatile chemical widely used in electronics, medical disinfection, and wastewater treatment. In this work, density functional theory (DFT) calculations were employed to systematically explore the catalytic potential of single transition-metal atoms supported on Mo2CO2 MXene (TM-Mo2CO2) for electrochemical H2O2 production via the two-electron oxygen reduction reaction (2e- ORR) pathway. The results indicate that several transition metals (Ag, Au, Cd, Cu, Fe, Pd, Ti, and Zn) exhibit excellent structural and electrochemical stability on the Mo2CO2 surface. Among these, Ag-Mo2CO2, Cu-Mo2CO2, and Pd-Mo2CO2 preferentially catalyze the 2e- ORR pathway, with Ag-Mo2CO2 showing the most favorable performance-achieving a remarkably low overpotential (eta) (0.08 V at both pH = 0 and 13) and a minimal energy barrier (0.17 eV)- significantly outperforming pristine Mo2CO2 in both activity and selectivity toward H2O2 formation. These findings demonstrate the feasibility of MXene-based single-atom catalysts (SACs) for efficient electrochemical H2O2 production and provide theoretical insights to guide the rational design of efficient MXene-supported 2eORR catalysts

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) based on SnO2 electron transport layer (ETL) has exceeded 26.1 %. However, defects located at interfaces of ETL/perovskite films and perovskite/hole transport layer (HTL) remain a key factor in reducing performance of PSCs, especially in the air environment. The effect of single defect passivation of SnO2 ETL/perovskite or perovskite films/HTL on performance of PSCs is limited. In addition, the green and stable characteristics of passivation agents are important factors that must be considered for the sustainable development of perovskite solar cells. To address this, natural amphiphilic betaine molecules and green hydrogen bond system composed of imidazole and salicylic acid (ImA-SA HBS) are introduced, which simultaneously passivate SnO2 ETL/perovskite and perovskite/HTL defects. The addition of betaine not only improves the charge extraction at the SnO2/perovskite interface, but also suppresses the recombination of photogenerated carriers. Furthermore, due to introduction of ImA-SA HBS, the charge transport between perovskite grains and energy level matching of perovskite/HTL interface are improved, which increase the PCE of PSCs prepared in air from 20.67 % to 22.20 %. Furthermore, the PSCs passivated with betaine and HBS show no decrease in PCE after being stored in air for 66 days. This paper provides theoretical basis and technical support for defect passivation strategy and performance optimization of PSCs prepared in air environment.

MgO-CaO refractories are widely used in steelmaking, cement production, and non-ferrous smelting owing to their high refractoriness, thermal stability and slag resistance. However, the strong tendency of CaO to hydrate leads to volume expansion, cracking, and structural degradation in refractories, severely limiting the stability and applicability of MgO-CaO refractories and CaO-based materials under practical conditions and has thus become a "century-old challenge." In this study, a one-pot catalytic pyrolysis route was developed to construct dual C/CNTCaCO3 coating on sintered doloma grains (CCSDGs) using waste oil as starting material. The effects of pyrolysis temperature, Fe-Ni mole ratio, types of waste oil and catalyst loading on coating formation and hydration resistance of the coated doloma grains were systematically investigated. Under optimized processing conditions (700 degrees C, 2 wt% Fe-Ni catalyst at a mole ratio of 8:2, waste soybean oil), a dense C/CNT layer and a continuous CaCO3 shell were formed on the surface of the sintered doloma grains, this dual protective layer effectively inhibited water penetration into the as-prepared CCSDGs, resulting in a 10.9-fold reduction in hydration weight (70 degrees C/85% RH/24 h) gain compared with uncoated doloma grains. These findings highlight a simple, efficient, and low-cost strategy for fabricating durable doloma-based refractories with significantly enhanced hydration resistance and the high-value-added utilisation of waste oil, offering promising potential for their large-scale industrial applications.

Two-dimensional (2D) MXenes possess great potential for lithium-ion batteries (LIBs) owing to its excellent physical and chemical properties. However, the re-stacking issue of MXene nanosheets negatively affects their large-scale application. Herein, the sulfur-doped Ti3C2Tx/bacterial cellulose-derived carbon nanofibers (S-Ti3C2Tx/BCCNFs) composite was prepared via a hydrogen bonding assembly combined with an annealing-assisted melt-diffusion strategy. This elaborately designed 2D/1D architecture not only significantly alleviates the re-stacking of MXene nanosheets and improves the specific surface area and pore structure, but also enriches the MXene surface with O and S functional groups. Density functional theory (DFT) calculations reveal that both Ti3C2S2 and Ti3C2O2 MXene present higher Li+ adsorption ability and lower diffusion barrier than Ti3C2F2 MXene. Owing to the synergistic optimization of morphology structure and surface functional groups, the S-Ti3C2Tx/BCCNFs anode possesses a high surface capacitive contribution and rapid Li+ diffusion kinetics. As the anode for LIBs, the S-Ti3C2Tx/BCCNFs composite exhibits specific capacities of 687.9 mAh g−1 after 200 cycles at 0.5 A g−1 and 588.2 mAh g−1 after 300 cycles at 1.0 A g−1.

SiCw self-strengthened porous ceramics were fabricated utilizing SiC powder as the raw materials, Si powder and carbon black as the precursor materials for the self-bonding SiC phase, 2 wt% AlF3 & sdot;3 H2O as the additive agent, and 1.0 vol% triethanolamine dodecyl sulphate as foaming agent. The effects of self-bonding SiC content on the phase constituents, microstructural morphologies, and mechanical strength of SiCw self-strengthened porous ceramics specimens were investigated. As the self-bonding SiC content rose from 0 wt% to 30 wt%, the linear shrinkage, bulk density and mechanical strength of the as-fabricated porous specimens increased, while the porosity correspondingly decreased. The incorporation of an appropriate amount of self-bonding SiC led to a reduction in the average quasi-spherical pore diameter within the porous specimens and enhanced their mechanical strength. At a self-bonding SiC content of 30 wt%, a large number of SiCw with a mean diameter of 58 nm and a length of about several microns were generated via a gas-solid reaction mechanism in SiCw selfstrengthened porous specimens. The flexural and compressive strengths of SiCw self-strengthened porous specimens with a porosity of 76.9% were respectively 2.6 MPa and 3.7 MPa, which were significantly superior to the corresponding values (1.1 MPa and 1.5 MPa) of the porous ceramics without self-bonding SiC. Additionally, their linear shrinkage was merely 3.1%.

The aging or failure of power transformers poses a significant threat to both production and daily life, and employing characteristic dissolved gas detection offers an effective early warning system to mitigate such risks. In this study, we conducted first-principles simulations to investigate the adsorption and sensing characteristics of two-dimensional intrinsic and noble metal-decorated AsP monolayers toward four characteristic gases (C2H4, H2, C2H2, and CO). Additionally, we conducted an in-depth analysis of the electronic structure and its impact on the sensing performance within the adsorption systems. The study demonstrates that the introduction of a noble metal improves gas behaviors, with the Ru-decorated AsP monolayer exhibiting particularly superior adsorption and sensing performances. At different temperatures, the H2/Ru-AsP adsorption system in transformer oil demonstrates excellent adsorption behavior. During the initial and later stages (from 350 to 900 K) of power transformer failure, the adsorption energy change is approximately -0.8 eV, and its desorption time is less than 0.5 s. Even in scenarios involving severe faults that result in equipment overheating and the subsequent generation of gases such as C2H2 and C2H4, the sensor demonstrates a consistent response time of less than 0.3 s. This work provides valuable research support for characteristic gas detection in the safe operation of power transformers.

WO3-based dual-band electrochromic materials have attracted extensive attention due to the ability to selectively control sunlight and solar heat. However, existing materials all have inevitable drawbacks, especially the weak independence of near-infrared (NIR) regulation and high energy consumption. The root cause of these defects lies in the poor understanding of their visible-NIR independent modulation mechanisms. Therefore, for the first time, we specifically elucidate the dynamic dual-band modulation mechanism of monoclinic WO3-x nanowires from the essential perspective of electronic behavior and state changes, and analyze the electrochemical behavior contribution of each stage. The co-controlled modulation of absorption and reflection by multiple mechanisms are the key for achieving selective visible-NIR regulation. The modulation of "slight cool (only NIR-blocked)", "cool (NIR significant shielded with slight damping visible light)" and "dark (both visible-NIR obstructed)" modes are attributed to "the polaron absorption", "LSPR absorption and free-electron reflection" and "LSPR absorption and electronic bandgap transitions". Additionally, the indicators (the most restricted voltage of Li+- ion injection) and improvement measures for enhancing NIR-independent modulation are provided by introducing novel correction and contribution-calculation approaches. Notably, the electrode also exhibits outstanding comprehensive dual-band electrochromic performance. Additionally, an energy consumption of 14.1 mA h/m2 (30 mW h/m2) for completing round-trip switch of "bright-dark" modes, comparable to the lowest energy consumption documented in electrochromic researches. The constructed semi-solid device offers a dynamic temperature control range of 6.6 degrees C, underscoring significant practical application potential.

To inhibit the rapid hydration of calcium oxide (CaO) and expand its applications in metallurgy and construction, calcium carbonate (CaCO3) and carbon nanotubes (CNTs) co-modified superhydrophobic doloma grains (CCSDGs) were one-pot synthesized through a catalytic chemical vapor deposition method. The water contact angle of the as-synthesized CCSDGs was as high as 158.4 degrees. In comparison with CaCO3-coated, CNT-coated, and uncoated doloma grains, the CCSDGs demonstrated a hydration weight gain of only 0.32 wt% under 70 degrees C, 85 % relative humidity over 24 h, which was respectively 80.7-82.5 %, 93-95.3 %, and 95.4 % lower than those of its counterpart samples. When the CCSDGs were soaked in liquid water for 48 h at room temperature, the pH value of the dispersion only increased from 6.02 to 9.01, whereas that for raw doloma grains (DGs), CaCO3-coated DGs and CNTs-coated DGs increased respectively from 6.03 to 12.09, 6.05 to 11.17, and 5.84 to 11.38, demonstrating an excellent liquid water hydration resistance of the co-modified sample. The apparent hydration activation energy of the prepared CCSDGs for water vapor (90 % relative humidity) was found to be 50.89 kJ/mol, which is 1.88 times higher than that of the uncoated sample. Density functional theory calculations revealed that cobalt catalysts not only promoted the formation of CNTs, but also the conversion of CaO to CaCO3. This study provides a novel approach for preparing superhydrophobic doloma grains and offers a long-term storage method for CaOcontaining materials.

In this study, we report a novel one-pot synthesis of superhydrophobic doloma grains (CCSDGs) with dual coatings of carbon nanotubes (CNTs) and calcium carbonate (CaCO3) via a catalytic chemical vapor deposition strategy using soybean oil as a carbon source. The effects of catalyst type (Fe and Ni), reaction temperature, dwelling time, and catalyst loading on the formation and hydration resistance of the prepared CCSDGs were systematically investigated. Ni catalysts demonstrated superior catalytic performance compared to Fe, and the optimal formation conditions for the CNT/CaCO3 dual coating were a pyrolysis temperature of 600 degrees C, a dwelling time of 1h, and a Ni loading of 2 wt%. The resulting CCSDGs displayed a water contact angle of 151 degrees and a hydration weight gain of 1.42 wt%, representing a 4.95-fold reduction compared to the raw doloma grains. The synergistic effect of the hydrophobic CNT layer and the dense protective CaCO3 shell effectively inhibited moisture penetration and hydration reactions of CaO. This work presents a simple strategy for enhancing the hydration resistance and environmental durability of CaO-based materials.

In this study, the mechanical and electronic properties of W2CoB2 hard phases in the WCoB–TiC ceramic composites with varying Cr contents were analyzed using first-principles calculations. Experimental measurement was conducted to determine the microstructure, hardness, transverse rupture strength (TRS), and fracture toughness (KIc) of WCoB–TiC ceramic composites with different Cr contents. First-principles calculations showed that adding a small amount of Cr could increase the bulk elastic modulus of the material. However, as the concentration of Cr increased, its bulk elastic modulus decreased. Moreover, it was found that Cr doping effectively enhanced the material's toughness, which might be attributed to strengthening the covalent bond property of the B–Cr chemical bond with higher Cr doping concentrations. The experimental results indicated that Cr doping reduced the density of Cubatic ceramic composites. Still, a small amount of Cr could refine the grain size of the hard phases, thereby enhancing the overall mechanical properties of the composites. The WCoB–TiC ceramic composites achieved the highest hardness, TRS, and KIc values of 92.3 HRA, 906.5 MPa, and 12.45 MPa ∙ m1/2, respectively, at a Cr content of 2.0 wt.

The methanol oxidation reaction is a critical half-reaction in direct methanol fuel cells (DMFCs), but its efficiency is limited by the low activity and poor stability of traditional electrocatalysts. This study reports the development of a high-performance PtCo/Mo2CTx catalyst for methanol oxidation in DMFCs. Synthesized by depositing PtCo alloy nanoparticles on Mo2CTx sheets prepared via cetyltrimethylammonium bromide-assisted etching of Mo2Ga2C, the PtCo/Mo2CTx catalyst achieved enhanced interlayer spacing and excellent dispersion of active sites. The optimized PtCo/Mo2CTx catalyst exhibited remarkable catalytic activity, reaching a mass activity of 2296 mA·mgPt−1—6.5 times that of commercial Pt/C. Electrochemical studies confirmed the catalyst’s low charge transfer resistance, high electrochemical surface area, and strong CO anti-poisoning ability. Stability tests showed that the catalyst retained 62.26

The rising levels of CO2 have resulted in significant environmental challenges. Among the potential solutions, the electrochemical CO2 reduction reaction (eCO2RR) has emerged as a highly effective approach, offering the dual benefits of reducing carbon emissions and supporting sustainable energy production. Of the various possible products, CH4 is regarded as the most ideal outcome of eCO2RR. Consequently, designing and synthesizing high-performance eCO2RR catalysts for CH4 production is of critical importance. In this study, density functional theory (DFT) calculations are utilized to explore the catalytic performance of ten transition metal atoms anchored on Fe2B2 MBene as single-atom catalysts (SACs) for eCO2RR to CH4. The results reveal that Ti-Fe2B2 SAC exhibits excellent electrocatalytic activity and high catalytic selectivity, with a limiting potential of -0.48 V. Furthermore, the electronic properties of Ti-Fe2B2 SAC are analyzed. This work offers valuable insights into MBene-based electrocatalysts for eCO2RR and provides guidance for designing robust catalysts with enhanced activity and selectivity for eCO2RR.

M3A2X phase is a type of ternary layered MAX-phase-like materials. To date, only four stable M3A2X phases have been discovered. In this research, high-throughput density functional theory calculations were employed to systematically identify stable M3A2X phases and then predict their properties. Starting from 240 possible compositions and 51 structural models for each composition, 12 M3A2X phases successfully passed three rounds of stability assessment (thermodynamic, dynamic, and mechanical stabilities) and thus are stable. Crystal structures of stable Sc3S2C, Y3S2C and Y3Se2C are novel and different from those of synthesized M3A2X phases. The electrical conductivities of the 12 M3A2X phases are generally superior to those of corresponding classic M2AX phases, while their mechanical properties are slightly inferior. Through the comparison of bond strengths using the crystal orbital Hamilton population analysis, it has been discovered that M3A2X phases have a greater tendency to exfoliate into 2D MXenes than M2AX phases. Among them, the Zr3Se2C, Zr3S2C, and Sc3S2C phases exhibit the highest exfoliation potential. This study provides a comprehensive understanding of M3A2X phases, laying a solid foundation for future experimental synthesis and technological applications.

The potential applications of the B24N24 cage in Li-, Na-, K-, and Mg-ion batteries (LIBs, SIBs, PIBs, and MgIBs) were explored using density functional theory. Three potential adsorption sites of M/Mq+ (M=Li, Na, K, and Mg) on the B24N24 cage were identified: above the tetragonal, hexagonal, and octagonal rings. In the case of the octagonal ring, the storage capacity of MgIBs was found to be 536 mAhg-1, surpassing that of LIBs, SIBs, and PIBs with a value of 268 mAgh-1. Furthermore, the sequence of cell voltages (Vcell) generated by the B24N24 cage in ion batteries was determined as follows: MgIBs (3.46 V) andgt; LIBs (1.33 V) andgt; SIBs (1.11 V) andgt; PIBs (0.18 V). In both the tetragonal and hexagonal ring cases, the Vcell generated by the B24N24 cage were also highest in MgIBs, at 3.12 and 3.38 V, respectively. These findings indicate that the B24N24 cage could serve as a promising electrode material for MgIBs

Owing to metallic conductivity, tunable surface chemistry, mechanical flexibility, high surface area and chemical stability, MXenes have emerged as promising candidates for room-temperature gas sensors. In this study, gas sensing performances of the newly synthesized Hf3C2 MXene with oxygen termination toward a wide range of common molecules (NH3, H2O, H2S, H2, CO2, CO, CH4, N2 and NO) were investigated by first-principles density functional calculations. With the most negative adsorption energy, the highest charge transfer and the shortest adsorption distance, the adsorption of NH3 among the investigated gases causes the most significant changes in electrical conductivity and work function of Hf3C2O2 substrate, thus holds the biggest gas response. Only the NH3 exhibits strong chemical interactions with Hf3C2O2, and other gas molecules are weakly chemisorbed or physisorbed. All these indicate that Hf3C2O2 exhibits high selectivity and sensitivity to NH3. The adsorption energy of NH3 falls within the appropriate range for room-temperature gas sensors, enabling Hf3C2O2 to maintain NH3 sensitivity while also achieving a fast recovery time. Furthermore, giving that human exhaled breath does not affect, and may even enhance, the selectivity and sensitivity of Hf3C2O2 towards NH3, Hf3C2O2 can serve effectively as an NH3 sensor in human disease detection.

Developing efficient catalysts for the conversion of methane (CH4) to methanol (CH3OH) remains a critical challenge in the chemical industry, with significant implications for both energy production and environmental sustainability. This study pioneers the exploration of the Sc/Ti-Ti2CO2 single-atom catalysts (SACs) for this transformation, utilizing density functional theory (DFT) calculations. Notably, our findings reveal that Sc and Ti are uniquely stable on the Ti2CO2 MXene surface, a discovery that could inform future catalyst designs. We also demonstrate that while CH4 weakly physisorbs on the Sc/Ti-Ti2CO2 surface, N2O molecules decompose directly into N-2 and highly reactive O* species, which bind with Sc/Ti to drive the catalytic process. The oxidation of CH4 proceeds in two steps: CH4 + O* -> CH3* + OH* with reaction barriers of 0.58 eV (Sc) and 1.38 eV (Ti), followed by CH3* + OH* -> CH3OH with barriers of 1.5 eV (Sc) and 1.61 eV (Ti). Importantly, the low desorption energy of CH3OH, especially on Sc (0.85 eV), highlights the exceptional catalytic potential of Sc/Ti2CO2 for the direct conversion of CH4 to CH3OH. These results not only underscore the feasibility of using MXene-based SACs for CH4 oxidation but also provide a theoretical foundation for the development of highly efficient catalysts in this domain.

Amine-modified SiO2 aerogel (AMSA) has shown tremendous potential in CO2 capture due to its unique three-dimensional network structure and excellent stability. However, it still faces many challenges in the preparation optimization, adsorption enhancement at low CO2 partial pressure, and mechanism elucidation. Hence, in this paper, the response surface methodology is employed for the first time and the optimal preparation conditions for AMSA are determined. A regression model is successfully established to accurately predict the CO2 adsorption capacity of AMSA under different synthesis conditions (with a relative error of only 0.98 %). Additionally, the AMSA prepared at optimal conditions exhibits high CO2 adsorption capacity of 2.11 mmol/g and excellent stability (only decreased by 1.44 % after 8 cycles) at 10 % CO2 partial pressure, indicating enormous application potential. Notably, the CO2 adsorption mechanism by AMSA at different temperatures and partial pressures are revealed in detail through fitting with the Freundlich isotherm and the double-exponential model, as well as thermodynamic parameter calculations. Firstly, the CO2 adsorption behavior belongs to the multi-layer adsorption behavior with uneven energy of active sites. Secondly, the CO2 adsorption capacity and rate are jointly controlled by molecular motion and chemical reaction equilibrium, diffusion and chemical reaction steps, respectively. Finally, the adsorption process is exothermic and spontaneous, and the level of disorder decreases at the gas-solid interface. This study not only achieves efficient adsorption of low-pressure CO2, but also deepens the understanding of gas-solid interface adsorption mechanisms, providing scientific basis and technological support for the development of novel efficient AMSA adsorbent materials.