Deep-Eutectic Solvents Derived Nitrogen-Doped Graphitic Carbon as a Superior Electrocatalyst for Oxygen Reduction

Electrocatalysis in deep eutectic solvents: from fundamental properties to applications

Electrocatalysis stands out as a promising avenue for synthesizing high-value products with minimal environmental footprint, aligning with the imperative for sustainable energy solutions. Deep eutectic solvents (DESs), renowned for their eco-friendly, safe, and cost-effective nature, present myriad advantages, including extensive opportunities for material innovation and utilization as reaction media in electrocatalysis. This review initiates with an exposition on the distinctive features of DESs, progressing to explore their applications as solvents in electrocatalyst synthesis and electrocatalysis. Additionally, it offers an insightful analysis of the challenges and prospects inherent in electrocatalysis within DESs. By delving into these aspects comprehensively, this review aims to furnish a nuanced understanding of DESs, thus broadening their horizons in the realm of electrocatalysis and facilitating their expanded application.

N/Se co-doped porous carbon catalyst derived from a deep eutectic solvent and chitosan as green precursors: Investigation of catalytic activity for metal-free oxidation of alcohols

Heteroatom-doped porous carbon-based materials with high surface area compared to their metal-based homologs are considered environmentally friendly and ideal catalysts for organic reactions. In this paper, a new method for the convenient fabrication, cost-effective, and high efficiency of nitrogen/selenium co-doped porous carbon-based catalysis (marked as N/SePC-T) was designed. The N/SePC-T catalysts were created from the direct pyrolysis of a eutectic solvent containing choline chloride/urea as the nitrogen-rich carbon source, selenium dioxide as a source of heteroatom and chitosan as a secondary carbon source in different temperatures (T). The efficacy of the carbonization temperature on the pore structure, morphology, and catalytic activity of the N/SePC-T materials was investigated and displayed, the N/SePC-900 (having a surface area of 562.01 m2/g and total pore volume of 0.2351 cm3 g-1) has the best performance. The morphology, structure, and physicochemical properties of N/SePC-900 were characterized using various analyses including XRD, TEM, TGA, FE-SEM, EDX, FT-IR, XPS, and Raman. The optimized N/SePC-900 catalyst indicated excellent catalytic performance in the oxidation of benzylalcohols to corresponding aldehydes in very mild conditions.

ZIF-8 derived defect-rich nitrogen-doped carbon with enhanced catalytic activity for efficient non-radical activation of peroxydisulfate

The non-radical oxidation processes of persulfate activation by carbon materials have shown great potential for industrial and saline wastewater treatment. Recently, metal-organic frameworks (MOFs) as an emerging precursor have been widely used for fabricating functional carbon materials. Herein, we reported ZIF-8 derived defect-rich nitrogen-doped carbon (ZCNs) via NaCl-assisted pyrolysis for efficient non-radical activation of peroxydisulfate to degrade rhodamine B (RB). All samples exhibited excellent catalytic activity, and ZCN-900 (pyrolyzed at 900 °C) was found to be the most active, able to degrade 96 % of RB quickly within 10 min. Quenching tests and electron paramagnetic resonance (EPR) analyses suggested that the singlet oxygen (¹O₂) dominated the degradation process by a non-radical pathway. Furthermore, the effect of anions and water quality on RB oxidation were investigated, and ZCN-900/PDS system showed great resistance to the anions and natural organic matters (NOM). This work may provide a significant addition to MOF-based functional materials for environmental remediation based on the results above.

Construction of highly durable electrocatalysts by pore-confinement and anchoring effect for oxygen reduction reaction

Developing highly stable and efficient catalysts towards the oxygen reduction reaction is important for the long-term operation in proton exchange membrane fuel cells. Herein, combined with the impregnation method, the...

Metal organic framework derived one-dimensional porous Fe/N-doped carbon nanofibers with enhanced catalytic performance

The aggregation of metal nanoparticles and collapse of precursor metal organic frameworks (MOFs) structure during the carbonization process largely hamper the catalytic performance of MOFs-derived carbon catalysts. Here, we report hollow and porous one-dimensional Fe/N-doped carbon nanofibers (Fe/NCNFs) for activating peroxymonosulfate (PMS), which was obtained by immobilizing Fe-MIL-101 on polyacrylonitrile (PAN) nanofibers via electrospinning technique followed by pyrolysis. The presence of one-dimensional PAN channel suppresses the agglomeration tendency of metal particles during the carbonisation process of Fe-MIL-101, resulting in a uniform dispersion of nanoparticles and an increase of catalytic active sites. The resultant Fe/NCNFs-9 possesses unique hierarchical architecture, large active surface area, well-dispersed Fe species, and abundant Fe-N active sites. These superiorities contributed to the better catalytic performance of Fe/NCNFs-9 compared with PAN derived carbon (PAN-C-9) and Fe-MIL-101 derived carbon (Fe-C-9). Through a series of inhibitor experiments and electrochemical tests, the radical pathway is dominant on BPA removal with the participation of the non-radical pathway in the multi-sites Fe/NCNFs-9/PMS/BPA system. Surprisingly, this strategy could successfully disperse Fe species and effectively reduce the Fe leaching. This work supplies a novel method to design efficient MOFs-derived carbon catalysts toward micropollutants removal.

Sponge Effect Boosting Oxygen Reduction Reaction at the Interfaces between Mullite SmMn2O5 and Nitrogen-Doped Reduced Graphene Oxide

Exploring the effect of interfacial structural properties on catalytic performance of hybrid materials is essential in rationally designing novel electrocatalysts with high stability and activity. Here, in situ growth of mullite SmMn₂O₅ on nitrogen-doped reduced graphene oxide (SMO@NrGO) is achieved for highly efficient oxygen reduction reaction (ORR). Combining X-ray photoelectron spectroscopy and density functional theory calculations, interfacial chemical interactions between Mn and substrates are verified. Interestingly, as revealed by charge density difference, the interfacial Mn-N(C) bonds display a sponge effect to store and compensate electrons to boost the ORR process. In addition, bidentate adsorption of oxygen intermediates instead of monodentate ones is observed in hybrid materials, which facilitates the interactions between intermediates and active sites. Experimentally, the hybrid catalyst SMO@NrGO exhibits a half-wave potential as high as 0.84 V, being comparable to benchmark Pt/C and higher than that of the pure SMO (0.68 V). The Zn-air battery assembled with SMO@NrGO shows a high discharge peak power density of 244 mW cm^-2 and superior cycling stability against noble metals.

Co(ii)Tetraphenyltetraphenanthroporphyrin@MWCNTs: enhanced π–π interaction for robust electrochemical catalysis

A cobalt(ii)tetraphenyltetraphenanthroporphyrin with phenanthrene-fused pyrrole rings was applied for robust HER and ORR.

Singlet oxygen-dominated non-radical oxidation process for efficient degradation of bisphenol A under high salinity condition

The degradation of organic contaminants under high salinity condition is still a challenge for environmental remediation due to the inhibiting effect resulted from the side reactions between radicals and anions. Here, we demonstrate the non-radical oxidation process via peroxymonosulfate (PMS) activation by metal-free carbon catalyst for efficiently decomposing bisphenol A (BPA) in saline water. The nitrogen-doped graphitic carbon (NGC700) exhibits excellent catalytic activity for depredating BPA at acid and neutral pH. Based on the scavenger experiments and electron paramagnetic resonance (EPR) analyses, the mechanism of catalytic oxidation was elucidated as the non-radical pathway, and singlet oxygen was identified as the primary reactive species. Experiments on the influence of anions (5-500 mM) further show that the inhibiting effect was overcame due to the non-radical process. Interestingly, Cl^- markedly facilitated the catalytic performance by generating HOCl in the catalytic process. The results highlight leveraging the non-radical pathway dominated by singlet oxygen to conquer the inhibitory effect of anions in NGC700/PMS system, which represents a crucial step towards environmental remediation under high salinity condition.

Magnetic solid-phase extraction for the removal of mercury from water with ternary hydrosulphonyl-based deep eutectic solvent modified magnetic graphene oxide

A novel ternary hydrosulphonyl-based deep eutectic solvent (THS-DES) comprised of choline chloride/itaconic acid/3-mercaptopropionic acid (molar ratio 2:1:1) was firstly synthesized. The composition, property and microscopic structure of the new magnetic adsorbent (THS-DES@M-GO) based on the THS-DES modified the magnetic graphene oxide (M-GO) was characterized by the system. Magnetic solid-phase extraction (MSPE) based THS-DES@M-GO was firstly researched for the removal of mercury (Hg²⁺) from water. Various influencing factors such as the mass of adsorbent, solution pH, initial Hg²⁺ concentration, the removal time and temperature had been systematically tested. Under optimized conditions the removal efficiency (R%) could achieved 99.91%. The precision, repeatability and stability experiments were investigated in detail to evaluate the presented method. The relative standard deviations (RSD) of the removal efficiency were 0.053%, 1.49% and 1.55%, respectively. The maximum adsorption capacity (Q_max) was 215.1 mg g^-1 and the data of the experiment fitted well with Langmuir model. Elution experimental studies shown that 94.94% of Hg²⁺ could be eluted by ethylenediaminetetraacetic acid (EDTA). After seven cycles of adsorption-desorption processes, the THS-DES@M-GO still retained a high removal efficiency of 90.23%. Compared with other adsorbents prepared in this work, THS-DES@M-GO displayed higher removal efficiency for Hg²⁺. Interference study proved the composites was tolerated and stabled under the complex matrix. What's more, the analysis of mercury contaminated water (from Guizhou, P.R., China) proved that the proposed method could be used to remove Hg²⁺ in practical application.