Pyrrolic Nitrogen Research Articles

Absorption Spectra of Protonated Corroles: Two Distinct Patterns Due to Peripheral Substitution Architecture

The origin of individual features in the ground state absorption spectra of two protonated corroles differing in the architecture of peripheral substitution (either Cm-aryl or Cb-alkyl) have been studied in detail with the ground state absorption spectroscopy and density functional theory calculations. The geometry optimization, molecular orbitals and absorption spectra calculation have been carried out. It was found that protonation leads to the saddle type macrocycle conformation in contrast with the wave type conformation known for the parent-free base corroles. The mean plane deviation parameter Δ23 for the macrocycle, pyrrole tilting angles and the degree of pyramidalization λ2 of all four pyrrole nitrogens was found to depend on the peripheral substitution architecture. Macrocycle conformation of the protonated forms has distinct asymmetrical features which are reflected by the sets of values of the tilting angles and values of pyramidalization degree. The pair of pyrroles B and C has smaller tilting angles and higher pyramidalization degree values, whereas the opposite trend was found for the pair of pyrroles A and D. Electronic effects and structural differences induced by substitution lead to the pronounced shifts of the molecular orbitals. In the Cb-alkylated corrole, almost-degenerated HOMO and HOMO-1 molecular orbitals lead to enhancement of the configuration interaction. As a result, the Qx transition oscillator strength goes down, becoming comparable to that of the Qy one. A large HOMO-HUMO-1gap in the Cm-aryl corrole minimizes the configuration interaction, giving rise to Qx band domination in the visible range spectrum.

Stable Dication Diradicals of Triply Fused Metallo Chlorin-Porphyrin Heterodimers: Impact of the Bridge on the Control of Spin Coupling to Reactivity.

We report an unexpected rearrangement, controlled by the nature of the bridge, leading to the formation of novel, remarkably stable triply fused dinickel(II)/dicopper(II) chlorin-porphyrin dication diradical heterodimers in excellent yields. Here, a dipyrromethene bridge gets completely fused between two porphyrin macrocycles with two new C-C and one C-N bonds. The two macrocycles exhibit extensive π-conjugation through the bridge, which results in an antiferromagnetic coupling between the two π-cation radicals. In addition, the macrocyclic distortion also favours a rare intramolecular ferromagnetic interaction between the CuII and π-cation radical spins to form a triplet state. The structural and electronic perturbation in the unconjugated dication diradical possibly enables the bridging pyrrolic nitrogen to undergo a nucleophilic attack at the nearby β-carbon of the porphyrin π-cation radical with a computed free energy barrier of >20 kcal mol-1 which was supplied in the form of reflux condition to initiate such a rearrangement process. UV-vis, EPR and ESI-MS spectroscopies were used to monitor the rearrangement process in situ in order to identify the key reactive intermediates leading to such an unusual transformation.

Surface Engineering of Multi-Walled Carbon Nanotubes via Ion-Beam Doping: Pyridinic and Pyrrolic Nitrogen Defect Formation

In this study, we present an innovative ion-beam doping technique for the controlled modification of the near-surface region of multi-walled carbon nanotubes (MWCNTs) aimed at creating pyridinic and pyrrolic nitrogen defects in their walls. This method involves the irradiation of MWCNTs with nitrogen ions using a high-dose ion implanter, resulting in the incorporation of nitrogen atoms into the nanotube structure. The structural and chemical changes induced by the ion-beam treatment were thoroughly characterized. Scanning electron microscopy (SEM) analysis revealed subtle changes in nanotube morphology, while X-ray diffraction (XRD) measurements exhibited altered peak intensities and a shift in the (002) reflection peak, indicating structural modifications, which correlates with transmission electron microscopy (TEM) data. X-ray photoelectron spectroscopy (XPS) analysis confirmed the successful embedding of nitrogen, mainly in pyridinic and pyrrolic configurations, as evidenced by the presence of corresponding lines in the N1s spectrum. Our findings demonstrate the feasibility of precisely engineering nitrogen defects in MWCNTs using the ion-beam doping technique. This approach is expected to be promising for the use of carbon nanotubes surface-functionalized with nitrogen atoms in the development of new devices for electronics, electrochemistry, catalysis, etc.

Improved electrochemical detection of copper ions in nitrogen doped ta-C films for marine corrosive monitoring

The corrosion of copper-based alloy in the harsh marine environment threatens the reliable operation and service life of marine engineering equipment. In this work, the nitrogen modified tetrahedral amorphous carbon (ta-C:N) film electrodes were prepared for marine-oriented copper ions detection. The relationship between structural evolution and electrochemical performance of ta-C:N film electrode tailored by N2 flux was evaluated. The sp2 cluster and the content of sp2-bonded carbon in ta-C:N film were promoted with the increase of N2 flux. XPS results indicated that the variation of N2 flux modified the nitrogen-containing groups of the ta-C:N film electrodes. The optimized ta-C:N film electrode deposited at N2 flux of 3 sccm showed a quasi-reversible electrode behaviors. Moreover, the ta-C:N film electrode exhibited a linear range from 8 × 10−3 mM to 5 mΜ, a detection limit of 8 × 10−3 mM, and good repeatability and reproducibility for Cu2+ detection in 3.5 wt% NaCl solution. The improved Cu2+ sensing properties were ascribed to the enhanced sp2 cluster and the introduction of multiple nitrogen-containing functional groups, especially the pyrrolic nitrogen and graphitic nitrogen. DFT computation and wavefunction analysis revealed that the pyrrolic nitrogen possessed the strongest interaction for copper ions among different nitrogen configurations.

Chalcogenopheno[3,2-b]pyrrole-Containing Donor-Acceptor-Donor Organic Semiconducting Small Molecules for Organic Field-Effect Transistors.

A group of chalcogenopheno[3,2-b]pyrroles, including thieno[3,2-b]pyrrole (TP), furo[3,2-b]pyrrole (FP), and selenopheno[3,2-b]pyrrole (SeP), and thieno[3,2-b]thiophene (TT) electron-donating units were coupled with a thiophene-flanked diketopyrrolo[3,4-c]pyrrole (ThDPP) acceptor to generate four donor-acceptor-donor (D-A-D) semiconducting small molecules (ThDPP-TT, ThDPP-FP, ThDPP-TP, and ThDPP-SeP). This study systematically investigated the differences between chalcogenopheno[3,2-b]pyrroles and TT. From the characterizations, chalcogenopheno[3,2-b]pyrrole-containing molecules showed lower band gaps and binding-energy cold crystallization behavior. The enthalpies of cold crystallization were correlated with the weight of the chalcogen in ThDPP-FP, ThDPP-TP, and ThDPP-SeP, which were evaluated as intermolecular chalcogen-bond interactions between chalcogen and pyrrole nitrogen in chalcogenopheno[3,2-b]pyrroles. A stronger chalcogen bond interaction resulted in stronger self-aggregation in thin films with thermal treatment, which resulted in a polycrystalline structure in chalcogenopheno[3,2-b]pyrrole-containing molecules. For the application in an organic field-effect transistor, all four molecules showed good performance with the highest hole mobilities as 6.33 × 10-3 cm2 V-1 s-1 for ThDPP-TT, 2.08 × 10-2 cm2 V-1 s-1 for ThDPP-FP, 1.87 × 10-2 cm2 V-1 s-1 for ThDPP-TP, and 6.32 × 10-3 cm2 V-1 s-1 for ThDPP-SeP, and the change of mobility is well correlated to the root-mean-square roughness of the thin films. Overall, all the chalcogenopheno[3,2-b]pyrrole-containing molecules showed lower band gaps, polymorphism, and better charge transport properties compared to TT-containing molecules, which motivates replacing TT with chalcogenopheno[3,2-b]pyrroles in conjugated polymers, non-fullerene small molecular acceptors, and narrow-band-gap donors.

Synthesis of N-alkoxycarbonyl Pyrroles from O-Substituted Carbamates: A Synthetically Enabling Pyrrole Protection Strategy.

The condensation of readily available O-substituted carbamates with 2,5-dimethoxytetrahydrofuran gives N-alkoxycarbonyl pyrroles in a single step and in good yield. By this method, several common amine protecting groups can be introduced on the pyrrole nitrogen. With the exception of N-Boc, N-alkoxycarbonyl groups have seen only minimal use for protection of the pyrrole nitrogen to date. Here, we show that N-alkoxycarbonyl protection can endow pyrrole with distinct reactivity in comparison with N-sulfonyl protection, for example, in a pyrrole acylation protocol employing carboxylic acids with a sulfonic acid anhydride activator.

Lignin-based iron single-atom nanozyme for detection of organophosphorus in soil

Organophosphorus pesticides (OPs) are widely used in agriculture and their residues can pose a threat to human health. Therefore the monitoring of their residue content is necessary. In this study, a colorimetric sensing strategy was designed to detect OPs by combining nanozymes with natural enzymes. Among them, iron single-atom nanozymes (Fe-N/C) were prepared by a one-pot synthesis method by pyrolyzing alkaline lignin. Various characterization tools were used to elucidate the microstructure and reaction mechanism of the nanozymes. N in the material is mainly bound to Fe in the form of pyrrole nitrogen, catalytic H2O2 will produce OH. Fe-N/C has good peroxidase-like activity and produces signals in UV detection upon the addition of 3,3′,5,5′-tetramethylbenzidine (TMB). Combining the catalytic properties of Fe-N/C and introducing acetylcholinesterase (AChE) for the detection of OPs in soil (take chlorpyrifos for example). The product of AChE catalyzed acetylcholine (ATCh) can inhibit the color signal. In contrast, the presence of chlorpyrifos destroys the activity of AChE and restores the reaction absorbance. The amount of chlorpyrifos can be calculated by observing the changes in color. The linear range of chlorpyrifos detection based on this strategy was 0.05–10.0 μg mL−1, the detection limit was 2.11 ng mL−1. This strategy provides a sensitive method for the quantitative determination of OPs, which is important for the monitoring of OPs in the environment.

Facile microwave assisted one-pot solid-state construction of Co-Fe spinel oxide/porous biochar for highly efficient 4-nitrophenol degradation: Effect of chemical blowing and surface vulcanization

Herein, microwave assisted one-pot solid-state construction method was developed for cellulose carbonization and Co-Fe spinel oxide loading to prepare Co-Fe spinel oxide/porous biochar for highly efficient 4-nitrophenol (4-NP) oxidation degradation through peroxymonosulfate (PMS) activation. With just 3 min domestic microwave heating of a solid mixture of cobalt nitrate, iron nitrate, α-cellulose, ammonium bicarbonate and thiourea, Co-Fe spinel and metal sulfides well dispersed, oxygen vacancies and pyrrole N enriched as well as BET increased porous Sx-CF@PC catalytic materials could be prepared with NH4HCO3 aided chemical blowing and thiourea assisted surface vulcanization. The optimal catalyst S1-CF@PC could achieve 99.0 % 4-NP removal in 10 min with rate constant as high as 0.564 min−1. Well dispersed spinel and metal sulfides could activate PMS to generate more SO4− and OH for 4-NP degradation; Meanwhile, oxygen vacancies and pyrrole nitrogen could promote 1O2 based non-free radical 4-NP degradation pathways. This study provided the simplest microwave assisted solid-state metal oxide/porous biochar construction for energetic organic pollutants degradation.

Divergent Diazo Approach toward Alkyl 5/4-Hydroxy-3H-benzo[e]indole-4/5-carboxylates.

A divergent diazo approach toward alkyl 5/4-hydroxy-3H-benzo[e]indole-4/5-carboxylates has been developed. The reaction of 1,3-diketones with alkyl 2-diazo-3-oxo-3-(2H-azirin-2-yl)propanoates catalyzed by Co(acac)3 or Ni(acac)2 gives various alkyl 3-(1H-pyrrol-2-yl)-2-diazo-3-oxopropanoate in good yields. The latter undergo Wolff rearrangement followed by the 6π-cyclization of transient ketene to form alkyl 5-hydroxy-3H-benzo[e]indole-4-carboxylates bearing various substituents in positions 1, 2, 7, and 8, as well as derivatives of methyl 4-hydroxy-6H-thieno[2,3-e]indole-5-carboxylates and methyl 5-hydroxy-7H-benzo[c]carbazole-6-carboxylate under thermolysis or Rh2(OAc)4 catalysis. Isomeric benzoindoles, alkyl 4-hydroxy-3H-benzo[e]indole-5-carboxylates, have been prepared by Boc-protection of the pyrrole nitrogen of alkyl 3-(1H-pyrrol-2-yl)-2-diazo-3-oxopropanoates followed by an intramolecular formal carbene insertion into the aromatic C-H bond catalyzed by Cu(OTf)2. The hydroxyl group of alkyl 5/4-hydroxy-3H-benzo[e]indole-4/5-carboxylates, through the formation of the corresponding triflates, allows the introduction of various substituents into the 5/4 position of benzo[e]indoles using the cross-coupling reaction and even form a new heterocyclic backbone, benzo[k]pyrrolo[2,3-i]phenanthridine, via a tandem Suzuki reaction/nucleophilic acyl substitution.

Regulatory effect of CaO on glutamate pyrolysis and NOx precursors formation

Pyrolysis is an effective method for safely disposing of sewage sludge via conversion into a usable energy source. However, municipal sludge has a high protein content, which is a major source of NOx precursors. This study investigated the effect of CaO on NOx precursor formation during glutamate pyrolysis and demonstrated that CaO occupies the carboxyl site of glutamic acid at 320 °C, which delays its decomposition and promotes the conversion of glutamic acid from a five- to a six-membered ring. At 400 °C, heterocyclic nitrogen in the tar peaked from 4.87 to 53.87% after adding CaO. As the temperature increases to 480 °C, CaO might promote the conversion of heterocyclic nitrogen into tricyclic piperazine dione in the tar, which subsequently decomposed to produce HCN in large quantities. At 480 °C, CaO contributed to the decrease in pyrrole, pyridine, and quaternary nitrogen in the semi-coke from 24.81%, 12.93%, and 7.43% to 1.91%, 5.97%, and 1.43%, respectively and promoted HCN hydrolysis to form NH3. At 480–680 °C, CaO interacted with NH3 to form CaCN2. The product of CaCxNy decomposition—CaCx—captured NH3. At high temperatures, CaO inhibited HCN release, which might be related to the reaction between CaO and HCN to form CaCxNy, subsequently reconverted into CaO at temperatures above 680 °C. These findings provide novel insights into the influence of CaO on amino acid pyrolysis to produce NOx precursors and the regulation of NOx precursor production.

N doping porous carbon embedded in self-assembled three-dimensional reduced graphene oxide networks for electrochemical hydrogen storage

Electrochemical hydrogen storage can realize reversible hydrogen absorption and desorption at room temperature and pressure, which has attracted extensive attention recently. A nanosheet-like reduced graphene oxide (rGO)-porous carbon composite with N-doping defect is prepared via a facile annealing, followed by hydrothermal and freeze-drying process. After N-doping, the porous carbon materials exhibit rich pore structure, and high pyridine nitrogen and pyrrolic nitrogen content. Adding them into the graphene self-assembly process, the aggregation tendency of graphene sheets can be reduced, the composite shows a free-standing 3D porous structure. Benefit from the synthetic effect between the rGO conductive network, the hierarchical porous structure, and the doping of N atoms, the rGO-N800 delivers a high hydrogen storage capacity of 266.3 mAh g−1 at 200 mA g−1 after 100 cycles. Moreover, the reversible capacities of the composite can reach 288.4, and 267.1 mAh g−1 at 1000 mA g−1 and 2000 mA g−1, respectively. The outstanding electrochemical performance of the composite demonstrates a promising direction for design carbon-based hydrogen storage materials.

Free-Base Corrole Anion.

Free-base corroles have long been known to be acidic, readily undergoing deprotonation by mild bases and in polar solvents. The conjugate base, however, has not been structurally characterized until now. Presented here is a first crystal structure of a free-base corrole anion, derived from tris(p-cyanophenyl)corrole, as the tetrabuylammonium salt. The low-temperature (100 K) structure reveals localized hydrogens on a pair of opposite pyrrole nitrogens. DFT calculations identify such a structure as the global minimum but also point to two cis tautomers only 4-7 kcal/mol above the ground state. In terms of free energy, however, the cis tautomers are above or essentially flush with the trans-to-cis barrier so the cis tautomers are unlikely to exist or be observed as true intermediates. Thus, the hydrogen bond within each dipyrrin unit on either side of the molecular pseudo-C2 axis through C10 (i.e., between pyrrole rings A and B or between C and D) qualifies as or closely approaches a low-barrier hydrogen bond. Proton migration across the pseudo-C2 axis entails much higher activation energies >20 kcal/mol, reflecting the relative rigidity of the molecule along the C1-C19 pyrrole-pyrrole linkage.

Oxide-mediated nitrogen doping of CVD graphene and their subsequent thermal stability.

Heteroatom doping of graphene is a promising approach for tailoring its chemical and electronic properties - a prerequisite for many applications such as sensing, catalysis, and energy storage. Doping chemical vapour deposition (CVD) graphene with nitrogen during growth (in-situ doping) is a common strategy, but it produces a distribution of inequivalent dopant sites and requires substantial modifications to the CVD growth process. In this study, we demonstrate a novel and simple oxide-mediated approach to introduce nitrogen dopants into pre-existing CVD graphene (ex-situ doping) which achieves comparable doping densities to in-situ doping methodologies. Furthermore, we demonstrate that thermal annealing of N-doped graphene can selectively remove pyridinic, retaining graphitic and pyrrolic nitrogen dopants, offering an attractive route to further modify graphene functionality. The methodologies we present are simple and scalable to precisely tailor graphene properties without the need to alter CVD growth protocols.

Efficient electro catalytic performance of palladium nanoparticles assisted on bi-composite material (GRNPs-GCN) for electro chemical oxidation of methanol in alkaline media

This study reports a novel co-deposited catalyst which covalently coupled composite of Pd@ GRNPs-GCN for methanol electro-oxidation was investigated. The prepared nanocomposite material was further characterized through FTIR, XRD, SEM, and EDX analysis. The results showed that the Pd@GRNPs-GCN has stronger interaction, active specific area & rich content of pyridine & pyrrole nitrogen species which promotes the dispersion of PdNPs on GRNPs-GCN to present superior catalytic efficiency towards MOR. Moreover, the electrochemical analysis of cyclic voltammetry (CV), chronoamperometry (CA) & electro chemical impedance spectroscopy (EIS) proved that fabricated Pd@GRNPs-GCN electro catalyst showed significant catalytic activity, lesser oxidation potential & longevity for the electrochemical oxidation of methanol in alkali media. All these results revealed that the nanocomposite hybrid electro catalyst for feature endeavours in DMFCs (Direct methanol fuel cells) applications.

Synthesis, Structure, Spectral, Electrochemical, and Theoretical Studies of Ru(II) Complexes of 3-Pyrrolyl BODIPY-Based Ligands.

3-Pyrrolyl BODIPY having an appended pyrrolyl group at the 3-position of BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) and its functionalized derivatives have been used as ligands to prepare one example of Ru(II) complex of pyrrolyl dipyrrin and three unique examples of bichromophoric BODIPY-Ru(II) complexes in good yields. The complexes were characterized by HR-MS, 1D and 2D NMR, X-ray analysis for two complexes, absorption, cyclic voltammetry, and DFT/TD-DFT techniques. The X-ray structure of the Ru(II) complex of pyrrolyl dipyrrin revealed that the geometry around the Ru(II) ion was pseudo-octahedral with an arene unit occupying three coordination sites in η6-fashion and two nitrogen atoms of the dipyrrin ring and one chloro group adopting the "three legs piano-stool" structure. The X-ray structure of the bichromophoric BODIPY-Ru(II) complex revealed that the BODIPY core was planar and the central B(III) was coordinated with two pyrrole nitrogens of the dipyrrin unit and two axial fluoride ions in a tetrahedral geometry, and Ru(II) was bonded to appended pyrrole "N" and "N" of benzimidazole substituent present at the α-position of appended pyrrole, one chloro group, and one arene ring in a pseudo-octahedral geometry. The spectral studies revealed that the electronic properties of the BODIPY unit in BODIPY-Ru(II) complexes were significantly altered, and electrochemical studies indicated that the BODIPY-Ru(II) complexes exhibit one oxidation corresponding to Ru(II) to Ru(III) and one reduction corresponding to the BODIPY unit. The DFT/TD-DFT studies corroborated the experimental observations.

Effect of 915‐MHz low‐temperature microwave irradiation on the molecular structure of coking coal

AbstractThe effect of microwave irradiation on the coking‐coal structure is important to study at the molecular scale to improve the quality of coking coal and optimize the coal‐blending technology for low‐quality coal. Through the characterization of coal structure by Fourier transform infrared spectrometer (FTIR), carbon‐13 nuclear magnetic resonance (13C‐NMR), and X‐ray photoelectron spectroscopy (XPS), the macromolecular structure unit model of coal before and after 915‐MHz microwave irradiation were constructed. A small number of alkyl side chains and cycloalkanes were broken, aromatic structures underwent condensation, and the aromatization of coal structure was increased after 915‐MHz microwave irradiation within 100–150°C. The content of hydroxyl self‐conjugated hydrogen bonds was increased, and the coal had more conjugated structures. Some phenolic hydroxyl groups and other functional groups were oxidized. The content of protonated pyridine and nitrogen oxides were increased, the content of pyridine and pyrrole nitrogen structures were decreased, and some nitrogen structures were oxidized. Mercaptan (thioether) and sulfoxide(sulfone) were partly converted into inorganic sulfur and partly converted into the more stable thiophene structure.

Nanofiber membrane coated with lithiophilic polydopamine for lithium metal batteries

Along with the cathode, anode, and liquid electrolyte in lithium-based secondary batteries, the separator is a crucial element for guaranteeing battery safety. However, conventional polyolefin separators suffer from inherent drawbacks such as inadequate compatibility with electrolytes and limited thermal stability. These limitations can lead to issues like high-temperature shrinkage, melting, and even combustion. Moreover, the vulnerability of separators toward lithium dendrite penetration exacerbates safety concerns associated with lithium-ion batteries. Hence, the design of high safety separators is currently a focus and challenge. In this study, we develop a multifunctional polymer-coupled nanofiber membrane by an electrospinning method that addresses the above issue as a separator of lithium metal battery. The nanofiber coating contains carbonyl oxygen, pyrrole nitrogen, and cross-linked networks with tertiary amine groups. These components effectively neutralize acidic compounds generated during the liquid electrolyte side reaction. X-ray micro-computed tomography analysis verifies the exceptional structural stability of the new separator, maintaining its 3D skeleton even after 2000 h of cycling. The nanofiber separator in a full Li||NCM811 cell achieves a high specific capacity of 136.6 mA h g−1 at 0.9 A g−1 and displays outstanding long-cycle stability over 500 cycles with a capacity retention of 88.5%.

Facilitating two-electron oxygen reduction with pyrrolic nitrogen sites for electrochemical hydrogen peroxide production

Electrocatalytic hydrogen peroxide (H2O2) production via the two-electron oxygen reduction reaction is a promising alternative to the energy-intensive and high-pollution anthraquinone oxidation process. However, developing advanced electrocatalysts with high H2O2 yield, selectivity, and durability is still challenging, because of the limited quantity and easy passivation of active sites on typical metal-containing catalysts, especially for the state-of-the-art single-atom ones. To address this, we report a graphene/mesoporous carbon composite for high-rate and high-efficiency 2e− oxygen reduction catalysis. The coordination of pyrrolic-N sites -modulates the adsorption configuration of the *OOH species to provide a kinetically favorable pathway for H2O2 production. Consequently, the H2O2 yield approaches 30 mol g−1 h−1 with a Faradaic efficiency of 80% and excellent durability, yielding a high H2O2 concentration of 7.2 g L−1. This strategy of manipulating the adsorption configuration of reactants with multiple non-metal active sites provides a strategy to design efficient and durable metal-free electrocatalyst for 2e− oxygen reduction.

Selective Electrocatalytic Oxidation of Nitrogen to Nitric Acid Using Manganese Phthalocyanine.

Ammonia is produced through the energy-intensive Haber-Bosch process, which undergoes catalytic oxidation for the production of commercial nitric acid by the senescent Ostwald process. The two energy-intensive industrial processes demand for process sustainability. Hence, single-step electrocatalysis offers a promising approach toward a more environmentally friendly solution. Herein, we report a 10-electron pathway associated one-step electrochemical dinitrogen oxidation reaction (N2OR) to nitric acid by manganese phthalocyanine (MnPc) hollow nano-structures under ambient conditions. The catalyst delivers a nitric acid yield of 513.2 μmol h-1 gcat-1 with 33.9% Faradaic efficiency @ 2.1 V versus reversible hydrogen electrode. The excellent N2OR performances are achieved due to the specific-selectivity, presence of greater number of exposed active sites, recyclability, and long period stability. The extended X-ray absorption fine structure confirms that Mn atoms are coordinated to the pyrrolic and pyridinic nitrogen via Mn-N4 coordination. Density functional theory-based theoretical calculations confirm that the Mn-N4 site of MnPc is the main active center for N2OR, which suppresses the oxygen evolution reaction. This work provides a new arena about the successful example of one step nitric acid production utilizing a Mn-N4 active site-based metal phthalocyanine electrocatalyst by dinitrogen oxidation for the development of a carbon-neutral sustainable society.

Highly efficient and photostable conversion of bicarbonate to acetate by a pyrrolic nitrogen enriched Ag3PO4/g-C3N4 photocathode with an intermediate band level in photo-assisted microbial electrosynthesis systems

A highly efficient and photostable acetate production from bicarbonate (HCO3−) reduction is demonstrated in a photo-assisted microbial electrosynthesis system (MES) using a pyrrolic nitrogen enriched Ag3PO4/g-C3N4 photocathode. Urea-treatment of the Ag3PO4/g-C3N4 photocathode synergistically improved the MES performance by up to 1.8 folds under visible light illumination, achieving acetate production of 9.6 mM/d with coulombic efficiency of 95%, negligible catalyst leaching, and solar-to-acetate efficiency of 1.15% over 12 days continuous operation. The photocorrosion of Ag3PO4 was efficiently inhibited by a two-step charge transfer process mediated by an intermediate band level introduced by oxygen-vacancies in the Ag3PO4 structure, which also facilitated light absorption and charge transfer through a Z-scheme mechanism, whereas the increased pyrrole N in the g-C3N4 provided supplementary active sites for direct and indirect (via H2) electron transfer to Serratia marcescens electrotroph. This study demonstrates the ingenious use of photocatalytic heterojunctions for achieving step-changes in the MES performance.