Iron(II) phthalocyanine covalently functionalized graphene as a highly efficient non-precious-metal catalyst for the oxygen reduction reaction in alkaline media

Morphological and structural design through hard-templating of PGM-free electrocatalysts for AEMFC applications

This study delves into the critical role of customized materials design and synthesis methods in influencing the performance of electrocatalysts for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). It introduces a novel approach to obtain platinum-free (PGM-free) electrocatalysts based on the controlled integration of iron active sites onto the surface of silica nanoparticles (NPs) by using nitrogen-based surface ligands. These NPs are used as hard templates to form tailored nanostructured electrocatalysts with an improved iron dispersion into the carbon matrix. By utilizing a wide array of analytical techniques including infrared and X-ray photoelectron spectroscopy techniques, X-ray diffraction and surface area measurements, this work provides insight into the physical parameters that are critical for ORR electrocatalysis with PGM-free electrocatalysts. The new catalysts showed a hierarchical structure containing a large portion of graphitic zones which contribute to the catalyst stability. They also had a high electrochemically active site density reaching 1.47 × 1019 sites g-1 for SAFe_M_P1AP2 and 1.14 × 1019 sites g-1 for SEFe_M_P1AP2, explaining the difference in performance in fuel cell measurements. These findings underscore the potential impact of a controlled materials design for advancing green energy applications.

Poly-Phthalocyanine-Doped Graphene Oxide Nanosheet Conjugates for Electrocatalytic Oxidation of Drug Residues

Donor and acceptor phthalocyanine molecules were copolymerized and linked to graphene oxide nanosheets through amidation to yield electrocatalytic platforms on glassy carbon electrodes. The platforms were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, UV/Vis spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The fabricated electrochemical catalytic surfaces were then evaluated toward electrocatalytic detection of ascorbic acid and tryptophan. These were characterized by a wide linear dynamic range and low limits of detection and quantification of 2.13 and 7.12 µM for ascorbic acid and 1.65 and 5.5 µM for tryptophan, respectively. The catalytic rate constant was 1.86 × 10⁴ and 1.51 × 10⁴ M⁻¹s⁻¹ for ascorbic acid and tryptophan, respectively. The Gibbs energy for catalytic reactions was −17.45 and −14.83 kJ mol⁻¹ depicting a spontaneous reaction on the electrode surface. The sensor platform showed an impressive recovery when applied in real samples such as fresh cow milk, in the range 91.71–106.73% for both samples. The developed sensor therefore shows high potential for applicability for minute quantities of the analytes in real biological samples.

Oxygen reduction reaction activity of an iron phthalocyanine/graphene oxide nanocomposite

Electrocatalysts with metal–nitrogen–carbon (M–N–C) sites have recently attracted much attention as potential catalysts for the oxygen reduction reaction (ORR), and a hybrid of iron phthalocyanine (FePc) and reduced graphene oxide (rGO) is one of the promising candidates. Herein, a FePc/GO nanocomposite was synthesized by electrostatic deposition on the electrode. The electrochemically reduced FePc/GO nanocomposite (ER(FePc/GO)) contained Fe²⁺ centers in well reduced graphene sites without agglomeration. The ER(FePc/GO) exhibited high ORR activity with an ORR onset (E_onset) and half-wave potential (E_1/2) of 0.97 and 0.86 V, respectively. Furthermore, the ORR activity successfully improved by adding an electrolyte such as KCl or KNO₃. The small H₂O₂ yield of 2%, superior tolerance to methanol addition and high-durability indicate that the ER(FePc/GO) is a promising electrocatalyst. Theoretical studies, indicating that the presence of Cl⁻ and NO₃⁻ ions lowered the conversion energy barrier, strongly supported the experimental results.

We demonstrate from both experimental and theoretical viewpoints that an iron phthalocyanine/graphene oxide nanocomposite directly synthesized on electrode exhibits high ORR activity.

Iron Phthalocyanine/Graphene Composites as Promising Electrocatalysts for the Oxygen Reduction Reaction

Recently, the development of non-precious electrocatalysts for the oxygen reduction reaction (ORR) has become important in replacing currently employed platinum (Pt)-based catalysts. Although Pt-based catalysts exhibit satisfactory ORR performances, their high price, easy methanol/CO2 poisoning, and poor long-term stability significantly hamper the forward movement of fuel cell technology. Among the various candidates, graphene-supported iron phthalocyanine (FePc) composites have attracted great attention because of their unique advantages, including low cost, good dimensional stability, high durability, and tunable catalytic activity. In the composite catalyst, FePc molecules are immobilized on graphene via noncovalent or covalent interactions. In addition, two-dimensional graphene substrates can improve not only the electrical conductivity of the composite, but also the dispersion of FePc molecules, triggering a significant improvement in the catalytic properties of the composite catalyst. Herein, we summarize the recent advances in FePc/graphene composite catalysts used for the ORR. Moreover, we discuss the challenges and future perspectives of this promising field.

Covalent structured catalytic materials containing single-atom metal sites with controllable spatial and chemical properties: concept and application

Keep your distance! A simple and effective protocol for connecting macrocycle polymers creates a new and versatile class of highly stable single-site catalytic materials.

Design and synthesis of CoIIHMTAA-14/16 macrocycles and their nano-composites for oxygen reduction electrocatalysis

The major concerns in the design of macrocycle based-ORR catalysts are: (i) understanding the macrocyclic, π-conjugation, central metal and substituent effects on ORR electrocatalysis; and (ii) the use of macrocycles on the electrode surface for the retention of ORR activity because of their poor stability. In this work, we demonstrated the aromaticity/π-electron conjugation effect on ORR activity by using the same macrocycles [HMTAA-14 and 16 (hexamethyltetraaza [14] and [16] annulenes)] with a difference in their macrocyclic cavity/π-electron conjugation. The macrocycles CoIIHMTAA-14 and CoIIHMTAA-16 and their nanocomposites with highly conductive carbon black were prepared by a microwave-assisted method and characterized by using multiple spectroscopy techniques. Comparative redox and oxygen reduction activity studies of CoIIHMTAA-14 and CoIIHMTAA-16 were undertaken by using cyclic voltammetry and linear sweep voltammetry in an alkaline medium. The composite CoIIHMTAA-16@C showed good ORR activity compared to CoIIHMTAA-14@C in O2-saturated KOH electrolyte. Since the CoIIHMTAA-14 and CoIIHMTAA-16 systems have a similar central atom and substituents, the shift of the ORR peak position in the +ive potential region for HMTAA-16 can be attributed to the difference in the size of the macrocyclic cavity (macrocyclic effect) and the extra stability of HMTAA-16 annulene due to its aromaticity.

Synergetic effects of graphene–CoPc/silk fibroin three-dimensional porous composites as catalysts for acid red G degradation

The disposal of dye wastewater is one of the hotspots of scientific research, and graphene–CoTAPc–SF composites exhibit more effective catalytic abilities.

Bioinspired Electrocatalysis of Oxygen Reduction Reaction in Fuel Cells Using Molecular Catalysts

One of the most important chemical reactions for renewable energy technologies such as fuel cells and metal-air batteries today is oxygen reduction. Due to the relatively sluggish reaction kinetics, catalysts are necessary to generate high power output. The most common catalyst for this reaction is platinum, but its scarcity and derived high price have raised the search for abundant nonprecious metal catalysts. Inspired from enzymatic processes which are known to catalyze oxygen reduction reaction efficiently, employing transition metal complexes as their catalytic centers, many are working on the development of bioinspired and biomimetic catalysts of this class. This research news article gives a glimpse of the recent progress on the development of bioinspired molecular catalyst for oxygen reduction, highlighting the importance of the molecular structure of the catalysts, from advancements in porphyrins and phthalocyanines to the most recent work on corroles, and 3D networks such as metal-organic frameworks and polymeric networks, all with nonpyrolyzed, well-defined molecular catalysts for oxygen reduction reaction.

Iron(III) phthalocyanine supported on a spongin scaffold as an advanced photocatalyst in a highly efficient removal process of halophenols and bisphenol A

This study investigated for the first time the degradation of phenol, chlorophenol, fluorophenol and bisphenol A (BPA) by the novel iron phthalocyanine/spongin hybrid material under various process conditions: hydrogen peroxide and UV irradiation. The heterogeneous catalyst, iron phthalocyanine/spongin (SFe), was produced by an adsorption process. The product obtained was investigated by a variety of spectroscopic techniques - X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and carbon-13 nuclear magnetic resonance (¹³C NMR) - as well as elemental and thermal analysis. The study confirmed the stable immobilization of the dye on the biopolymer. The results demonstrate that the degradation of phenols and BPA followed pseudo-second-order kinetics under different experimental conditions. The synergy of SFe, H₂O₂ and UV was found to produce a significant increase in the removal efficiency and resulted in complete removal of contaminants in a short time of 1 h. The reaction products were identified by high-performance liquid chromatography/mass spectrometry (HPLC-MS) and possible degradation pathways were proposed, featuring a series of steps including cleavage of CC bonds and oxidation.

Two-Dimensional N,S-Codoped Carbon/Co9S8 Catalysts Derived from Co(OH)2 Nanosheets for Oxygen Reduction Reaction

The development of highly active and cost-efficient electrocatalysts for the oxygen reduction reaction (ORR) is of great importance in a wide range of clean energy devices, including fuel cells and metal-air batteries. Herein, the simultaneous formation of Co₉S₈ and N,S-codoped carbon with high ORR catalytic activity was achieved in an efficient strategy with a dual templates system. First, Co(OH)₂ nanosheets and tetraethyl orthosilicate were utilized to direct the formation of two-dimensional carbon precursors, which were then dispersed into thiourea solution. After subsequent pyrolysis and template removal, N,S-codoped porous carbon-sheet-confined Co₉S₈ catalysts (Co₉S₈/NSC) were obtained. Owing to the morphological and compositional advantages as well as the synergistic effects, the resultant Co₉S₈/NSC catalysts with a modified doping level and pyrolysis degree exhibit superior ORR catalytic activity and long-term stability compared with the state-of-the-art Pt/C catalysts in alkaline media. Remarkably, the as-prepared carbon composites also reveal exceptional tolerance of methanol, indicating their potential applications in fuel cells.

Synthesis and characterization of graphene oxide supported cobalt (II) tetrasulfophthalocyanine as an efficient heterogeneous nanocatalyst for mercaptans oxidation from gasoline

In the present study, graphene oxide-supported cobalt (II) tetrasulfophthalocyanine (CoTsPc-GO) was synthesized using the incipient wetness impregnation assisted [Formula: see text]–[Formula: see text] assembling method. Applications for this material were investigated for ethyl mercaptan, [Formula: see text]-propyl mercaptan and [Formula: see text]-butyl mercaptan oxidation from fluid catalytic cracking (FCC) gasoline in a fixed bed reactor. The synthesized CoTsPc-GO catalysts were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy analysis, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDAX), thermogravimetric and differential thermal analysis (TGA-DTA), inductively coupled plasma optical emission spectroscopy (ICP-OES), and transmission electron microscopy (TEM). The effect of cobalt (II) tetrasulfophthalocyanine (CoTsPc) content (0–0.34 g), catalyst dosage (0.02–0.12 g) and temperature (30–40∘ C) on the performance of CoTsPc-GO catalysts were investigated during the Merox process. The stability and reusability of CoTsPc-GO catalyst for mercaptans oxidation were also tested. The obtained results revealed that the maximum mercaptan oxidation during the Merox process was obtained in CoTsPc-GO of 0.34 g, catalyst content of 0.1 g and a temperature of 40∘ C with ethyl mercaptan, [Formula: see text]-propyl mercaptan and [Formula: see text]-butyl mercaptan conversions of 99.9, 98.5 and 97.0%, respectively. The potential of CoTsPc-GO catalyst was investigated for further mercaptans oxidation. The results were compared to those obtained with an industrial impregnated active charcoal catalyst and a CoPc catalyst. The obtained results demonstrated the higher capability of CoTsPc-GO catalyst for mercaptans oxidation from FCC gasoline.

Fe9S10-decorated N, S co-doped graphene as a new and efficient electrocatalyst for oxygen reduction and oxygen evolution reactions

An advanced Fe₉S₁₀(700)/N,S-G catalyst for the oxygen reduction and evolution reactions was prepared via the combination of solvothermal and pyrolysis procedures.

Electrochemical oxygen reduction catalysed by Ni3(hexaiminotriphenylene)2

Control over the architectural and electronic properties of heterogeneous catalysts poses a major obstacle in the targeted design of active and stable non-platinum group metal electrocatalysts for the oxygen reduction reaction. Here we introduce Ni3(HITP)2 (HITP=2, 3, 6, 7, 10, 11-hexaiminotriphenylene) as an intrinsically conductive metal-organic framework which functions as a well-defined, tunable oxygen reduction electrocatalyst in alkaline solution. Ni3(HITP)2 exhibits oxygen reduction activity competitive with the most active non-platinum group metal electrocatalysts and stability during extended polarization. The square planar Ni-N4 sites are structurally reminiscent of the highly active and widely studied non-platinum group metal electrocatalysts containing M-N4 units. Ni3(HITP)2 and analogues thereof combine the high crystallinity of metal-organic frameworks, the physical durability and electrical conductivity of graphitic materials, and the diverse yet well-controlled synthetic accessibility of molecular species. Such properties may enable the targeted synthesis and systematic optimization of oxygen reduction electrocatalysts as components of fuel cells and electrolysers for renewable energy applications.

Electrochemical and spectroelectrochemical properties of thiadiazole substituted metallo-phthalocyanines

4-Thiadiazole substituted phthalonitrile and peripherally tetra-substituted phthalocyanine Cu(II), Fe(II) and Ti(IV)O complexes have been synthesized for the first time. Electrochemical properties of these complexes were determined with voltammetric and in situ spectroelectrochemical measurements. CuPc has redox inactive Cu(2+) center, therefore it gave three Pc based reduction and two Pc based oxidation processes. TiOPc and FePc complexes gave metal based redox processes in addition to Pc based redox reactions due to the redox activity of Ti(4+)O and Fe(2+) metal centers. Although FePc also gave three reduction and two oxidation reactions, peak potentials of these processes are different than those of CuPc due to the different assignments of the redox reactions. TiOPc went to five reduction and one oxidation reactions. Assignments of the redox processes were carried out with in situ spectroelectrochemical measurements. Spectra and color of the electrogenerated redox species of the complexes were also determined with in situ spectroelectrochemical and in situ electrocolorimetric measurements. Distinct color differences between the electrogenerated redox species were observed, which indicated their possible electrochromic usages.

Fabrication of functionalized 3D graphene with controllable micro/meso-pores as a superior electrocatalyst for enhanced oxygen reduction in both acidic and alkaline solutions

We have synthesized hierarchically 3D porous Fe₅C₂/N-doped graphene (3D Fe₅C₂/N-PG) with numerous micro/meso-pores by a controllable and facile strategy. The catalyst displays excellent catalytic activity for ORR in both acidic and alkaline media.

Systematic study of transition-metal (Fe, Co, Ni, Cu) phthalocyanines as electrocatalysts for oxygen reduction and their evaluation by DFT

A facile approach is reported to prepare a series of transition-metal phthalocyanines supported on graphitized carbon black (TMPc/GCB, TM: Fe, Co, Ni and Cu) as oxygen reduction reaction electrocatalysts,viaπ–π interaction self-assembly.

Calixarene-functionalized graphene oxide composites fixed on glassy carbon electrodes for electrochemical detection

Four composite materials were prepared by grafting calixarene derivatives onto the surfaces of graphene oxide (GO) via covalent functionalization to yield covalently functionalized graphene oxides (CFGOs).

Nitrogen and sulfur co-doped graphene aerogels as an efficient metal-free catalyst for oxygen reduction reaction in an alkaline solution

N–S-GAs 900 exhibit an interconnected porous 3D network with random orientation, crumpled sheets in SEM. The onset potential and limiting current density of N–S-GAs 900 are more positive and larger than other catalysts.

Synthesis of hybrid carbon spheres@nitrogen-doped graphene/carbon nanotubes and their oxygen reduction activity performance

The hybrid architecture of carbon spheres@nitrogen-doped graphene/carbon nanotubes (CS@N-G/CNT) was synthesized by a hydrothermal and ultrasonic-assisted method.

Spinel CoMn2O4 nanoparticles supported on a nitrogen and phosphorus dual doped graphene aerogel as efficient electrocatalysts for the oxygen reduction reaction

A novel strategy was developed for the preparation of a robust spinel CoMn₂O₄ nanoparticles supported on N, P-codoped GA catalyst with superior ORR activity, excellent stability and good tolerance of methanol crossover.