Intrinsic Defect-Rich Graphene Coupled Cobalt Phthalocyanine for Robust Electrochemical Reduction of Carbon Dioxide

Hydrogenation of Covalent Organic Framework Induces Conjugated π Bonds and Electronic Topological Transition to Enhance Hydrogen Evolution Catalysis

Recently, many topological materials have been discovered as promising electrocatalysts in chemical conversion processes and energy storage. However, it remains unclear how the topological electronic states specifically modulate the catalytic reaction. Here, the two-dimensional metal phthalocyanine-based covalent organic framework (MPc-COF) is studied by ab initio thermodynamic calculations to clearly reveal the promotional effect on the electrochemical hydrogen evolution reaction (HER) induced by topological gapless bands (TGBs). We find that the prehydrogenated (and fluorinated) H4CdPc-COF(F) shows the best HER performance, with 0.016 V (near zero) overpotential. By tracking changes to the electronic structure and free energy as the prehydrogenation and HER processes occur, we are able to separately attribute the high HER efficiency in part due to the increase of the electron bath by donating electrons to the conjugated π bonds and also to the existence of TGBs. Specifically, the significant catalytic promotion by TGBs is proven to decrease the free energy by 0.218 eV to near zero. When the TGBs are destroyed, e.g., by replacing N with P and opening a band gap, the HER efficiency is reduced. This study opens avenues for deterministically harnessing topological band features to improve electrocatalysis.

Concentration-induced spontaneous polymerization of protic ionic liquids for efficient in situ adhesion

The advancement of contemporary adhesives is often limited by the balancing act between cohesion and interfacial adhesion strength. This study explores an approach to overcome this trade-off by utilizing the spontaneous polymerization of a protic ionic liquid-based monomer obtained through the neutralization of 2-acrylamide-2-methyl propane sulfonic acid and hydroxylamine. The initiator-free polymerization process is carried out through a gradual increase in monomer concentration in aqueous solutions caused by solvent evaporation upon heating, which results in the in-situ formation of a tough and thin adhesive layer with a highly entangled polymeric network and an intimate interface contact between the adhesive and substrate. The abundance of internal and external non-covalent interactions also contributes to both cohesion and interfacial adhesion. Consequently, the produced protic poly(ionic liquid)s exhibit considerable adhesion strength on a variety of substrates. This method also allows for the creation of advanced adhesive composites with electrical conductivity or visualized sensing functionality by incorporating commercially available fillers into the ionic liquid adhesive. This study provides a strategy for creating high-performance ionic liquid-based adhesives and highlights the importance of in-situ polymerization for constructing adhesive composites.

Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

Ionic liquids (ILs) have unique physicochemical properties that make them advantageous for catalysis, such as low vapor pressure, non-flammability, high thermal and chemical stabilities, and the ability to enhance the activity and stability of (bio)catalysts. ILs can improve the efficiency, selectivity, and sustainability of bio(transformations) by acting as activators of enzymes, selectively dissolving substrates and products, and reducing toxicity. They can also be recycled and reused multiple times without losing their effectiveness. ILs based on imidazolium cation are preferred for structural organization aspects, with a semiorganized layer surrounding the catalyst. ILs act as a container, providing a confined space that allows modulation of electronic and geometric effects, miscibility of reactants and products, and residence time of species. ILs can stabilize ionic and radical species and control the catalytic activity of dynamic processes. Supported IL phase (SILP) derivatives and polymeric ILs (PILs) are good options for molecular engineering of greener catalytic processes. The major factors governing metal, photo-, electro-, and biocatalysts in ILs are discussed in detail based on the vast literature available over the past two and a half decades. Catalytic reactions, ranging from hydrogenation and cross-coupling to oxidations, promoted by homogeneous and heterogeneous catalysts in both single and multiphase conditions, are extensively reviewed and discussed considering the knowledge accumulated until now.

Enhancing effect of cobalt phthalocyanine dispersion on electrocatalytic reduction of CO2 towards methanol

This paper focuses on enhancing the performance of electrocatalytic CO2 reduction reaction (CO2RR) by improving the dispersion of cobalt phthalocyanine (CoPc), especially for the methanol formation with multi-walled carbon nanotubes (CNTs) as a support. The promising CNTs-supported CoPc hybrid was prepared based on ball milling technique, and the surface morphology was characterized by means of those methods such as scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectra (XPS). Then, the synergistic effect of CNTs and ball milling on CO2RR performance was analyzed by those methods of cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), gas chromatography (GC), and proton nuclear magnetic resonance spectroscopy (1HNMR). Subsequently, the reduction mechanism of CO2 on ball-milled CoPc/CNTs was revealed based on the DFT calculations. The results showed that the electrocatalyst CoPc/CNTs hybrid prepared with sonication exhibited a conversion efficiency of CO2 above 60% at -1.0 V vs. RHE, accompanied by the Faradaic efficiencies of nearly 50% for CO and 10% for methanol, respectively. The addition of CNTs as the support improved the utilization efficiency of CoPc and reduced the transfer resistance of species and electrons. Then the ball-milling method further improved the dispersion of CoPc on CNTs, which resulted in the fact that the methanol efficiency was raised by 6% and partial current density was increased by nearly 433%. The better dispersion of CoPc on CNTs adjusted the reduction pathway of CO2 and resulted in the enhancement of methanol selectivity and catalytic activity of CO2. The probable pathway for methanol production was proposed as CO2 → *CO2- → *COOH → *CO → *CHO → *CH2O → *OCH3 → CH3OH. This suggests the significance of the ball-milling method during the preparation of better supported catalysts for CO2RR towards those high-valued products.

Amphiphilic Cobalt Phthalocyanine Boosts Carbon Dioxide Reduction

Due to the easy accessibility, chemical stability, and structural tunability of the macrocyclic skeleton, cobalt phthalocyanines immobilized on carbon supports offer an ideal research model for advanced electrochemical carbon dioxide reduction reaction (eCO2 RR). In this work, an amphiphilic cobalt phthalocyanine (TC-CoPc) is loaded on multiwalled carbon nanotubes to reveal the roles of hydrophilic/hydrophobic properties on catalytic efficiency. Surprisingly, the resultant electrode exhibits a CO Faradaic efficiency (FECO ) of 95% for CO2 RR with turnover frequency (TOF) of 29.4 s-1 at an overpotential of 0.585 V over long-term electrolysis in a H-type cell. In the membrane electrode assembly (MEA) device, the boosted transport of water vapor to the catalyst layer slows down carbonate crystallization and enhances the stability of the electrode, with FECO value of >99% over 27 h at -0.25 A, representing the best selectivity and stability among reported molecular catalysts in MEA devices. The amphiphilic cobalt phthalocyanine, which decreases interfacial charge and mass transfer resistance and maintains effective contact between active sites and the electrolyte, highlights the exceptional CO2 conversion from a molecular perspective.

A Novel Manner of Anchoring Cobalt Phthalocyanine on Edge-Defected Carbon for Highly Electrocatalytic CO2 Reduction

Cobalt phthalocyanine anchored on carbon material has attracted an enormous amount of attention due to its superior performance in electrocatalytic CO₂ reduction. However, the interaction between cobalt phthalocyanine and the carbon substrate remains problematic, and the role of intrinsic carbon defects is unfortunately ignored in the anchoring of cobalt phthalocyanine on carbon. Herein, new interactions between the bridging N atoms of cobalt phthalocyanine and the edge defects of carbon have been discovered, which result in a novel model of anchoring of cobalt phthalocyanine on ketjen black carbon. Such anchored cobalt phthalocyanine has been found to be responsible for superior catalysis for electrochemical reduction of CO₂ to CO with high selectivity and low overpotential.

Highly sensitive and selective serotonin (5-HT) electrochemical sensor based on ultrafine Fe3O4 nanoparticles anchored on carbon spheres

Neurotransmitter serotonin (5-HT) is involved in various physiological and pathological processes. Therefore, its highly sensitive and selective detection in human serum is of great significance for early diagnosis of disease. In this work, employing iron phthalocyanine as Fe source, ultrafine Fe₃O₄ nanoparticles anchored on carbon spheres (Fe₃O₄/CSs) have been prepared, which exhibits an excellent electrochemical sensing performance toward 5-HT. With carbonecous spheres turned into conductive carbon spheres under the heat treatment in N₂ atmosphere, iron phthalocyanine absorbed on their surfaces are simultaneously pyrolysised and oxidized, and finally transformed into ultrafine Fe₃O₄ nanoparticles. Electrochemical results demonstrate a high sensitivity (5.503 μA μM^-1) and a low detection limit (4 nM) toward 5-HT for as-prepared Fe₃O₄/CSs. In combination with the morphology and physicochemical property of Fe₃O₄/CSs, the enhanced sensing mechanism toward 5-HT is disscussed. In addition, the developed electrochemical sensor also displays a good sensing stability and an anti-interferent ability. Further applied in real human serum samples, a satisfactory recovery rate is achieved. Promisingly, the developed electrochemical sensor can be employed for the determination of 5-HT in actual samples.

Coupling Cobalt Phthalocyanine Molecules on 3D Nitrogen-Doped Vertical Graphene Arrays for Highly Efficient and Robust CO2 Electroreduction

Metallic phthalocyanines (MePcs) have shown their potential as catalysts for CO₂ reduction reactions (CO₂ RR). However, their low conductivity, easy agglomeration, and poor stability enslave the further progress of their CO₂ RR applications. Herein, an integrated heterogeneous molecular catalyst through anchoring CoPc molecules on 3D nitrogen-doped vertical graphene arrays (NVG) on carbon cloth (CC) is reported. The CoPc-NVG/CC electrodes exhibit superior performance for reducing CO₂ to CO with a Faradic efficiency of above 97.5% over a wide potential range (99% at an optimal potential), a very high turnover frequency of 35800 h^-1 , and decent stability. It is revealed that NVG interacts with CoPc to form highly efficient channels for electron transfer from NVG to CoPc, facilitating the Co(II)/Co(I) redox of CO₂ reduction. The strong coupling effect between NVG and CoPc molecules not only endows CoPc with high intrinsic activity for CO₂ RR, but also enhances the stability of electrocatalysts under high potentials. This work paves an efficient approach for developing high-performance heterogeneous catalysts by using rationally designed 3D integrated graphene arrays to host molecular metallic phthalocyanines so as to ameliorate their electronic structures and engineer stable active sites.

Heterogenised Molecular Catalysts for Sustainable Electrochemical CO2 Reduction

There has been a rapid rise in interest regarding the advantages of support materials to protect and immobilise molecular catalysts for the carbon dioxide reduction reaction (CO₂ RR) in order to overcome the weaknesses of many well-known catalysts in terms of their stability and selectivity. In this Review, the state of the art of different catalyst-support systems for the CO₂ RR is discussed with the intention of leading towards standard benchmarking for comparison of such systems across the most relevant supports and immobilisation strategies, taking into account these multiple pertinent metrics, and also enabling clearer consideration of the necessary steps for further progress. The most promising support systems are described, along with a final note on the need for developing more advanced experimental and computational techniques to aid the rational design principles that are prerequisite to prospective industrial upscaling.

Recent advances in electrocatalysis with phthalocyanines

Applications of phthalocyanines (Pcs) in electrocatalysis-including the oxygen reduction reaction (ORR), the carbon dioxide reduction reaction (CO₂RR), the oxygen evolution reaction (OER), and the hydrogen evolution reaction (HER)-have attracted considerable attention recently. Pcs and their derivatives are more attractive than many other macrocycles as electrocatalysts since, although they are structurally related to natural porphyrin complexes, they offer the advantages of low cost, facile synthesis and good chemical stability. Moreover, their high tailorability and structural diversity mean Pcs have great potential for application in electrochemical devices. Here we review the structure and composition of Pcs, methods of synthesis of Pcs and their analogues, as well as applications of Pc-based heterogeneous electrocatalysts. Optimization strategies for Pc-based materials for electrocatalysis of ORR, CO₂RR, OER and HER are proposed, based on the mechanisms of the different electrochemical reactions. We also discuss the structure/composition-catalytic activity relationships for different Pc materials and Pc-based electrocatalysts in order to identify future practical applications. Finally, future opportunities and challenges in the use of molecular Pcs and Pc derivatives as electrocatalysts are discussed.