Nitride Catalysts Research Articles

Novel carbon nitride for efficient degradation of organic pollutants and value-added recycled plastics: synergistic effects of nitrogen vacancies and Fe

The introduction of nitrogen vacancies (VN) and iron (Fe) single atoms sites significantly enhances the visible light absorption and charge transfer ability of carbon nitride (CN) catalysts. This paper presents the successful synthesis of a VN-rich, Fe single atoms incorporated CN, a catalyst that demonstrates exceptional degradation performance and cycling stability. The 2-mercaptobenzothiazole (MBT) removal rate by 20Fe-CN reached 99.51% within just 11min under visible light, and the catalyst maintained superior photocatalytic performance upon repeated use. Additionally, the 20Fe-CN/Photo/High-temperature system effectively converted polystyrene (PS) to benzoic acid (BA), achieving a BA yield of 19.73% after 48hours. Under visible light irradiation, the VN sites captured electrons and facilitated their rapid transfer to neighboring Fe sites, enhancing the photocatalytic redox processes. This study also identified ·O2- as the primary active species in the photocatalytic process. This research supports the development of diverse single-atom modified carbon nitride photocatalysts, holding significant potential for wastewater treatment and plastic resource recycling, and providing valuable insights for future photocatalysts in environmental remediation.

Visible light activation of permanganate by nitrogen vacancy-modified g-C3N4: Insight into the role of photo-generated electrons and holes

The photo-activation of permanganate (PM) for pollutant degradation in water has garnered significant interest due to its potential, yet it is impeded by efficiency constraints. In this study, the nitrogen-vacancy (NV) engineered graphitic carbon nitride (CN) catalysts with high light absorption, well photocarrier separation, and robust photoreduction capability were employed to activate PM under visible light irradiation (Vis) for sulfadiazine degradation. A high first-order rate constant of 0.185 min−1 was observed with the Vis/PM/NV-modified CN system, which was 25.2 and 7.1 times greater than those from Vis/PM and Vis/PM/CN system respectively. More interestingly, it was found that PM predominantly engaged with photo-generated holes as Lewis acid sites, elevating its oxidation potential and concurrently stimulating the production of photo-generated electrons. Meanwhile, dissolved oxygen (DO) was reduced by photo-generated electrons to form superoxide ions, singlet oxygen, and hydroxyl radicals. These produced reactive species through the synergistic activation of PM and DO, finally participated in the degradation of pollutants. Furthermore, the versatility and reusability of NV-CN catalysts were assessed under different reaction conditions, demonstrating promising prospects for practical applications. The results will contribute to a comprehensive understanding of the mechanism of photoactivation of PM for pollutant degradation.

In situ ammonium formation mediates efficient hydrogen production from natural seawater splitting

Seawater electrolysis using renewable electricity offers an attractive route to sustainable hydrogen production, but the sluggish electrode kinetics and poor durability are two major challenges. We report a molybdenum nitride (Mo2N) catalyst for the hydrogen evolution reaction with activity comparable to commercial platinum on carbon (Pt/C) catalyst in natural seawater. The catalyst operates more than 1000 hours of continuous testing at 100 mA cm−2 without degradation, whereas massive precipitate (mainly magnesium hydroxide) forms on the Pt/C counterpart after 36 hours of operation at 10 mA cm−2. Our investigation reveals that ammonium groups generate in situ at the catalyst surface, which not only improve the connectivity of hydrogen-bond networks but also suppress the local pH increase, enabling the enhanced performances. Moreover, a zero-gap membrane flow electrolyser assembled by this catalyst exhibits a current density of 1 A cm−2 at 1.87 V and 60 oC in simulated seawater and runs steadily over 900 hours.

Photoinduced Deoxygenative C2 Arylation of Quinoline N-oxides with Phenylhydrazines to 2-Arylquinolines over Porous Tubular Graphitic Carbon Nitride Semiconductor Photocatalyst.

The photo-induced deoxygenative C2 arylation of quinoline N-oxides to 2-arylquinolines is achieved over a heterogeneous porous tubular graphitic carbon nitride (PTCN) catalyst with phenylhydrazines as arylation reagent. A wide range of quinoline N-oxides can be efficiently transformed into their corresponding 2-arylquinolines under visible light irradiation. Moreover, PTCN catalyst is easily separated and could be reused several times without loss to its original activity.

Self-assembly of decavanadate and Ni(HCO3)2 into nanoparticles anchored on carbon nitride for efficient photocatalytic Minisci-type alkylation

Photocatalysis Minisci-type reactions involving carbon-centered radicals (CCRs) have emerged as a hot and significant topic in the field of organic synthesis chemistry. Herein, we present a nickel-vanadium nanoparticle anchored on carbon nitride catalyst (NiV-CN) and persulfate as a hydrogen atom transfer (HAT) precursor. This catalyst enables the photocatalytic Minisci-type CCR alkylation. The nickel-vanadium nanoparticles are synthesized via electrostatic attraction between [V10O28]6− anions and Ni(HCO3)2, with in situ self-assembly occurring during the hydrothermal process. In the model reaction of 4-methylquinoline with cyclohexane, the NiV-CN catalyst showed high stability, without significant loss its catalytic activity after three cycles. The CCRs was extended to cycloalkanes, adamantanes, and cyclic ethers, which react with quinoline, isoquinoline, and benzothiazole to provide the corresponding products in moderate to excellent yields. Mechanism studies indicate that nickel-vanadium nanoparticles play a crucial role in the formation process of carbon-centered radicals by activating the persulfate precursor into sulfate radicals under visible-light irradiation.

Achieving Highly Durable Intermetallic PtMn3N Electrocatalyst via the Strong Metal‐N Bonds toward Oxygen Reduction Reaction

AbstractPt‐based intermetallic compounds have been considered promising electrocatalysts in the practical applications of fuel cells; however, the development of Pt‐based catalysts that meet performance targets of high activity, maximized stability, and low cost remains a huge challenge. Herein, an atomically ordered and low‐Pt intermetallic nitride (PtMn3N) catalyst are synthesized consisting of a strained Pt shell and PtMn3N core on carbon support via the KCl‐matrix protection strategy. The PtMn3N catalyst represents a high mass activity of 0.70 A mgPt−1 at 0.9 V and a specific activity degradation of 4.2% after 5000 potential cycles for the oxygen reduction reaction (ORR) in rotating disk electrode (RDE) testing, which substantially outperformed commercial Pt/C (0.25 A mgPt−1 and 17.4%). Density functional theory calculations reveal that the introduction of Mn elements to the Pt lattice is beneficial to produce appropriate compressive strain to weaken the binding energy of oxygen species and the introduction of N elements to promote the strong metal‐N interactions is conducive to alleviating the dissolution of metal atoms, allowing for displaying the prominent durability. This work provides an effective strategy of N‐doped Pt‐based intermetallic compounds to enhance the corrosion resistance of 3d transition metals and to enhance the ORR performance.

Enhanced coking resistance of alumina-supported cobalt nitride catalyst via doping of phosphorus for dry reforming of methane

A novel P-doped Co4N/γ-Al2O3 catalyst was firstly designed for dry reforming of methane (DRM). It was found that the use of P doping Co4N/γ-Al2O3 can enhance its coking resistance, which might be due to a decrease in CH4 dissociation ability and an increase in CO2 dissociation ability, as well as the increase of cobalt species capable of interacting with alumina.

BiW11/Porous carbon nitride catalyst improves charge carrier separation efficiency for enhanced photocatalytic hydrogen evolution

Solar water splitting has received tremendous attention as hydrogen emerges as a promising energy carrier. Carbon nitride (CN) is an ideal candidate for H2 evolution via water splitting on account of its unique optical and electrical properties. To mitigate photoexcited charge carriers recombination that has severely limited the photocatalytic activity of CN, a heterojunction photocatalyst of CN with monovacant bismuth tungstate (Na6[BiW11O38H]·22H2O, noted as BiW11) as a highly efficient photocatalyst is designed. Herein, the porous carbon nitride (PCN) is first fabricated via the gas template method, and then PCN with BiW11 is modified via the impregnation method. Series of BiW11-based PCN composites with different BiW11 loadings (BiW11/PCN-x, x represents the amount of BiW11) are created to merge complementary advantages of both materials. Visible-light-driven photocatalytic properties of BiW11/PCN-x composites have been examined with Na2S/Na2SO3 sacrificial agents. The hydrogen evolution rate of the BiW11/PCN-10 is 2.45 and 1.98 times than that of PCN and BiW11. This extraordinary photocatalytic activity is ascribed to increased attachment sites for catalysts and active centers for hydrogen reduction due to porous structure and significantly facilitated charge separation efficiency through the type-II heterostructure. The resulting composites would be a potential candidate strategy for the design of highly efficient polyoxomatalate-based photocatalysts for efficient hydrogen production applications.

Highly active manganese nitride-europium nitride catalyst for ammonia synthesis

The development of efficient catalysts for ammonia synthesis under mild conditions is critical for establishing a carbon-neutral society powered by renewable ammonia. While significant effort has been focused on Fe and Ru-based catalysts, there have been very limited studies on manganese-based catalysts for ammonia synthesis because of their low intrinsic catalytic activity. Herein, we report that the synergy between manganese nitride (Mn4N) and europium nitride (EuN) yields an ammonia synthesis rate that is 41 and 25 times higher than that of neat Mn4N and EuN, respectively. Detailed studies suggest that a [Eu-N-Mn] species at the interface of Mn4N and EuN plays a pivotal role in ammonia synthesis. Compositing of Mn4N with other rare earth metal nitrides such as LaN, PrN, and CeN also leads to a significant enhancement in catalytic activity. This work broadens the scope of advanced nitride catalysts for ammonia synthesis.

Enhancing solar-driven overall water splitting via both sacrifice and noble metal free photocatalysis: copper cluster/boron-doped carbon nitride catalysts

Enhancing solar-driven overall water splitting via both sacrifice and noble metal free photocatalysis: copper cluster/boron-doped carbon nitride catalysts

MnS doping regulating Co active sites on fibrous cobalt nitride as bifunctional oxygen electrocatalyst for high-performance Zn-air battery

Aiming to achieve high-efficiency bifunctional catalysts, doping engineering is applied to construct bifunctional catalysts for oxygen electrodes in Zn-air batteries to strengthen the catalytic kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, MnS doped cobalt nitride catalyst (MnS/CoNx) with divergent fiber morphology is prepared by low temperature nitriding for the self-assembling layered double hydroxides (LDH). The MnS/CoNx shows excellent electrical conductivity and improved catalytic activity on ORR and OER with low overpotential of 290 mV at 10 mA cm−2 and a good half-wave potential of 0.80 V in ORR compared with CoNx and MnO/CoNx. The contribution of the increased bifunctional catalytic performance is possible from the more active center Co3+ and Mn4+, and the elevated electron transport resulted from the opportune high conductive MnS doping. The MnS/CoNx catalyst-driven Zn-air battery achieves a higher power density of 228 mW cm−2 and the excellent long-term stability of 500 h at 20 mA cm−2 far surpassing the commercial Pt/C+RuO2 catalyst.

A bioinspired Fe/Mo bimetallic nitride catalyst for efficient electrochemical ammonia synthesis and Zn-nitrate battery

The electrocatalytic nitrate reduction reaction to ammonia (NRA) offers a promising alternative to traditional ammonia synthesis methods. In nature, enzymes containing molybdenum and iron sites catalyze the reduction of nitrate and nitrite ions. Drawing inspiration from these enzymes, we synthesized a carbon-coated nano-octahedra of FeMo-based nitride (FeMoN@C NO) by pyrolyzing phosphomolybdic acid hydrate (POM) doped Fe-NH2-MIL-101 to catalyze NRA. Experimental results demonstrate that in an alkaline environment, FeMoN@C NO exhibits a suitable hydrogen evolution reaction (HER) capacity, and the protons or hydroxyls produced effectively facilitate the hydrogenation reaction in the ammonia synthesis process. Additionally, the introduction of Mo increases the number of active sites and effectively reduces the thermodynamic barrier in NRA, thereby enhancing the rate of ammonia synthesis. As a result, FeMoN@C NO displays outstanding NH3 Faradaic efficiency (FE) of 98.2 % and an NH3 yield of 434.16 µmol/h cm−2. Building upon the excellent electrocatalytic properties of FeMoN@C NO, a new Zn-nitrate battery system is assembled in this work, which exhibits an outstanding peak power density of 3.23 mW cm−2 and an FE of 91.58 % for NH3 production. This work provides a new perspective for designing enzyme-mimicking nitrate reduction catalysts and broadens the application of Zn-based batteries.

Eco-friendly and large-scale fabrication of NiMoN/Ni(OH)2/NF as highly efficient and stable alkaline hydrogen evolution reaction electrode

Bimetallic nickel-molybdenum nitride (NiMoN) catalysts have attracted great attention due to their remarkable similarity to group VIII noble metals in terms of electronic structure, good electron conductivity, and durability for the hydrogen evolution reaction (HER). However, the existing approaches for fabricating NiMoN catalysts usually entail a series of multiple steps and hazardous ammoniated ingredient. As a result, these methods are difficult to be scaled up for large-area fabrication towards industrial water splitting. Herein, a hierarchical composite NiMoN@Ni(OH)2@NF composite electrode with a sheet morphology was synthesized based on a rational combination of seawater etching and magnetron sputtering. This method is easily scalable for producing large-area electrodes with minimal pollution. The incorporation of Ni(OH)2@NF nanoarray carriers enhances the exposure of additional active sites on the NiMoN layer, thereby augmenting the electrochemically active specific surface area of the electrode.The as-synthesized NiMoN@Ni(OH)2@NF electrode demonstrates excellent HER activity, with an overpotential of 57 mV at 10 mA cm−2, and exhibits remarkable long-term catalytic stability for over 100 h at a current density of 100 mA cm−2.This study presents an eco-friendly and straightforward method for preparing large-scale transition metal nitride catalysts with high catalytic activity.

Contact-electro-catalytic CO2 reduction from ambient air

Traditional catalytic techniques often encounter obstacles in the search for sustainable solutions for converting CO2 into value-added products because of their high energy consumption and expensive catalysts. Here, we introduce a contact-electro-catalysis approach for CO2 reduction reaction, achieving a CO Faradaic efficiency of 96.24%. The contact-electro-catalysis is driven by a triboelectric nanogenerator consisting of electrospun polyvinylidene fluoride loaded with single Cu atoms-anchored polymeric carbon nitride (Cu-PCN) catalysts and quaternized cellulose nanofibers (CNF). Mechanistic investigation reveals that the single Cu atoms on Cu-PCN can effectively enrich electrons during contact electrification, facilitating electron transfer upon their contact with CO2 adsorbed on quaternized CNF. Furthermore, the strong adsorption of CO2 on quaternized CNF allows efficient CO2 capture at low concentrations, thus enabling the CO2 reduction reaction in the ambient air. Compared to the state-of-the-art air-based CO2 reduction technologies, contact-electro-catalysis achieves a superior CO yield of 33 μmol g−1 h−1. This technique provides a solution for reducing airborne CO2 emissions while advancing chemical sustainability strategy.

Photoinduced Ordered Growth of Copper-Doped Polyaniline Nanotubes: A Method to Improve the Catalytic Activity for C-N Coupling Reactions.

Polyaniline-supported metal nanoparticles (M@PANIs) have been widely employed as catalysts for organic reactions. Traditionally, the catalytic activities of the materials can be improved by introducing functional groups onto the aniline monomers, but it may enhance the catalyst cost and reduce the production yield of the material. This work reports a new strategy for improving the catalytic activity of M@PANIs. It was found that induced by visible light in the presence of a polymeric carbon nitride catalyst and copper dopant, the oxidative polymerization of simple aniline occurred slowly and orderly to produce the copper-doped polyaniline nanotubes. The unique tubular structure protected the catalytically active Cu(I) inside and endowed even more sufficient contact of the catalytic sites with reactants so that the material exhibited excellent catalytic performances in C-N coupling reactions.

Synthesis of polymeric 2D-graphitic carbon nitride (g-C3N4) nanosheets for sustainable photodegradation of organic pollutants

A superficial, one step thermal polycondensation method has been employed for the manifestation of graphene like graphitic carbon nitride (g-C3N4) catalyst. The as synthesized g-C3N4 was well characterized by SEM and EDAX analysis, XRD, ATR-IR, FTIR, Fluorescence spectroscopy, Raman spectroscopy and UV–Visible spectroscopy which provide structural, morphological assemblage relating to the structure of g-C3N4. The g-C3N4 showed that an outstanding photochemical stability, morphology, conductive carbon framework and superior photocatalytic activity. The band gap value of g-C3N4 is 2.34 eV determined using Tauc plot. Due to low band gap (2.33 eV) and unique morphology which provides high separation and migration ability of the photogenerated charges, the g-C3N4 shows enhanced photocatalytic activity for the removal of many organic dyes such as Rhodamine B (RhB), Crystal Violet (CV), Methylene Blue (MB), Methyl Orange (MO), Naphthol Orange (NO) and a phenol derivative, p-Nitrophenol (p-NP). Among them, RhB dye was degraded almost 81 % at 90 min under sunlight irradiation in presence g-C3N4 while other dyes and p-NP was degraded at lower rate. From the experimental data, it was found that MO and p-NP degradation rate was least. The rate constant for degradation of Rh B is 1.1 × 10−2 min−1. Therefore, g-C3N4 can be used as an efficient photocatalyst for waste water treatment by the removal of such organic pollutants.

Ru–modified graphitic carbon nitride for the solar light–driven photocatalytic H2O2 synthesis

Hydrogen peroxide (H2O2) is an efficient and environmentally friendly oxidant as well as a promising energy-carrier alternative to hydrogen. Its solar light-driven photocatalytic synthesis from H2O and O2 is a high-prospect sustainable alternative to the industrial anthraquinone process. Hybrid Ru-modified graphitic carbon nitride (g-C3N4) catalysts were prepared by thermal polymerisation of melamine/Ru(III) acetylacetonate mixtures, and subsequent thermal exfoliation. Simultaneous Ru incorporation and thermal exfoliation impacted the morphology and the structure of the g-C3N4 sheets, and low-atomicity Ru species with small nanoclusters and single atoms were observed only in the Ru-modified exfoliated g-C3N4 photocatalysts. We demonstrated the potential of a joint thermal exfoliation and modification with Ru to enhance the H2O2 synthesis efficiency of the g-C3N4 photocatalyst under simulated sunlight. A volcano-type behavior was observed with increasing the Ru content, and the best performance was obtained for exfoliated g-C3N4 with an ultra-low Ru content of 0.019 wt.%, that outperformed both its bulk counterpart and the pristine exfoliated reference in terms of initial H2O2 synthesis rate and H2O2 formation rate constant. The enhanced performance was attributed to the presence of highly dispersed low atomicity Ru as well as to more accessible active sites and carrier migration channels. Quenching experiments revealed a mixed reactional pathway involving both two-step one-electron and one-step two-electron O2 reduction in the photocatalytic H2O2 production.

Microwave-Mediated ammonia synthesis over Co2Mo3N catalysts at low pressures

The Haber-Bosch process for ammonia (NH3) synthesis is a major contributor to greenhouse gas emissions and is responsible for > 2 % of the world’s energy consumption each year encouraging the need for alternative renewable-based options. This study investigates an earth-abundant ternary metal nitride (i.e., Co2Mo3N) catalyst to develop a renewable-based NH3 synthesis approach, utilizing an energy-efficient microwave-assisted route. Using a combination of spectroscopic and catalytic measurements coupled with surface analysis techniques, Co2Mo3N was evaluated as a stable and efficient NH3 synthesis catalyst. Results presented here demonstrate NH3 synthesis on Co2Mo3N at ∼420 ℃ and ambient pressure yield ∼0.7 mmolNH3.gcat-1.h−1 and up to ∼12 mmolNH3.gcat-1.h−1 at 28 bar under microwave irradiation. Co2Mo3N displayed an activation energy of ∼72 kJ.mol−1 and yielded NH3 following first-order kinetics with respect to both H2 and N2. These studies illustrate the potential of using this catalyst for a sustainable, cost-effective, and environmentally friendly approach to producing NH3.

Microwave-assisted ammonia decomposition over metal nitride catalysts at low temperatures

The negative environmental impact of fossil fuel-based energy systems has unveiled the need to develop a COx-free sustainable hydrogen (H2) economy. Employing a microwave-assisted route, a ternary metal nitride catalyst (i.e., Co2Mo3N), and a low-temperature-pressure NH3 decomposition process, this study investigated the possibility of developing a distributed H2 production process. This study not only explored lower cost-based catalyst systems but also the use of a microwave reactor to increase the energy efficiency of the process. Results from catalytic NH3 decomposition experiments, performed in microwave reactors on Co2Mo3N catalyst, demonstrated the peak energy efficiency (of ∼0.006 kgH2/kWh) at 400 °C in ambient pressure (with an NH3 conversion >90%) which was around ninety times (∼90 x) more efficient than a conventional system. Activation energy calculation also displayed a 20% less energy requirement for the microwave-based process (∼31 kJ mol−1) than the conventional system (∼37 kJ mol−1), indicating the advantage of the microwave-based process. Further microwave-assisted catalytic measurements and characterization of the Co2Mo3N catalyst, using x-ray diffraction (XRD) technique and scanning electron microscopic (SEM) images, revealed the excellent stability of this material at its peak performance (at 400 °C) and illustrated the potential of using this catalyst for a sustainable, economic, and energy-efficient approach for producing COx-free H2.

Metal-Support Interaction in Pt Nanodisk-Carbon Nitride Catalyst: Insight from Theory and Experiment.

Metal-support interaction plays a critical role in determining the eventual catalytic activity of metals loaded on supporting substrates. This interaction can sometimes cause a significant drop in the metallic property of the loaded metal and, hence, a drop in catalytic activity in the reactions, especially in those for which low charge carrier transfer resistance is a necessary parameter. Therefore, there should be a case-by-case experimental or theoretical (or both) in-depth investigation to understand the role of support on each metal. Here, onto a layered porous carbon nitride (g-CN), we grew single crystalline Pt nanodisks (Pt@g-CN) with a lateral average size of 21 nm, followed by various characterisations such as electron microscopy techniques, and the measurement of electrocatalytic activity in the O2 reduction reaction (ORR). We found that intercalating Pt nanodisks in the g-CN interlayers causes an increase in electrocatalytic activity. We investigated the bonding mechanism between carbon support and platinum using density functional theory and applied the d-band theory to understand the catalytic performance. Analysis of Pt's density of states and electronic population across layers sheds light on the catalytic behaviour of Pt nanoparticles, particularly in relation to their thickness and proximity to the g-CN support interface. Our simulation reveals an optimum thickness of ~11 Å, under which the catalytic performance deteriorates.