Metal Surface Area Research Articles

Hydrodeoxygenation of C3–4 polyols to C3–4 diols over carbon-supported bimetallic MgCu@C catalysts prepared from ion exchange resin

The selective hydrodeoxygenation (HDO) of C3–4 polyols (glycerol and erythritol) to value-added diol products was investigated over a series of Cu-based catalysts, namely, carbon-supported monometallic Cu@C and bimetallic MgCu@C prepared by using a weakly acidic cation-exchange resin as the carbon support precursors. High metal loading (> 50 wt%) and small metal particle size (< 15 nm) were realized by the catalyst prepared from ion-exchange resin. The addition of Mg decreased Cu particle size (10.0–13.5 nm) and improved metal dispersion. The largest metal surface area was achieved for the MgCu@C catalyst with Mg/Cu molar ratio of 1/9. Furthermore, HDO of C3–4 polyols was performed over the prepared catalysts at relatively low temperature (180 °C) under low initial H2 pressure (1.2 MPa). Over the MgCu@C catalyst with a nominal Cu/Mg atomic ratio of 9/1, a C3 polyol conversion of 94.0 C mol% was obtained with a high selectivity towards 1,2-propanediol (94.3 C mol%), while a low erythritol conversion of 18.75 C mol% with a selectivity toward butanediols of 43.0 C mol% was achieved after 360 h reaction. The different effects of the Mg addition on catalytic activity to C3 and C4 polyol HDO were likely attributed to the different reaction mechanism. The dehydration-hydrogenation mechanism was proposed for C3 HDO over Cu@C and MgCu@C, in which the addition of Mg species promoted the dehydration of glycerol to produce hydroxyacetone followed by the hydrogenation of hydroxyacetone to 1,2-propanediol.

Fluorescence sensor based on molecularly imprinted polymers and core–shell upconversion nanoparticles@metal–organic frameworks for detection of bovine serum albumin

A novel strategy for sensing protein was proposed through combining the high selectivity of molecular imprinting technology with the excellent upconversion fluorescence of upconversion nanoparticles (UCNPs) and high specific surface area of metal–organic frameworks (MOFs). Herein, the UCNPs acted as signal reporter and MOFs were introduced to increase the rate of mass transfer. The UCNPs@MIL-100 as support material was prepared via a step-by-step method. The imprinted material-coated UCNPs@MIL-100 (UCNPs@MIL-100@MIPs) were obtained by sol–gel technique. The results showed that as the increase of the template protein concentration, the fluorescence intensity of UCNPs@MIL-100@MIPs quenched gradually, and the imprinting factor was 2.90. The linear in the range of 1.00 to 8.00 μM, and the detection limit was 0.59 μM. Therefore, the novel optosensing material is very promising for future applications.

Dual nanozyme based on ultrathin 2D conductive MOF nanosheets intergraded with gold nanoparticles for electrochemical biosensing of H2O2 in cancer cells

The development of facile, rapid and cost-effective strategies for sensitive detection of cancer biomarkers in human samples is of great significance for early diagnosis of malignant tumors related diseases. In this work, we develop a high-performance electrochemical biosensor based on highly active dual nanozyme amplified system, i.e., ultrathin two-dimension (2D) conductive metal–organic framework (C-MOF) nanosheets (NSs) decorated with high-density ultrafine gold nanoparticles (Au-NPs), and explore its application in sensitive detection of cancer biomarker H2O2 in live cells. The C-MOF NSs {i.e., Cu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene)-NSs} provide large surface area and abundant active open metal sites (Cu–O4), which could improve the catalytic activity of Cu-HHTP-NSs towards H2O2. Moreover, abundant exposed O atoms also serve as anchor sites for the deposition of high-density ultrafine Au-NPs (∼3 nm) without agglomeration. Owing to the synergistic contributions of high catalytic activity of Cu-HHTP-NSs and Au-NPs as well as their unique structural and electrical properties, the as-prepared nanohybrid modified electrode exhibits good sensing performances to H2O2 with an extremely low detection limit of 5.6 nM (3σ rules) and a high sensitivity of 188.1 μA cm−2 mM−1. Furthermore, the proposed nanozymatic electrochemical biosensor has been applied in real-time tracking H2O2 released from different human colon cells to identify colon cancer cells from normal colon epithelial cell, which demonstrates its great prospect for early diagnosis and management of various cancer diseases.

Synthesis of High Surface Area-Group 13-Metal Oxides via Atomic Layer Deposition on Mesoporous Silica.

The atomic layer deposition of gallium and indium oxide was investigated on mesoporous silica powder and compared to the related aluminum oxide process. The respective oxide (GaOx, InOx) was deposited using sequential dosing of trimethylgallium or trimethylindium and water at 150 °C. In-situ thermogravimetry provided direct insight into the growth rates and deposition behavior. The highly amorphous and well-dispersed nature of the oxides was shown by XRD and STEM EDX-mappings. N2 sorption analysis revealed that both ALD processes resulted in high specific surface areas while maintaining the pore structure. The stoichiometry of GaOx and InOx was suggested by thermogravimetry and confirmed by XPS. FTIR and solid-state NMR were conducted to investigate the ligand deposition behavior and thermogravimetric data helped estimate the layer thicknesses. Finally, this study provides a deeper understanding of ALD on powder substrates and enables the precise synthesis of high surface area metal oxides for catalytic applications.

Reductive amination of cyclohexanol/cyclohexanone to cyclohexylamine using SBA-15 supported copper catalysts

Amination of cyclohexanol was investigated in vapour phase over copper catalysts supported on mesoporous SBA-15. The different products identified during reductive amination of cyclohexanol reaction were cyclohexanone, cyclohexylamine, along with small amounts of N-Cyclohexylidinecyclohexylamine and dicyclohexylamine. Among several catalysts tested for the reductive amination, 5% Cu supported on SBA-15 exhibited better catalytic performance than other catalysts with 36% selectivity towards cylclohexylamine at 80% cyclohexanol conversion. The optimum reaction conditions employed to achieve the best catalyst performance were at 250 °C, 0.1 MPa of H2/NH3, TOS-10h. The active Cu sites, acidity of the catalyst, and effect of reaction parameters play a pivotal role in the reductive amination reaction. The prepared catalysts were characterized by XRD, BET, SEM, H2-TPR and NH3-TPD. The dispersion of Cu, particle size, and metal surface area (m2/g) calculated from pulse N2O decomposition method. TPR findings reveal the presence of substantially dispersed copper oxide species at lower loadings which is easily reducible than the bulk copper oxide species found at higher Cu loadings. The acidity measurements by NH3-TPD analysis suggest that the maximum acidic strength was obtained at 5 wt% copper on porous SBA-15, and decreased with Cu loadings. The catalytic properties are well in agreement with the findings of catalysts characterization.

Ce-doped cobalt aluminate catalysts for the glycerol hydrodeoxygenation (HDO) with in-situ produced hydrogen

In this study, the hydrodeoxygenation (HDO) of glycerol with in-situ produced H2, via aqueous-phase reforming, was investigated over Ce-doped CoAl2O4 catalysts synthesized by coprecipitation. The catalytic runs were performed at 50 bar/260 ºC for 3 h TOS in a fixed bed reactor. The synthesized catalysts were extensively characterized to better understand the effect of physicochemical and surface characteristics on the catalytic performance. The results revealed that doping with Ce increases the population and strength of acid centers, which results in a higher selectivity towards deoxygenated liquid products. Ce-doped catalysts exhibited higher yield to hydroxyacetone and 1,2-propanediol. Post-reaction characterization revealed a decrease of the metallic surface area, mainly due to alumina coating, and to a lesser extent, due to the oxidation and leaching of the cobalt.

Tailoring the selectivity of Cu-based catalysts in the furfural hydrogenation reaction: Influence of the morphology of the silica support

Cu nanoparticles were incorporated on different porous silica supports (commercial silica, SBA-15 synthesized both at room temperature and under hydrothermal conditions, and mesocellular foam) by the strong electrostatic adsorption method and tested in the gas-phase furfural hydrogenation for the production of furfuryl alcohol and 2-methylfuran, being the latter a promising biofuel. The incorporated copper species provided metal particle sizes lower than 5 nm in all cases. However, different catalytic behaviors, both in terms of conversion and selectivity, were detected due to the morphology and textural properties of each support. Cu over commercial silica was more prone to suffer from deactivation, and it provided higher furfuryl alcohol yields, probably due to its higher acidity and lower metallic surface area. On the other hand, the agglomeration of Cu nanoparticles together with larger pore sizes complicated the access of furfural to the active sites using the hydrothermal SBA-15 support, thus decreasing the activity. In contrast, the addition of fluoride in the synthesis of mesoporous silica, which shortened the length of the silica channels (mesocellular foam), facilitated the furfural access and provided both higher metallic surface area and lower acidity. This fact led to a more gradual deactivation, still attaining high values of furfural conversion and 2-methylfuran yield (95 and 76%, respectively) after 5 h at 190 °C. However, Cu over mesocellular foam changed its selectivity pattern along 48 h and after regeneration, increasing the furfuryl alcohol selectivity due to the decreased number of available active sites.

Enhanced CO2 Methanation Activity of Sm0.25Ce0.75O2-δ-Ni by Modulating the Chelating Agents-to-Metal Cation Ratio and Tuning Metal-Support Interactions.

Highly active and selective CO2 methanation catalysts are critical to CO2 upgrading, synthetic natural gas production, and CO2 emission reduction. Wet impregnation is widely used to synthesize oxide-supported metallic nanoparticles as the catalyst for CO2 methanation. However, as the reagents cannot be homogeneously mixed at an atomic level, it is challenging to modulate the microstructure, crystal structure, chemical composition, and electronic structure of catalysts via wet impregnation. Herein, a scalable and straightforward catalyst fabrication approach has been designed and validated to produce Sm0.25Ce0.75O2-δ-supported Ni (SDC-Ni) as the CO2 methanation catalyst. By varying the chelating agents-to-total metal cations ratio (C/I ratio) during the catalyst synthesis, we can readily and simultaneously modulate the microstructure, metallic surface area, crystal structure, chemical composition, and electronic structure of SDC-Ni, consequently fine-tuning the oxide-support interactions and CO2 methanation activity. The optimal C/I ratio (0.1) leads to an SDC-Ni catalyst that facilitates C-O bond cleavage and significantly improves CO2 conversion at 250 °C. A CO2-to-CH4 yield of >73% has been achieved at 250 °C. Furthermore, a stable operation of >1500 hours has been demonstrated, and no degradation is observed. Extensive characterizations were performed to fundamentally understand how to tune and enhance CO2 methanation activity of SDC-Ni by modulating the C/I ratio. The correlation of physical, chemical, and catalytic properties of SDC-Ni with the C/I ratio is established and thoroughly elaborated in this work. This study could be applied to tune the oxide-support interactions of various catalysts for enhancing the catalytic activity.

General Synthetic Strategy to Ordered Mesoporous Carbon Catalysts with Single-Atom Metal Sites for Electrochemical CO2 Reduction.

The electrochemical carbon dioxide reduction reaction (CO2 RR) is a transformative technology to reduce the carbon footprint of modern society. Single-site catalysts have been demonstrated as promising catalysts for CO2 RR, but general synthetic methods for catalysts with high surface area and tunable single-site metal composition still need to be developed to unambiguously investigate the structure-activity relationship crossing various metal sites. Here, a generalized coordination-condensation strategy is reported to prepare single-atom metal sites on ordered mesoporous carbon (OMC) with high surface areas (average 800m2 g-1 ). This method is applicable to a broad range of metal sites (Fe, Co, Ni, Cu, Pt, Pd, Ru, and Rh) with loadings up to 4wt.%. In particular, the CO2 RR to carbon monoxide (CO) Faradaic efficiency (FE) with Ni single-site OMC catalyst reaches 95%. This high FE is maintained even under large current density (>140mAcm-2 ) and in a long-term study (14h), which suits the urgently needed large-scale applications. Theoretical calculations suggest that the enhanced activity on single-atom Ni sites results from balanced binding energies between key intermediates, COOH and CO, for CO2 RR, as mediated by the coordination sphere.

Mesoporous nano Ni-Al2O3 catalyst for CO2 methanation in a continuously stirred tank reactor

Mesoporous nano Ni-Al2O3 catalysts were prepared by using Pluronic P123 (P123) and fatty alcohol polyoxyethylene ether (AEO-7) as structure directing agents (SDAs), and applied for CO2 methanation in a continuously stirred tank reactor (CSTR). Compared with NiAl-A prepared by using AEO-7 as SDA and NiAl-N without SDA, NiAl-P prepared by using P123 as SDA possesses ordered mesopores, high Ni dispersion, large metal surface area and amounts of adsorbed CO2, which benefits CO2 conversion. Under the conditions of 1.0 MPa, 300 °C and H2/CO2 ratio of 4, NiAl-P shows the highest CO2 conversion of 74.0% and CH4 yield of 73.6%.

Optimizing test approaches for the detection of exposed metal surfaces within a chromatographic flow path

It is critical to the success of any chromatography-based assay that the performance of the LC instrument be checked for its readiness and ability to perform the intended analysis. This includes gaging the suitability of a system to fulfill the purpose of different types of methods. One type of analysis that requires special consideration is the analysis of compounds which are prone to a particular form of non-specific binding, namely metal adsorption, where analytes interact and potentially adsorb to metal contained within the chromatographic flow path. For an analysis of compounds which are susceptible to metal adsorption, ideally a system suitability test would be performed to ensure there will not be any sample loss or detrimental peak shape effects resulting from potential analyte-to-metal interactions. To help chromatographers assess system inertness concerns like this, we have developed a method of testing LC systems for metal interactions using adenosine 5′-(α,β-methylene)diphosphate (AMPcP). This nucleotide analog has been confirmed to have a propensity to adsorb to titanium and stainless-steel frits and is resistant to hydrolysis and stable to long-term storage and repeat use (as is befitting of any reagent proposed for system suitability testing). AMPcP has been used in a flow injection test (no column in-line) to monitor for losses in recovery and peak shape perturbations that can potentially be present in any chromatography system manufactured with one or more metal based components. In this approach, sequential injections of AMPcP were made without a column and various peak attributes were monitored and ultimately correlated to the amount of metal surface area in the flow path. The ability of this method to discriminate between inert chromatographic surfaces versus exposed metal surfaces was verified by comparing peak areas, peak shapes, and injection repeatability for AMPcP using a UHPLC equipped with MP35N metal alloy components versus an equivalent UHPLC equipped with an ethylene bridged hybrid organic-inorganic surface (or so-called hybrid surface technology). Injections of caffeine were also explored to establish a negative control for this system suitability measurement. Caffeine does not interact with metal surfaces and can therefore give an instrument specific representation of peak shape and dispersion as well as an indication of overall mechanical system performance. Additionally, replicate injections of AMPcP and caffeine onto a UHPLC partially configured with hybrid surface technology (HST) readily identified exposed metal surfaces through an increased peak area relative standard deviation as well as a reduction in absolute recovery. Finally, a novel visualization tool was developed to provide an alternative method of determining system inertness without having to perform chromatographic calculations but instead a graphical peak shape comparison between a negative control, caffeine, and the metal sensitive AMPcP test probe.

In situ growth of hierarchical bimetal-organic frameworks on nickel-iron foam as robust electrodes for the electrocatalytic oxygen evolution reaction

Evidence shows that self-supported electrocatalysts are crucial role to solving environmental and energy issues. In this study, self-supported 2D metal–organic framework (MOF) nanosheets grown in situ on nickel–iron foam (NFF) were prepared by a one-step solvothermal process. The hierarchical nanostructure possesses a high specific surface area and abundant metal sites, which are beneficial for electrocatalytic reactions. In the electrocatalytic oxygen evolution reaction (OER), the optimal NiFe(20Ni)-MOF/NFF can drive current densities of 10, 50 and 100 mA cm−2 at small overpotentials of 226, 277 and 294 mV, respectively. According to the characterization results, the OER performance is improved by the synergistic action of bimetals and the generation of hydroxides/oxyhydroxides. This work provides new insights into fabricating self-supported MOF-based electrodes for water splitting that are simple and highly efficient.

Strategic combination of metal–organic frameworks and C3N4 for expeditious photocatalytic degradation of dye pollutants

The potential of fabricated silver and bismuth Co-N-doped imidazolate embedded into graphitic nitride BiO-Ag(0)/C3N4@ZIF-67 for the degradation of Methylene blue (MB) and Congo red (CR) dyes have been reported. The synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy photoluminescence (PL) spectroscopy, and electrochemical impedance spectroscopy (EIS). The band gaps of ZIF-67, C3N4and composites were calculated using Tauc plot.Besides,it was revealed that incorporation of silver, bismuth, and C3N4 reduced the band gap energy to 2.2eV. The introduction of metallic species in the precursors promoted better charge separation behavior towards photogenerated electron and hole in the heterojunction composite. Two perilous organic dyes; MB and CR were degraded under natural sunlight irradiation. The photocatalytic efficiency of BiO-Ag(0)/C3N4@ZIF-67 for the removal of CR and MB significantly increased compared to bare ZIF-67. The enhanced photocatalytic activity of BiO-Ag(0)/C3N4@ZIF-67 is attributed to the higher surface area and Plasmon effect of noble silver metal. The solar light-triggered degradation of MB and CR yielded efficient efficiency of 96.5 and 90% for 10mg/L of dye solution each. Additionally, the effect of pH was evaluated for optimizing degradation of CR and MB dyes. The kinetics studies of both CR and MB were clarified according to Langmuir model. The reusability and quenching investigation of active species were carried out to discover find catalytic potential of the composite. Besides, possible dye degradation mechanism was proposed for BiO-Ag(0)/C3N4@ZIF-67. The obtained results indicated that solar-light triggered photocatalyst BiO-Ag(0)/C3N4@ZIF-67 can be employed as a promising approach for photocatalytic elimination of organic pollutants.

Size-dependent selectivity and activity of highly dispersed sub-nanometer Pt clusters integrated with P25 for CO2 photoreduction into methane fuel

Integration of sub-nanometer–sized Pt cocatalysts on semiconductor materials is a promising approach to improve the activity and selectivity of CO2 photoreduction. However, the practical realization of such an integrated catalyst is a challenging task. We rationally integrated sub-nanometer Pt nanoclusters (Pt NCs) on the surface of commercial P25 catalyst by adjusting the amount of Pt loading. The lateral reduction in the size of Pt NCs resulted in high metal dispersion, increased active metal surface area, better CO2 adsorption, and hindered photoexcited charge-carrier recombination. The sub-nanometer Pt NCs integrated with P25 with a weight percentage of 0.5% (Pt-NC/P25-0.5) exhibited exceptional CO2 photoreduction activity for CH4 production and excellent stability during successive test runs. This catalyst outperformed its counterparts with larger Pt NCs and several previously reported state-of-the-art photocatalysts in terms of CH4 generation. Importantly, compared to its counterparts, Pt-NC/P25-0.5 had a higher proportion of edge and corner sites, which have a strong affinity for CO molecules, resulting in a high CH4 selectivity of 95% against H2. The size-dependent selectivity and activity of Pt NCs for CO2 reduction demonstrated in this study offer insights into the development of sub-nanometer metal-based catalysts for photocatalytic energy applications.

Machine Learning and Natural Language Processing Enable a Data-Oriented Experimental Design Approach for Producing Biochar and Hydrochar from Biomass

Carbon functional materials (CFMs) such as biochar and hydrochar can be obtained from hundreds of biomass precursors varying from urban sludge to agriculture wastes. They can be produced through tens of synthesis methods and postsynthesis processing steps tuned at specific conditions (e.g., temperature, time, and chemical concentrations). To achieve a “rational design” platform for a system with a high dimensional parameter space such as CFMs, we processed 10,975 scientific articles (from years 2000 to 2020) related to the subject with automatic reading–interpreting–extracting computational routines (namely, the a.RIX engine). The a.RIX engine automatically recognized more than a hundred precursors, among which wheat straw, rice husk, and rice straw were the most studied for CFM synthesis and application in agriculture (e.g., as an amendment), as fuel (energy generation), and as an adsorbent. Parameters related to the CFMs’ synthesis conditions, such as carbonization temperature and time, and parameters related to CFMs’ properties, such as surface area and heavy metals adsorption capacity, can also be extracted from the articles. Correlations between the CFM precursors and synthesis conditions indicated very little statistical difference between the carbonization temperature and time used for the CFMs’ synthesis from different precursors. Essentially, precursors are carbonized at temperatures varying from 100 to 900 °C for 30 min to 6 h using pyrolysis, hydrothermal carbonization, and gasification. When focusing the analysis on just CFMs produced by pyrolysis (biochar), we observed that peanut shells can produce materials with higher surface areas than other precursors (P < 0.05). When performing correlations between biochar synthesis conditions and their properties, general trends can be confirmed: (i) the higher the carbonization temperature, the lower the H/C and O/C ratios, and (ii) the increase in the surface area can be achieved by preserving a high aromatic degree (low H/C ratio) and a low oxidation level (low O/C ratio). However, a deeper understanding of the relation between CFM synthesis/postsynthesis methods and the resulting properties can only be achieved using clustering algorithms (e.g., k-means) and complex network analysis. The a.RIX engine groups articles describing optimized synthesis conditions and CFM properties (e.g., low carbonization temperature, low carbonization time, and large surface area and adsorption capacity) and automatically recognizes the synthesis/postsynthesis steps used for these groups. The program efficiently recognized that precursors such as peanut shells can be converted into highly porous biochar by using experimental routes such as “pyrolysis” → “activation” → “drying” → “ashing” → “washing” → “filtration.” With this approach, we show that a noncomputational review of scientific articles for materials with a huge parameter space such as CFMs is largely obsolete. Finally, taken together, the results provide a powerful platform for data-oriented experimental design of CFMs produced from biomass.

Selective Hydrogenation of Glycolic Acid to Renewable Ethylene Glycol over Supported Ruthenium Catalysts

AbstractThe production of industrially demanded polymer precursor ethylene glycol (EG) from biomass‐accessible aqueous glycolic acid (GA) was investigated in this study. The systematic investigation of different active metals as well as, for the first time, various support materials revealed Ru/TiO2 and Ru/ZrO2 to be the most active catalysts in the heterogeneously catalyzed reduction of GA with molecular H2. Catalytic activity is enhanced by facilitated reduction of the active Ru species due to metal‐support interactions. An assessment of several other catalyst properties (metal surface area, acid properties, porosity) revealed that high metal dispersion is also beneficial. Up to 94 % GA conversion and 95 % selectivity for EG were obtained under optimized and mild reaction conditions (105 °C, 60 bar H2 pressure, 23 h, Ru/TiO2 as catalyst). This shows that the heterogeneously catalyzed reduction of biomass‐derived aqueous GA solutions can be a promising alternative for the renewable production of EG.

Trimetallic metal-organic frameworks (Fe, Co, Ni-MOF) derived as efficient electrochemical determination for ultra-micro imidacloprid in vegetables

The excessive use of imidacloprid in agricultural production leads to a large number of residues that seriously threaten human health. Therefore, the detection of imidacloprid has become very important. But how to quantitatively detect imidacloprid at ultra-low levels is the main challenges. In this work, trimetallic metal-organic frameworks Fe, Co, Ni-MOF (FCN-MOF) is in situ prepared on nickel foam (NF) and then used to make an electrochemical sensor in the detection of imidacloprid. FCN-MOF exhibits the characteristics of ultra-micro concentration detection for imidacloprid with high specific surface area and rich active metal centers. The high conductivity and 3D skeleton structure of the NF electrode enhance the contact site with imidacloprid and promote the transmission of electrons efficiently. All results show that the prepared electrochemical sensor has the advantages of ultra-low detection limits (0.1 pM), wide linear detection ranges (1–5 × 107 pM) and good sensitivity (132.91 μA pM‒1 cm‒2), as well as good reproducibility, excellent anti-interference ability, and fantastic stability. Meanwhile, the electrochemical sensor is used to determine imidacloprid in lettuce, tomato, and cucumber samples with excellent recovery (90%–102.7%). The novel electrochemical sensor is successfully applied to the ultra-micro detection of imidacloprid in vegetables, which provides a new way for the efficient monitoring of imidacloprid in agriculture.

Adsorption of CO2 by alkali metals and weak alkali rare earth metals supported on aluminum pillared diatomite

In this study, aluminum pillared diatomite loaded with alkali metals and weak alkali rare earth metals was prepared by impregnation method with cheap and abundant diatomite as raw material. Aluminum pillared diatomite loaded with alkali metals Cs, K, Na, Li and aluminum pillared diatomite loaded with weakly alkaline rare earth metals La, Nd, Tm were prepared respectively. Its physicochemical properties were studied by XRPD and N2 adsorption/desorption techniques, and characterized by thermogravimetric analysis, CO2 temperature programmed desorption and FTIR. The results show that the adsorption capacity of 5Cs/Al-PILC for CO2 is the highest, which is 2.355 mmol/g. The specific surface area and porosity of diatomite were improved by aluminum pillared modification, but the specific surface area and micropore content of metal loaded diatomite decreased slightly. The effect of alkalinity is greater than that of micropore amount. The adsorption performance of aluminum pillared diatomite adsorbent is affected by the synergistic effect of specific surface area, total micropore volume and alkalinity. Alkalinity is the main factor affecting the adsorption capacity. The adsorption process of CO2 on the sample is mainly chemical adsorption. The addition of appropriate amount of metal can enhance the alkalinity of the sample, and the adsorbed CO2 exists in the form of bicarbonate and carbonate. The adsorbent made from diatomite has low cost, can be used in industrial production, and has broad development prospects.

Recent Advancements in the Synthesis and Application of Carbon-Based Catalysts in the ORR

Fuel cells are a promising alternative to non-renewable energy production industries such as petroleum and natural gas. The cathodic oxygen reduction reaction (ORR), which makes fuel cell technology possible, is sluggish under normal conditions. Thus, catalysts must be used to allow fuel cells to operate efficiently. Traditionally, platinum (Pt) catalysts are often utilized as they exhibit a highly efficient ORR with low overpotential values. However, Pt is an expensive and precious metal, posing economic problems for commercialization. Herein, advances in carbon-based catalysts are reviewed for their application in ORRs due to their abundance and low-cost syntheses. Various synthetic methods from different renewable sources are presented, and their catalytic properties are compared. Likewise, the effects of heteroatom and non-precious metal doping, surface area, and porosity on their performance are investigated. Carbon-based support materials are discussed in relation to their physical properties and the subsequent effect on Pt ORR performance. Lastly, advances in fuel cell electrolytes for various fuel cell types are presented. This review aims to provide valuable insight into current challenges in fuel cell performance and how they can be overcome using carbon-based materials and next generation electrolytes.

Steam reforming of methanol for hydrogen production over attapulgite-based zeolite-supported Cu-Zr catalyst

The methanol steam reforming (MSR) was one of the promising technologies for high-efficiency hydrogen production. The key issue for MSR was the development of catalysts. In this paper, the Cu-Zr components supported on the attapulgite-based zeolite (AZ) was prepared and applied into MSR reaction. MSR activity test demonstrated the synthesized micropore and mesopore channels in AZ enhanced the catalytic performance through promoting the heat and mass transfer. Various characterizations such as N2 adsorption–desorption, XRD, H2-TPR, XPS, SEM, HRTEM, H2/CO2-TPD, H2 pulse chemisorption and TGA confirmed Zr addition significantly increased the distribution of active metal particles and metallic surface area and facilitated the formation of Cu0/Cu+-ZrOxHy interface sites. Among the prepared catalysts, 1Cu1Zr/AZ catalyst possessed the maximum Cu0/Cu+-ZrOxHy interface sites and metallic surface area, therefore it exhibited the best catalytic performance for MSR, and its hydrogen productivity reached to 655.1 mmol/gcat/h. In addition, the Cu0/Cu+-ZrOxHy interface sites in Zr-modified Cu/AZ catalysts inhibited the active metal sintering and coke formation. The possible mechanism of MSR over 1Cu1Zr/AZ was proposed, in which Cu0/Cu+ species promoted the decomposition of methanol and intermediates, meanwhile, the Cu0/Cu+-ZrOxHy interface sites helped to continuously provide the –OH groups through steam activation by hydroxylated Zr species. These cooperative effects promoted the oxidation of intermediates and water–gas shift reaction, resulting in producing more H2 and CO2. This work offers a possibility for preparing available and economical attapulgite-based zeolite-supported Cu-Zr Catalyst for MSR.