Pc Catalysts Research Articles

Computational design and screening of Single-Atom Phthalocyanine-Coordinated transition metal catalysts for the electrochemical cyanide reduction reaction

Catalysis facilitated by transition metals (TM), specifically when these are 4 N-coordinated and embedded within a phthalocyanine (Pc) framework, appears to have promising capabilities for the ecologically responsible generation of methane and ammonia, notably under conditions reflecting the ambient environment. The potential benefits of such applications have sparked escalating interest in studying single atom catalysts (SACs) with regard to their prospective role in the electrochemical cyanide reduction reaction (CNRR). Through the application of first-principles mechanistic investigations and electrochemical modeling, a variety of TM − Pc catalysts are examined under rigorous systematic exploration to ascertain their stability, activity and selectivity. To specifically address the scenarios, it's typically observed that the NC* model demands increased free energy inputs for CNRR, predominantly leading to the production of CH3NH2. In contrast, the analogous CN* model requires comparatively lower free energy, resulting in a more diversified mix of products, notably CH4 and NH3. Our research highlights the significant role of limiting potentials (UL) and their relationship with a particular kind of descriptor (φ) in crafting volcano plots, thereby elucidating the association between the inherent distinctive properties of various TM − Pc and their promising capabilities in CNRR activities. In a significant finding, the catalysts Sc − Pc, Ti − Pc, Cr − Pc and Fe − Pc are recognized as the most efficient electrocatalysts for CH4 and NH3 production through CNRR. This effectiveness is validated by their remarkable stability, superior reactivity, pronounced selectivity at relatively low limiting potentials (ranging from −0.05 to −0.39 V), and extraordinary Faradaic efficiencies exceeding 91.17 %.

Catalytic transfer hydrogenation of bio-oil over biochar-based CuO catalyst using methanol as hydrogen donor

The catalytic transfer hydrogenation (CTH) of bio-oil over CuO/PC (porous carbon) with the solid residue produced during biomass pyrolysis as the carrier was investigated with methanol as the hydrogen donor. The effect of carbonization temperature, activation temperature, KOH solution and metal loading on the physicochemical characteristics of CuO/PC catalystand catalytic transfer hydrogenation of bio-oil were investigated. The main alcohols formed in the CTH of bio-oil were 1, 4-butanediol, 1, 3-cyclopentadiol, 1, 3-cyclohexanediol, 2-cyclohexenol and alcohols. It was revealed that more alcohols were produced over CuO/PC using less Cu(NO3)2 than Cu2Al considering their favorable porous system. The well-developed pore structure is formed in PC at a higher calcination temperature and the concentration of activator, which was favorable for the CTH of bio-oil. Under the optimized preparation conditions, the mesopores accounting for 50% in the total pores, achieving the maximized yield of alcohols of 81%, and the well recycling performance was observed with the overall yield of alcohols decreases within 3% after five cycles because of the greater mesopores ratio. The biochar-based PC catalyst in this work enhances the effective usage of biomass to produce alcohols, fully conforming to the theme of energy conservation and low-carbon times.

Hierarchical macro-mesoporous electrocatalysts with dual-active sites of Ru single atoms and monodispersed Ru–Mo nanoclusters for efficient hydrogen evolution

Rationally designing high-performance electrocatalysts with high density and multiactive sites is an effective strategy to accelerate the alkaline hydrogen evolution reaction (HER) kinetics, yet it remains challenging. Herein, a catalyst comprising numerous Ru–Mo-based single atoms and subnanoclusters incorporated into a hierarchical macro-mesoporous carbon framework with a P-doped skeleton (Ru–Mo/PC) was successfully developed via a simple template-assisted pyrolysis method. Spherical aberration correction electron microscopy and X-ray absorption fine structure measurements revealed that the dual-active sites consisted of Ru–C5 single atoms and ultrasmall Ru–Mo nanoclusters (mean diameter of 0.94 nm). In particular, the as-constructed RuMo1.5/PC catalyst exhibited a high activity towards the HER, requiring an overpotential of only 17.9 mV at 10 mA/cm2, which outperformed a commercial Pt/C catalyst in alkaline media. Electrochemical performance results also indicated that introducing moderate Mo species played a crucial role in further boosting the HER activity compared to Ru/PC. The present work provides a step forward in designing efficient and stable catalysts with high-density, atomically dispersed active sites for hydrogen production.

(Digital Presentation) Electrocatalytic Cortisol Tracing Smart Patch

Rapid and continuous tracking of the stress hormone cortisol's circadian rhythm is vital for diagnosing diseases related to chronic stress and adrenal gland disorders [1]. Commercial cortisol sensors relying on labeled enzyme and antibodies suffer from limited stability, lengthy reaction time, and cross-reactivity with analogous molecules [2]. To address these issues, we developed an electrocatalytic sensor using phthalocyanine (Pc) doped molecularly imprinted polymer (MIP) modified screen-printed electrodes for label-free, reagentless, sensitive, and selective electrochemical detection of cortisol. The sensor was constructed via one-step electropolymerization of conductive prepolymer in the presence of Pc and template cortisol. The controlled release of cortisol templates resulted in an MIP network embedded with Pc catalysts in the vicinity of the cortisol-specific binding cavities. The sensor directly measures the cortisol level by catalysing the reduction reaction of the cortisol captured by the cavities of the MIP. Proof of studies was performed to detect cortisol over a wide concentration range varying from 500 pM to 10 µM with high selectivity against structurally similar hormones. The facile label-free and antibody-free cortisol sensor on a wearable smart patch offers an appealing approach for selective steroid hormone detection at point-of-care testing.

Assessment of Pretreatments for Highly Concentrated Leachate Waters to Enhance the Performance of Catalytic Wet Peroxide Oxidation with Sustainable Low-Cost Catalysts

Matured compost, derived from a mechanical and biological treatment (MBT) plant, was used as a precursor to produce catalysts through hydrothermal and thermal carbonization, HC and PC, respectively. HC and PC displayed suitable properties to act as catalysts in the catalytic wet peroxide oxidation (CWPO) treatment of the highly polluted leachate waters generated in the same MBT plant (TOC0 = 27 g L−1; COD0 = 60 g L−1; BOD5,0 = 23 g L−1). The influence of catalyst loading and pH were studied, considering multiple additions of H2O2. The best experimental conditions found were T = 80 °C, pH0 = 3.0, 7.2 g L−1 of HC catalyst, 85.7 g L−1 of H2O2, added in five batches in one-hour intervals between each addition. Under these experimental conditions, removals of 43%, 52%, 93%, 82%, 35%, 95% and 93% for the COD, TOC, BOD5, aromaticity, chlorides, turbidity and color number (CN) were, respectively, observed. Ion exchange resins and coagulation–flocculation were studied as pretreatment options to reduce the complexity of the leachate waters and enhance the CWPO results. Both strategies resulted in higher mineralization and enhanced the consumption efficiency of H2O2 (ηH2O2). The sequential treatment using coagulation–flocculation and CWPO with PC catalyst showed the best results, achieving abatement of 94%, 70%, 98%, 93%, 31%, 96% and 95% for COD, TOC, BOD5, aromaticity, chlorides, turbidity and CN, respectively.

Phthalocyanine pendented polyaniline via amide linkage for an electrochemical sensing of H2O2

Cobalt phthalocyanines are known to be the better electrocatalyst for a wide range of organic, inorganic, and biomolecular analytes. The synthesis of electrocatalysts through phthalocyanine (Pc) functionalization involves a single-step reaction to a multi-step reaction. The functionalization of Pc catalyst with the conducting polymer involves either simple electronic interactions or direct covalent bonding. Here we are reporting covalently connected tetra carboxy cobalt phthalocyanine (TCCoPc) pendent via amide linking to the conducting polyaniline (PANI) backbone. The synthesized electrocatalyst is extensively utilized for the sensing of biologically active H2O2 on the surface of the catalyst modified glassy carbon electrode (GCE). The synthesized molecule was characterized by various spectroscopic techniques and the detailed electrochemical activity of the synthesized molecule for the sensing of H2O2 was investigated using linear sweep voltammetry and chronoamperometry techniques, by fabricating on the GCE. The superlative catalytic activity of the synthesized molecule is might be due to the synergetic effect of pendanted macrocyclic Pc molecule with the redox-active demeanor of central cobalt metal atom and anchoring of the metal-centered Pc through amide linking with the conducting PANI.

Ammonium Nitrate‐Assisted Low‐Temperature Synthesis of Co, Co2P@CoP Embedded in Biomass‐Derived Carbons as Efficient Electrocatalysts for Hydrogen and Oxygen Evolution Reaction

AbstractElectrochemical water splitting into H2 and O2 provides a promising and sustainable strategy for the future production of clean energy. Herein, we report an ammonium nitrate (AN)‐assisted synthetic strategy to prepare Co, Co2P@CoP nanoparticles embedded in biomass‐derived porous carbons as bifunctional electrodes for water splitting. The use of AN is not only activating biomass to porous carbons, but also reducing the synthetic temperature significantly. The synergistic effects of the Co2P@CoP heterostructure could lead to a low adsorption energy of hydrogen (ΔGH*) and conduction band bending, together with the N/S‐codoped porous carbons could provide large specific surface area and desirable electron‐donating feature, contribute to the remarkable performance with overpotentials of 0.129 and 0.212 V for hydrogen evolution reaction (HER) in 0.5 mol L−1 H2SO4 and 1 mol L−1 KOH, and 0.328 V for oxygen evolution reaction (OER) in 1 mol L−1 KOH, at a current density of 10 mA cm−2. Moreover, the Co2P@CoP/PC catalysts enable overall water splitting with a small cell voltage of 1.63 V to achieve 10 mA cm−2 and exhibit long‐term durability over 1000 min.

Soybean straw biomass-derived Fe-N co-doped porous carbon as an efficient electrocatalyst for oxygen reduction in both alkaline and acidic media.

The development of highly efficient oxygen reduction reaction (ORR) catalysts is of great significance for the large-scale commercialization of fuel cells. In this work, honeycomb-like Fe–N co-doped porous carbon materials (Fe–N–PC) were prepared through a facile one-step pyrolysis strategy using soybean straw biomass as the precursor. The obtained Fe–N–PC catalyst exhibits excellent ORR performance with an onset potential of 0.989 V and a half-wave potential of 0.854 V in alkaline conditions, which positively shift only by 5 mV and 27 mV, respectively than those of the commercial Pt/C catalyst. Furthermore, the onset potential and the half-wave potential of the Fe–N–PC catalysts are up to 0.886 V and 0.754 V, respectively, under acidic conditions, which are superior to those of many other Fe, N-doped electrocatalysts. The ORR process can be regarded as a four-electron transfer process based on RRDE measurements. Moreover, the Fe–N–PC catalyst also shows greater stability and satisfactory methanol tolerance than the Pt/C catalyst. The superior electrocatalytic performance of Fe–N–PC may be attributed to the abundant nanoporous structure, large BET surface area, and Fe–N co-doping, which provide abundant and highly efficient active sites.

Pd nanoparticles anchoring to core-shell Fe3O4@SiO2-porous carbon catalysts for ammonia borane hydrolysis

A modified Stöber method is applied to synthesize the magnetic core-shell Fe3O4@SiO2 particles, followed by compositing a series of porous glucose-derived carbon with ZnCl2 as etchant. Then, ultrafine Pd nanoparticles (NPs) are successfully anchored to the resulting Fe3O4@SiO2-PC composites with an in-situ reduction strategy. The particle sizes of Pd NPs are mainly centered in the range of 2.3–4.3 nm in the as-prepared Pd/Fe3O4@SiO2-PC catalysts, owning a hierarchical porous structure with high specific surface area (SBET = 626.0 m2 g−1) and large pore volume (Vp = 0.61 cm3 g−1). Their catalytic behavior for the hydrogen generation from ammonia borane (AB) hydrolysis is investigated in details. The corresponding apparent activation energy is as low as 28.4 kJ mol−1 and the reaction orders with AB and Pd concentrations are near zero and 1.10 under the present conditions, respectively. In addition, the magnetic catalysts, which could be easily separated out by a magnet, are still highly active even after nine runs, revealing their excellent reusability.

Synergistic effect of metal-organic framework-derived boron and nitrogen heteroatom-doped three-dimensional porous carbons for precious-metal-free catalytic reduction of nitroarenes

We report a scalable and controllable synthesis of metal-organic framework (MOF)-derived three-dimensional boron and nitrogen heteroatom-doped porous carbons (3D-BNPCs) and their synergistic effect for metal-free catalytic 4-nitrophenol (4-NP) reduction. The substitution of boron atoms into zeolitic imidazole framework-8 (ZIF-8)-derived nitrogen-doped porous carbon (B-NPC-1200) significantly improves the electrical conductivity and the catalytic 4-NP reduction. We propose the heteroatom-doping of boron, nitrogen and oxygen in the 3D- B-N PC catalysts creates synergistic effect on 4-NP reduction by creating more catalytically active sites. High-Resolution X-ray Photoelectron Spectroscopy (HR-XPS) and Density Functional Theory (DFT) calculations were carried out to confirm and investigate the role of active sites on adsorption of 4-NP molecules in B-NPC-1200. We find that the strongly active sites can only be created based on the synergistic effect between nitrogen, boron and oxygen atoms, and the increased density of the active sites are responsible for the lowering of the apparent activation energy in B-NPC-1200 structure. As synthesized B-NPC-1200 exhibits superior catalytic activities for 4-NP reduction with a low apparent activation energy of 27.0 kJ/mol and a high reaction rate constant of 2.3*10^−3 (s-1). The catalyst can run five times without decreasing significant catalytic activity. The reduction reactions of various nitroarene compounds have been further tested using the B-N PC-1200 material as the precious-metal-free catalyst.

High Selectivity of Hydrogenation Reaction over Co0.15@C/PC Catalyst at Room Temperature.

In the field of catalysis, material scientists pay much attention to tuning the activity and chemoselectivity of metal nanoparticles. Herein, we design and successfully synthesize a series of Co NPs which show high performance on hydrogenation of nitroarenes with both activity and chemoselectivity. Co0.15@C/PC preferentially activates the -C═O bond over -NO2 in water with ammonia borane (AB); however, when the hydrogen source is changes to hydrazine hydrate (HH), the results are the opposite. The Co-based catalyst exhibits exceptionally high catalytic activity (with a TOF value of 10512 h-1, which is approximately 100 times than the akin catalysts) and chemo-selectivity for the hydrogenation of nitro compounds under mild conditions. Additionally, the catalyst can be separated easily by a magnet and shows prominent stabilit, which means that it can be reused for at least 10 cycles.

Theoretical Investigation of On-Purpose Propane Dehydrogenation over the Two-Dimensional Ru–Pc Framework

The on-purpose dehydrogenation of light alkanes has received considerable interest for producing olefins from abundant and cheap feedstock. The prevalent catalysts have been limited to Pt–Sn/Al2O3 and Cr2O3/Al2O3. In this work, we demonstrate by density functional theory that two-dimensional Ru–phthalocyanine (2D Ru–Pc) is a potential single-atom catalyst for selective alkene production via direct C–H bond activations. By analyzing the reaction pathways and the electronic structures of the transition states, we show that the catalytic origin of 2D Ru–Pc in C–H bond activations is the highly exposed d orbitals of the single Ru atom. The alkene selectivity can be attributed to the weak Ru−π binding interaction between the produced alkene and the 2D Ru–Pc catalyst. The distinct catalytic selectivity of such a 2D Ru–Pc catalyst may inspire further investigations of selective dehydrogenation of light alkanes on single-metal catalysts.

Probing Molecular-Scale Catalytic Interactions between Oxygen and Cobalt Phthalocyanine Using Tip-Enhanced Raman Spectroscopy.

Ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) is used to investigate adsorption of molecular oxygen (O2) on cobalt(II) phthalocyanine (CoPc) supported on Ag(111) single crystal surfaces, which is the initial step for the oxygen reduction reaction (ORR) using metal Pc catalysts. Two adsorption configurations are primarily observed, assigned as O2/CoPc/Ag(111) and O/CoPc/Ag(111) based on scanning tunneling microscopy (STM) imaging, TERS, isotopologue substitution, and density functional theory (DFT) calculations. Distinct vibrational features are observed for different adsorption configurations such as the 18O-18O stretching frequency at 1151 cm-1 for O2/CoPc/Ag(111), and Co-16O and Co-18O vibrational frequencies at 661 and 623 cm-1, respectively, for O/CoPc/Ag(111). DFT calculations show vibrational mode coupling of O-O and Co-O vibrations to the Pc ring, resulting in different symmetries of oxygen-related normal modes. This study establishes UHV-TERS as a chemically sensitive tool for probing catalytic systems at the molecular scale.

Solid Phase FePC Catalysts for Increased Stability of Oxygen Reduction Reaction Intermediates at the Cathode/Electrolyte Interface in Lithium Air Batteries

Solid-phase catalysts prepared by pyrolysis of Iron(II) phthalocyanine (FePC) embedded in high-surface carbons were evaluated for the catalysis of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Li+-conducting non-aqueous electrolytes. The ORR mechanism in high donor number (DN) dimethyl sulfoxide (DMSO)-based electrolytes is markedly different from that occurs in low DN acetonitrile(MeCN)-based electrolytes. The ORR is catalyzed by the reduced Fe(I) state of Fe(II)PC. Consequently, the Fe(II)PC/Fe(I)PC redox potential relative to O2 reduction potential in each electrolyte is important for ORR catalysis. In MeCN-based electrolytes, the Fe(I)PC catalyst is formed at a higher potential than the ORR potential. Hence the catalyzed ORR occurs at the inner-Helmholtz plane of the electrode, stabilizing the superoxide ion (O2−) formed by one-electron reduction of O2, as Fe(I)PC–O2−. Indeed, LiO2 was identified in the Raman spectra of cathodes from discharged Li-O2 battery cells. In DMSO-based electrolytes, the Fe(I)PC formation potential occurs below the ORR potential and accordingly LiO2 is more stable in its solvated state in the electrolyte solution as the Li(DMSO)n–O2− ion pair. This drives the ORR at the outer-Helmholtz plane of both catalyzed and uncatalyzed electrodes in DMSO-based electrolytes. The FePC embedded carbon electrode doubled the cycle life of Li-O2 cells utilizing low DN electrolytes.

Pt loaded onto silicon carbide/porous carbon hybrids as an electrocatalyst in the methanol oxidation reaction

Silicon carbide/porous carbon (SiC–PC) hybrids were directly synthesized via a facile evaporation-induced assembly approach combined with in situ carbothermal reduction in which soluble formaldehyde resin, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer and tetraethoxysilane were used as the source of carbon, the porogent and the source of silicon, respectively. The synthetic SiC–PC hybrid had a large specific surface area of 1163 m2 g−1 and the 10 nm SiC nanoparticles were well dispersed on the PC material. After loading with Pt nanoparticles, the resulting Pt/Si–PC catalyst had the highest reported unit mass electroactivity (836.93 A g−1 Pt) towards methanol electrooxidation (3.05 and 3.61 times the electroactivity of commercial PtRu/C and Pt/C catalysts). The Pt/SiC–PC catalyst also had a better stability than commercial PtRu/C and Pt/C catalysts. This enhanced electrocatalytic activity is attributed not only to the mutual effect of the hybrid support and the metal nanoparticles, but also to the large surface area that allows Pt to be used efficiently and gives the mass transportation required in a porous electrode. These results indicate that SiC–PC hybrids have great potential as high-performance catalyst supports for fuel cell electrocatalysts.

Enhancing heterogeneous catalytic activity of iron (II) phthalocyanine by ethanol and its application in 2,4-dichlorophenol detection

A chemical system for facile and accurate detection of 2,4-dichlorophenol (DCP) via iron (II) phthalocyanine (Fe(II)Pc) catalyzed chromogenic reaction is reported for the first time. In this system, DCP could be oxidized by dioxygen with the catalysis of Fe(II)Pc and then coupled with 4-aminoantipyrine (4-AAP) to generate pink antipyrilquinoneimine dye. Control experiments showed that the addition of ethanol could obviously enhance the catalytic activity of heterogeneous Fe(II)Pc catalysts because of the partial dissolution of Fe(II)Pc nanocubes, which was confirmed by the SEM analysis. On the basis of the detection results of DCP in the range from 2×10−5 to 9×10−4 mol/L, we obtained a regression equation (A = 0.187 5 + 0.01 209C (R 2=0.995 6)) with the detection limit (3σ) of 3.26×10−6 mol/L, which could be successfully used in detecting the real samples.

Photovoltaic and electrocatalytic properties of novel ball-type phthalocyanines bridged with four dicumarol

The new ball-type metallo bisphthalocyanines (Co(2)Pc(2) and Zn(2)Pc(2)) were synthesized from the corresponding [4,4'-bis(dicoumaroylphthalonitrile)] which can be obtained from the reaction of 3,3'-methylenebis(4-hydroxy-2H-chromen-2-one) and 4-nitrophthalonitrile. The structures of the newly synthesized compounds have been confirmed and characterized by elemental analysis, UV/Vis, IR and (1)H NMR spectroscopies and MALDI-TOF mass spectrometry. Solar cells of the configuration ITO/Co(2)Pc(2)/C60/Al and ITO/Zn(2)Pc(2)/C60/Al were fabricated. The effect of the thickness of the active Pc layer--the thickness of the Pc layer was varied from 15 to 80 nm--on solar cells parameters has been investigated. A nearly thickness independent open circuit voltage was observed in both structures. The maximum photovoltaic conversion efficiency, short circuit current and fill factor were observed in ITO/Zn(2)Pc(2)/C60/Al cell with 80 nm Pc layer to be 0.255%, 1 mA cm(-2) and 0.38, respectively. The redox properties of the ball-type complexes were investigated by cyclic voltammetry, controlled-potential coulometry and in situ spectroelectrochemistry in DMSO-TBAP. The electrochemical measurements showed that the complexes form ring-based and/or metal-based mixed-valence species, due to the remarkable intramolecular interactions between the two metal phthalocyanine units. The Vulcan XC-72(VC)/Nafion(Nf)/Co(2)Pc(2) modified glassy carbon electrode showed much higher catalytic performance towards oxygen reduction, compared to the VC/Nf/Zn(2)Pc(2) modified one. It was found that the VC/Nf/Co(2)Pc(2) catalyst is nearly insensitive to the presence of methanol. In the presence of 1 M methanol in the electrolyte, the catalytic performance of the Co(2)Pc(2)-based catalyst in oxygen reduction was much better than that of the Pt-based one. Thus, it was shown that the VC/Nf/Co(2)Pc(2) catalyst can be a good alternative to VC/Nf/Pt as a cathode catalyst in direct methanol fuel cells.

Formic Acid Oxidation on Composite Catalysts Made of Pt/C or Pd/C Impregnated with Phthalocyanines

The oxidation of formic acid at the surface of two families of composite catalysts, Pd/C–Pc and Pt/C–Pc, where Pc represents a phthalocyanine (–, Mn–, Fe–, Co–, Ni–, or CuPc), was studied in 10 mM HCOOH in 0.1 M electrolyte and in a fuel cell with 10 M HCOOH. For Pd/C–Pc catalysts; the impregnation of Pc onto Pd/C only resulted in lower mass activities compared to Pd/C alone. For Pt/C–Pc catalysts, the impregnation of CoPc, MnPc, or FePc onto Pt/C strongly enhanced the activity of the composite catalyst for formic acid oxidation at low potential ( vs reference hydrogen electrode) compared to Pt/C, whereas , NiPc, and CuPc had no influence. The most beneficial effect of Pc impregnation was obtained with CoPc impregnation onto Pt/C. Fuel cell testing was performed for Pd/C, Pd/C–CoPc, Pt/C, Pt/C–CoPc, and Pt–Ru/C. Similar with the results obtained in the solution, the best performing catalyst in fuel cell was Pd/C followed by Pd/C–CoPc, Pt/C–CoPc, Pt–Ru/C, and finally Pt/C. However, only Pt/C–CoPc and Pt–Ru/C were stable in fuel cell testing.

Simultaneous reduction of carbon dioxide and nitrate ions at gas-diffusion electrodes with various metallophthalocyanine catalysts

Electrochemical conversion of carbon dioxide with nitrate ions into useful material consisting of CN bond under the mild condition has attracted much attention. Simultaneous reduction of CO 2 and nitrate ions was investigated at gas-diffusion electrodes with various metallophthalocyanine (MPc, M: Ti, V, Cr, Mo, Fe, Ru, Co, Ni, Pd, Cu, Zn, Cd, Ga, In, Ge, Sn and Pb) catalysts. The current efficiencies of CO formation at CoPc and NiPc catalysts in the reduction of CO 2 alone are extremely higher than that at metal catalysts, hence these MPc catalysts were expected to have a fairly high ability for urea formation. However, since the reduction of nitrate ions to nitrite ions and ammonia does not occur at the MPc catalysts, urea is not formed in the simultaneous reduction of carbon dioxide and nitrate ions. For the urea formation, it was confirmed that simultaneous generation of ammonia- and CO-like precursors at the catalysts was necessary.

Electrochemical synthesis of urea at gas-diffusion electrodes: Part VI. Simultaneous reduction of carbon dioxide and nitrite ions with various metallophthalocyanine catalysts

Simultaneous reduction of carbon dioxide and nitrite ions was investigated at gas-diffusion electrodes with various metallophthalocyanine (M–Pc, M: Cr, Mo, Mn, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, In, Tl, Sn and Pb) catalysts. The formation of urea, CO, formic acid and ammonia at the gas-diffusion electrodes with Group 8–14 catalysts, except for Al and Ge, was found in the simultaneous reduction. The maximum current efficiency of urea formation is about 40% at −1.5 V on Ni–Pc catalysts. The formation of urea at the gas-diffusion electrodes with Group 4–7 catalysts was not found in the simultaneous reduction of CO 2 and nitrite. The ability for urea formation with the catalysts depends on the ability for CO and NH 3 formation. The catalysts with high ability for CO and NH 3 formation could form large amounts of CO-like and ammonia-like precursors.