Iron single atom catalysts (FeN4) hosted in the micropores of N‐doped carbons offer excellent performance for the oxygen reduction reaction (ORR). Achieving a high density of FeN4 sites accessible ...for ORR has proved challenging to date. Herein, a simple surface NaCl‐assisted method towards microporous N‐doped carbon electrocatalysts with an abundance of catalytically accessible FeN4 sites is reported. Powder mixtures of microporous zeolitic imidazolate framework‐8 and NaCl are first heated to 1000 °C in N2, with the melting of NaCl above 800 °C creating a highly porous N‐doped carbon product (NC‐NaCl). Ferric (Fe3+) ions are then adsorbed onto NC‐NaCl, with a second pyrolysis stage at 900 °C in N2 yielding a porous Fe/NC‐NaCl electrocatalyst (Brunauer–Emmett–Teller surface area, 1911 m2 g−1) with an excellent dispersion and high density of accessible surface FeN4 sites (26.3 × 1019 sites g−1). The Fe/NC‐NaCl electrocatalyst exhibits outstanding ORR performance with a high half‐wave potential of 0.832 V (vs reversible hydrogen electrode) in 0.1 m HClO4. When used as the ORR cathode catalyst in a 1.0 bar H2‐O2 fuel cell, Fe/NC‐NaCl offers a high peak power density of 0.89 W cm−2, ranking it as one of the most active M‐N‐C materials reported to date.
A molten NaCl‐assisted synthesis method is developed for the preparation of microporous Fe‐N‐C electrocatalysts rich in surface FeN4 active sites (26.3 × 1019 sites g−1). The obtained Fe/NC‐NaCl electrocatalyst offers outstanding performance for the oxygen reduction reaction, delivering a power density of 0.89 W cm−2 when applied as the cathode catalyst in a H2‐O2 proton exchange membrane fuel cell.
Hydrothermal liquefaction (HTL) is a thermochemical conversion technology that shows promising commercial potential for the production of biocrude oil from wet biomass. However, the inevitable ...production of the hydrothermal liquefaction aqueous phase (HTL-AP) acts as a double-edged sword: it is considered a waste stream that without additional treatment clouds the future scale-up prospects of HTL technology; on the other hand, it also offers potential as an untapped nutrient and energy resource that could be valorized. As more researchers turn to liquefaction as a means of producing renewable fuel, there is a growing need to better understand HTL-AP from a variety of vantage points. Specifically, the HTL-AP chemical composition, conversion pathways, energy valorization potential, and the interconnection of HTL-AP conversion with biofuel production technology are particularly worthy of investigation. This paper extensively reviews the impact of HTL conditions and the feedstock composition on the energy and elemental distribution of process outputs with specific emphasis on the HTL-AP. Moreover, this paper also compares and contrasts the current state of value-added products separation along with biological (biomass cultivation, anaerobic fermentation, and bioelectrochemical systems) and thermochemical (gasification and HTL) pathways to valorize HTL-AP. Furthermore, life cycle analysis (LCA) and techno-economic assessments (TEA) are performed to appraise the environmental sustainability and economic implications of these different valorization techniques. Finally, perspectives and challenges are presented and the integration approaches of HTL-AP valorization pathways with HTL and biorefining are explored.
Gasification is a promising technology for reducing the volume of biowaste feedstock. Further, with the incorporation of steam this thermochemical treatment technology also concomitantly produces H2, ...a high value energy. This paper aims to summarize the status of biowaste gasification technology and detail the benefits and limitations of different gasification processes, especially for biowaste. First, we compare steam with other gasification agents (oxygen and air) to understand the specific effects of gasification agents on the resulting gas quality and quantity. Second, influencing process factors (reactor configurations, temperature, steam to biomass ratio, and catalyst incorporation) are evaluated in terms of their impact on the resulting H2/CO ratio, gas heating value, gas yield, tar yield, and energy recovery. Third, commercial biowaste gasification applications are detailed and the economics and societal impacts are elucidated. Finally, the current challenges facing the field of gasification and the future outlooks of this technology for reducing biowaste are presented.
Plastic waste is an emerging environmental issue for our society. Critical action to tackle this problem is to upcycle plastic waste as valuable feedstock. Thermochemical conversion of plastic waste ...has received growing attention. Although thermochemical conversion is promising for handling mixed plastic waste, it typically occurs at high temperatures (300–800 °C). Catalysts can play a critical role in improving the energy efficiency of thermochemical conversion, promoting targeted reactions, and improving product selectivity. This Review aims to summarize the state‐of‐the‐art of catalytic thermochemical conversions of various types of plastic waste. First, general trends and recent development of catalytic thermochemical conversions including pyrolysis, gasification, hydrothermal processes, and chemolysis of plastic waste into fuels, chemicals, and value‐added materials were reviewed. Second, the status quo for the commercial implementation of thermochemical conversion of plastic waste was summarized. Finally, the current challenges and future perspectives of catalytic thermochemical conversion of plastic waste including the design of sustainable and robust catalysts were discussed.
Thermochemical conversion: Plastic waste is one of the most critical issues in recent years. Upcycle plastic waste as valuable feedstock has attracted huge attention. This Review summarizes thermochemical conversion methods that can convert plastic waste into energy, chemicals, and value‐added materials. It also highlights the recent development of catalytic thermochemical conversions and the current challenges of catalytic thermochemical conversion of plastic waste.
•Hydrothermal liquefaction (HTL) of microalgae C. pyrenoidosa and S. platensis.•Characterization of bio-crude oils and aqueous fractions during HTL process.•General reaction network for HTL of C. ...pyrenoidosa and S. platensis.•Specific reaction pathways for HTL of lipid, protein and non-fibrous carbohydrate.
Low-lipid microalgae can be successfully converted to bio-crude oil in a hydrothermal liquefaction (HTL) environment. This study examined the behavior of hydrothermal liquefaction of two low-lipid content microalgae in subcritical water between 200°C and 320°C at 20°C intervals. Under these conditions, the chemical composition and functional groups for the bio-crude oil and aqueous fraction were analyzed. Results indicated that reaction temperature greatly affected the distribution of chemical composition and functional groups of HTL bio-crude oil and aqueous fraction. The bio-crude oil with a higher percentage of aliphatic functional groups was obtained at higher reaction temperatures (280–320°C). Besides, the aqueous fraction recovered under the same operating conditions had a lower concentration of nitrogenous organic compounds (NOCs) with two or more methyl groups. The general reaction network for HTL of low-lipid microalgae was proposed. The specific reaction pathways for microalgae substrates were analyzed in terms of lipid, protein and non-fibrous carbohydrate based on the spectral analysis.
Abstract
Polypropylene (PP) and poly(ethylene terephthalate) (PET) are plastics commonly used for packaging because of their excellent barrier and mechanical properties. The properties of these ...plastics are often diminished after mechanical recycling, inevitably causing down‐cycling. This problem is exacerbated when different kinds of polymers mix. Aramid nanofibers have the potential to improve the mechanical properties of polymers due to their excellent mechanical properties but their poor dispersion in polymers is a challenge. Grafting polymers onto nanofibers can help address this challenge. In this work, different loading levels (1%, 2%, and 5%) of polymer grafted aramid nanofibers (ANFs) are blended with waste PP/PET (90/10), simulating a PP waste stream containing traces of PET contaminants. Scanning electronic microscopy, rheology, and differential scanning calorimetry results show the affinity of PP functionalized aramid nanofibers (PP_ANF) towards the PP matrix. At 1 wt% of the nanofiber, the size of the PET droplets in the PP matrix of the PP_ANF blend range from 0.2 to 2.0 μm while that of unmodified ANF and PET_ANF blends are in the range of 0.1–6.2 and 0.5–7.4 μm, respectively. In summary, polymer grafted ANFs have the tendency of improving properties of its like polymers due to similarity in the grafting polymer and the polymer matrix.
HLA‐G is considered as an immune checkpoint protein and a tumor‐associated antigen. In the previous work, it is reported that CAR‐NK targeting of HLA‐G can be used to treat certain solid tumors. ...However, the frequent co‐expression of PD‐L1 and HLA‐G) and up‐regulation of PD‐L1 after adoptive immunotherapy may decrease the effectiveness of HLA‐G‐CAR. Therefore, simultaneous targeting of HLA‐G and PD‐L1 by multi‐specific CAR could represent an appropriate solution. Furthermore, gamma‐delta T (γδT) cells exhibit MHC‐independent cytotoxicity against tumor cells and possess allogeneic potential. The utilization of nanobodies offers flexibility for CAR engineering and the ability to recognize novel epitopes. In this study, Vδ2 γδT cells are used as effector cells and electroporated with an mRNA‐driven, nanobody‐based HLA‐G‐CAR with a secreted PD‐L1/CD3ε Bispecific T‐cell engager (BiTE) construct (Nb‐CAR.BiTE). Both in vivo and in vitro experiments reveal that the Nb‐CAR.BiTE‐γδT cells could effectively eliminate PD‐L1 and/or HLA‐G‐positive solid tumors. The secreted PD‐L1/CD3ε Nb‐BiTE can not only redirect Nb‐CAR‐γδT but also recruit un‐transduced bystander T cells against tumor cells expressing PD‐L1, thereby enhancing the activity of Nb‐CAR‐γδT therapy. Furthermore, evidence is provided that Nb‐CAR.BiTE redirectes γδT into tumor‐implanted tissues and that the secreted Nb‐BiTE is restricted to the tumor site without apparent toxicity.
Elevated PD‐L1 in solid tumors increases the risk of immune escape from HLA‐G‐CAR cell therapy. The bicistronic mRNA construct that drives PD‐L1 Nb‐BiTE and HLA‐G Nb‐CAR in γδT cells via electroporation is designed to address this issue. This Nb‐CAR.BiTE‐γδT therapy can overcome HLA‐G and PD‐L1 dilemma and even kill tumor cells with inadequate antigen expression, resulting in potent anti‐tumor activity without apparent toxicity.
•Aqueous products from hydrothermal liquefaction (HTL-ap) are formed in large amounts.•HTP-ap may contain substances toxic to several organisms.•Further reuse or treatment of the HTL-ap is ...necessary.•Anaerobic digestion of HTL-ap could be conducted.
This study examined the chemical characteristics and the anaerobic degradability of the aqueous product from hydrothermal liquefaction (HTL-ap) from the conversion of mixed-culture algal biomass grown in a wastewater treatment system. The effects of the HTL reaction times from 0 to 1.5h, and reaction temperatures from 260°C to 320°C on the anaerobic degradability of the HTL-ap were quantified using biomethane potential assays. Comparing chemical oxygen demand data for HTL-ap from different operating conditions, indicated that organic matter may partition from organic phase to aqueous phase at 320°C. Moderate lag phase and the highest cumulative methane production were observed when HTL-ap was obtained at 320°C. The longest lag phase and the smallest production rate were observed in the process fed with HTL-ap obtained at 300°C. Nevertheless, after overcoming adaptation issues, this HTL-ap led to the second highest accumulated specific methane production. Acetogenesis was identified as a possible rate-limiting pathway.
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•Ni/P25 TiO2 and Au/P25 TiO2 afford similar H2 production rates in alcohol-water mixtures.•Ni/P25 TiO2 outperforms Au/P25 TiO2 in methanol-water mixtures under UV excitation.•H2 ...production rates depend on the alcohol hole scavenger and alcohol concentration.•At 10 vol%, rates follow the order glycerol > ethylene glycol > methanol > ethanol.•At 40 vol%, rates follow the order methanol > ethylene glycol > glycerol > ethanol.
This study systematically compares the performance of 0.5 wt% Ni/P25 TiO2 and 2 wt% Au/P25 TiO2 photocatalysts for H2 production in alcohol-water mixtures under UV excitation. HRTEM, XANES and EXAFS confirmed the presence of 5–8 nm Ni0 and Au0 nanoparticles on the surface of the photocatalysts. H2 production tests were conducted in various alcohol-water systems (0–100 vol%), using methanol, ethanol, ethylene glycol and glycerol. The Ni/P25 TiO2 and Au/P25 TiO2 photocatalysts demonstrated remarkably similar performance for hydrogen production in all the alcohol-water systems tested. At low alcohol concentrations (15 vol% or less), H2 production rates followed the order glycerol > ethylene glycol > methanol > ethanol, whilst at higher alcohol concentrations methanol (optimum 40 vol%) and ethanol (optimum 80–90 vol%) afforded the highest rates. Rates depended on the polarity and oxidation potential of the alcohol. Further, anatase-rutile heterojunctions in P25 TiO2 were found to greatly enhance H2 production.
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