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Anion‐exchange membrane fuel cells provide the possibility to use platinum group metal‐free catalysts, but the anodic hydrogen oxidation reaction (HOR) suffers from sluggish kinetics and its source is still debated. Here, over nickel‐tungsten (Ni−W) alloy catalysts, we show that the Ni : W ratio greatly governs the HOR performance in alkaline electrolyte. Experimental and theoretical studies unravel that alloying with W can tune the unpaired electrons in Ni, tailoring the potential of zero charge and the catalytic surface to favor hydroxyl adsorption (OHad). The OHad species coordinately interact with potassium (K+) ions, which break the K+ solvation sheath to leave free water molecules, yielding an improved connectivity of hydrogen‐bond networks. Consequently, the optimal Ni17W3 alloy exhibits alkaline HOR activity superior to the state‐of‐the‐art platinum on carbon (Pt/C) catalyst and operates steadily with negligible decay after 10,000 cycles. Our findings offer new understandings of alloyed HOR catalysts and will guide rational design of next‐generation catalysts for fuel cells. [ABSTRACT FROM AUTHOR]

The expensiveness of oxygen reduction reaction (ORR) catalyst materials especially Pt has hindered the commercialization of next-generation energy conversion devices including metal–air batteries and polymer electrolyte membrane fuel cells. Fe– N –C has drawn attention as a nonprecious metal catalyst owing to its high but commercially unsatisfactory ORR performance; nevertheless, additional heteroatom co-doping could help augment its ORR activity. Here we report nitrogen/fluorine-coordinated iron-co-doped carbon (Fe@NFC) catalysts with improved ORR performance in alkaline media. The annealing temperature affects the nitrogen/fluorine doping and functional group formation, as ascertained by an analysis of control samples annealed at various temperatures. To assess the synergy between the doped fluorine and nitrogen-coordinated iron, we compare the catalyst annealed at 700 °C (Fe@NFC700) with control samples containing different heteroatom dopants but annealed at 700 °C (Fe@NC, Fe@FC). Fe@NFC700 shows improved ORR kinetics and onset potential than those of Fe@NC and commercial Pt/C, respectively, in alkaline media. • The most optimal annealing temperature of the Fe@NFC is found at 700 °C for the ORR. • F-doping increases the ORR favorable N -functional group ratio like Fe-N x. • The high ECSA from N -functional groups enhances the ORR performance. • F-functional groups like semi-ionic C –F bonds provide remarkable ORR kinetics. • The Fe@NFC700 catalyst exhibits higher onset potential than Pt/C in 0.1 M KOH. [ABSTRACT FROM AUTHOR]

Hydrogen energy has the advantages of high energy density,green and sustainability,which make it an ideal energy source for human society.Hydrogen generation by seawater electrocatalysis becomes the strategic direction of hydrogen energy industry in the future.The activity and stability of cathode hydrogen evolution catalyst are vital to this hydrogen energy strategy.Although the precious metal Pt-based electrocatalysts have shown excellent catalytic performance on hydrogen evolution,the high price and scarce resources limit their large-scale application.Therefore,nonprecious metal electrocatalysts have attracted much research attention.Starting from the principle of hydrogen evolution reaction,important parameters of overpotential,Tafel slope,Faraday efficiency,specific activity and mass activity,etc.were introduced to evaluate catalytic performances.The review summarized recent progress on multiple nonprecious metal electrocatalysts for cathode hydrogen generation by seawater electrocatalysis,and the problems of current research was clarified.Additionally,the future research of nonprecious metal electrocatalysts in cathode for large-scale hydrogen generation by seawater electrocatalysis was prospected from the following aspects:1) Designing nonprecious metal catalysts with high activity and stability;2) Optimizing production and preparation process of nonprecious metal catalyst;3) Using advanced test and characterization to construct reaction models;4) Deepening theoretical calculation for the mechanism research.

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The regioselective C–H arylation of substituted polycyclic aromatic hydrocarbons (PAHs) is a desired but challenging task. A copper-catalyzed C7–H arylation of 1-naphthamides has been developed by using aryliodonium salts as arylating reagents. This protocol does not need to use precious metal catalysts and tolerates wide variety of functional groups. Under standard conditions, the remote C–H arylation of other PAHs including phenanthrene-9-carboxamide, pyrene-1-carboxamide and fluoranthene-3-carboxamide has also accomplished, which provides an opportunity for the development of diverse organic optoelectronic materials.

Non-platinum carbon-based catalysts have attracted much more attention in recent years because of their low cost and outstanding performance, and are regarded as one of the most promising alternatives to precious metal catalysts. Activated carbon (AC), which has a large specific surface area (SSA), can be used as a carrier or carbon source at the same time. In this work, stable pine peel bio-based materials were used to prepare large-surface-area activated carbon and then compound with cobalt phthalocyanine (CoPc) to obtain a high-performance cobalt/nitrogen/carbon (Co-N-C) catalyst. High catalytic activity is related to increasing the number of Co particles on the large-specific-area activated carbon, which are related with the immersing effect of CoPc into the AC and the rational decomposed temperature of the CoPc ring. The synergy with N promoting the exposure of CoNx active sites is also important. The Eonset of the catalyst treated with a composite proportion of AC and CoPc of 1 to 2 at 800 °C (AC@CoPc-800-1-2) is 1.006 V, higher than the Pt/C (20 wt%) catalyst. Apart from this, compared with other AC/CoPc series catalysts and Pt/C (20 wt%) catalyst, the stability of AC/CoPc-800-1-2 is 87.8% in 0.1 M KOH after 20,000 s testing. Considering the performance and price of the catalyst in a practical application, these composite catalysts combining biomass carbon materials with phthalocyanine series could be widely used in the area of catalysts and energy storage.

Transition metal‐nitrogen‐carbon (M−N−C) materials have received extensive attention as promising catalysts for oxygen reduction reaction (ORR). The surface morphology and the pore structure of the carbon supports have important effects on the ORR activity. Herein, metal‐organic complexes were prepared via a simple NaOH‐mediated method by the organometallic reaction of Fe3+/Co2+ ions and benzimidazole in the presence of polyvinylpyrrolidone. Metal‐organic complexes with either cuboid or cylindrical morphologies were obtained by modulating the initial ratio of Fe3+/Co2+. FeCo containing N‐doped carbon catalysts (FexCoy−N−C) decorated with FexCoy nanoparticles were then fabricated by a direct carbonization of the metal‐organic complexes. FexCoy−N−C catalysts have hierarchical micro‐/mesoporous structure and retain the morphologies of microcuboids and microcylinders of the metal‐organic complexes precursors. The Fe1Co7−N−C exhibits promising catalytic activity with an onset potential of 0.967 V, a half‐wave potential of 0.816 V, and a limiting current density of 4.86 mA cm−2 in 0.1 M KOH. The ORR catalytic activity should be attributed to the FeCo−Nx active sites and the encapsulated FeCo alloy nanoparticles activating the surrounding N‐doped carbon layers. [ABSTRACT FROM AUTHOR]

The development of non‐precious metal catalysts toward oxygen reduction reaction (ORR) is essential for widespread application of fuel cells. Herein, bimetallic Cu−Zn co‐doped porous N/C catalysts (Cu−Zn−N/C) with high N content were synthesized via a simple metal‐organic framework (MOF)‐derived method. The as‐prepared Cu−Zn−N/C catalyst presents superior catalytic activity toward ORR with an onset potential of 0.90 V, a half‐wave potential of 0.79 V, and a diffusion limiting current density of 5.82 mA cm−2. It is found that Cu exists in three forms: one exists in Cu particles, and the others exist in Cu single atoms (either in high valence or in zero valence) that embedded in the carbon substrate. The evaporation of Zn atoms during the pyrolysis induces the pore structure of the carbon matrix, making it possible to support for the zero valent Cu atoms. In addition, as an efficient Cu‐based catalyst for many applications, we show that the as‐prepared catalyst can selectively oxidize 1,2‐propanediol to lactic acid with 75.7 % selectivity at 82.8 % conversion. [ABSTRACT FROM AUTHOR]

Non-precious metal doped carbonaceous materials are currently the most promising alternative towards oxygen reduction reaction (ORR) electrocatalysts in terms of cost, accessibility, efficiency and durability. In this work, a simple one-step pyrolysis process was used for the synthesis of copper doped graphitic carbon nitride (Cu-g-C 3 N 4) as electrocatalyst. The as-synthesized Cu-g-C 3 N 4 material is displaying excellent electrocatalytic response towards ORR in alkaline medium. In comparison to commercial Pt/C catalyst, Cu-g-C 3 N 4 exhibits high methanol tolerance, long term stability, without compromising (4e−) electron transfer pathway process and attaining less than 4% H 2 O 2 formation. The enhanced electrocatalytic behaviour may be ascribed to the formation of active sites strongly coupled into the nitrogen-rich carbon matrix. Such a low-cost, extremely durable and stable electrocatalyst can therefore be regarded as an efficient cathodic material, which can be utilized for several renewable energy conversion technologies such as fuel cell, biofuel cell and metal-air battery. [ABSTRACT FROM AUTHOR]

Summary: The application of nonprecious metal catalysts, such as iron (Fe) and cobalt (Co) catalyst, to direct liquid fuel cells (DLFCs), especially in direct methanol fuel cells, has been widely investigated. However, the application of such non‐Pt catalysts as cathode catalysts in direct formic acid fuel cell (DFAFC) operations has not yet been investigated. This study intends to evaluate the formic acid tolerance of such catalysts in case of oxygen reduction reaction. In addition, we investigate their performances in DFAFC using the Fe‐ and Co‐nitrogen‐doped carbon nanotubes (Fe‐NCNT and Co‐NCNT) as the cathode catalysts and compare these performances with the commercial Pt/C catalyst. Herein, Fe‐NCNT and Co‐NCNT were synthesized using the conventional method by the pyrolysis of the multiwalled carbon nanotubes, dicyandiamide, and metal salt under the flow of N2 at 800°C. Both the Fe‐NCNT and Co‐NCNT catalysts exhibit higher formic acid tolerance when compared with that exhibited by the Pt/C catalyst. Further, single‐cell tests with hydrogen‐fed polymer electrolyte fuel cell (PEFC) and DFAFC operations were conducted under various operating conditions to compare the performances of the cells while using the prepared catalysts and the conventional Pt/C catalyst. The PEFC performances in both the Fe‐NCNT and Co‐NCNT catalysts were significantly low (94.9mW cm−2 for Fe‐NCNT and 164.0 mW cm−2 for Co‐NCNT at 60°C). Regardless, the Co‐NCNT catalyst exhibited a maximum power density of 160.7 mW cm−2 in DFAFC operated at 60°C and7‐M formic acid. This value is comparable with that for DFAFC with a Pt/C catalyst (128.9mW cm−2) and is considerably higher than that obtained for other DLFCs while using a non‐Pt catalyst. Therefore, the usage of a non‐Pt metal catalyst as the cathode catalyst is preferable in case of DFAFC. [ABSTRACT FROM AUTHOR]

In this study, a rapid, scalable, and cost-effective method was developed for synthesizing cobalt–iron metal oxide catalysts for water electrolysis. Cobalt-iron metal oxide catalysts were synthesized using the microwave-assisted hydrothermal methods by varying the molar ratios of cobalt and iron. When the cobalt to iron ratio was 2:1, its electrolytic cell yielded the onset potential of only 1.56 V at 10 mA cm−2, which is close to the thermodynamically reversible potential. When its cell potential was at 1.8 V, the cell current density was approximately 130 mA cm−2. The results of the stability test showed a steady-state cell current density of 130 mA cm−2 and remained constant for more than 16 h at a continuous cell potential of 1.8 V. Compared with other catalysts, cobalt–iron metal oxide catalysts showed lower overpotential and lower Tafel slope than did conventional precious metal catalysts such as PtO 2 and IrO 2. Cobalt-iron metal oxide catalysts serve as an inexpensive route to large-scale commercialization through facile synthesis for enhanced electrochemical water splitting. Image 1 • Co 2 Fe 1 was synthesized by microwave assisted hydrothermal method. • Electrochemical activity of Co 2 Fe 1 for OER was studied. • Amorphous nature and particle size of Co 2 Fe 1. • Co 2 Fe 1 attains lower overpotential of 1.56 V for 10 mAcm−2 and 47.36 mV dec−1. • Co 2 Fe 1 was stable in 1 M KOH at 130 mAcm−2 for more than 16 h. [ABSTRACT FROM AUTHOR]

Graphene-based materials are promising nonprecious metal catalysts (NPMCs) for oxygen reduction reaction (ORR). However, this kind of carbon materials are usually suffering from layer stacking and intrinsically lack of highly-efficient active sites for ORR. At present, it is still a huge challenge to develop porous multi-doped graphene. Herein, the B, N and Co tri-doped graphene with hierarchical pores is successfully synthesized via a first hydrothermal reaction of graphene oxide (GO) with Co(II) nitrate, 2-methylimidazole (2MI) and boric acid, subsequent pyrolysis and final acid leaching. The morphology, structure and components of a series of samples are systematically investigated. The as-obtained products possess abundant macro/mesopores and ORR active sites including B-bonded C (C B), pyridinic N, graphitic N, Co N C and defects owing to the formation and decomposition of the Co layered double hydroxides (Co-LDHs). After optimizing hydrothermal temperature, pyrolytic temperature and the amount of GO, the sample exhibits an excellent ORR performance in 0.1 M KOH solution. The activity, durability and methanol tolerance are comparable or even superior to those of the commercial Pt/C catalyst (20 wt%). This work provides a new strategy to construct porous multi-doped graphene as nonprecious ORR catalyst. Image 1 [ABSTRACT FROM AUTHOR]

Austenite (γ‐Fe) is thermodynamically unstable at room temperature. Relatively little attention has been directed in the past for the synthesis and properties of γ‐Fe nanoparticles. Herein, we demonstrate a NaOH‐assisted and metal‐organic framework (MOF)‐derived method to prepare a novel catalyst featured by γ‐Fe nanoparticles encapsulated into the porous N‐doped carbon matrix. The Fe atoms doped in the MOF structure play an important role in the formation of stable γ‐Fe. The catalysts exhibit superior catalytic activity with the four‐electron transfer pathway for oxygen reduction reaction (ORR) in alkaline solution. Besides the Fe−Nx sites, γ‐Fe nanoparticles are believed to play an important role in the superior ORR activity. However, it is suggested that the metal nanoparticles are not ORR active species, whereas they may activate the surrounding N/C layers, thus making the N/C layers more active toward ORR. In addition, the oxidized surface of the metal nanoparticles may also act as active species contributing to the ORR activity. A NaOH‐assisted and metal‐organic framework derived method was developed to prepare a novel Fe−N/C catalyst featured by γ‐Fe nanoparticles encapsulated into the porous N‐doped carbon matrix with promising activity toward oxygen reduction. [ABSTRACT FROM AUTHOR]

Development of a neutral Zn–air battery is of much significance due to the high stability of zinc in a neutral electrolyte. Here, Ni/Co-doped C–N nanotube composites (C–N, Ni/C–N, Co/C–N, and Ni–Co/C–N) as efficient oxygen reduction reaction (ORR) electrocatalysts in a neutral medium have been prepared by direct pyrolysis of Ni/Co salt, dicyandiamide (DCD) and glucose. Among the synthesized catalysts, Ni–Co/C–N presents a high ORR current density of 8.5 mA ⋅ cm − 2 in a 0.5 mol ⋅ L − 1 KNO3 solution. The ORR electron transfer number of the catalyst Ni–Co/C–N is 3.8, indicating that O2 is almost completely reduced to H2O. A neutral zinc–air battery utilizing a 0.5 mol ⋅ L − 1 KNO3 solution has been assembled by using the prepared composite catalyst coated on carbon paper as an air cathode, and Zn plate as an anode. The battery with the cathode catalyst Ni–Co/C–N delivers the open-circuit voltage of 1.13 V and the maximum power density of 65 mW ⋅ cm − 2 . The constant discharge current density of 50 mA ⋅ cm − 2 , 100 mA ⋅ cm − 2 and 150 mA ⋅ cm − 2 can last 202 h, 93 h and 11 h, respectively. A stable voltage plateau appears at various discharge current densities. The neutral zinc–air battery can be repeatedly discharged after replacing the zinc anode. Results indicate that the synthesized Ni–Co/C–N catalyst is an excellent cathode material applied to a neutral zinc–air battery, showing broad application prospects as a mobile power source. Ni/Co-doped C–N nanotube composites have been prepared through direct pyrolysis of Ni/Co salt, dicyandiamide and glucose. The Ni–Co/C–N catalyst presents a more uniform size of nanotube particles with diameter as small as 30 nm, and it possesses excellent ORR performance as the cathode catalysts of neutral Zn–air battery. [ABSTRACT FROM AUTHOR]

The development of efficient nonprecious metal catalysts for oxygen reduction reaction (ORR) is crucial but challenging. Herein, one simple and effective strategy is developed to synthesize bimetallic nitrogen-doped carbon catalysts by pyrolyzing Fe-doped Vitamin B12 (VB12) supported carbon black (Fe-VB12/C). A typical Fe 20 -VB12/C catalyst with a nominal iron content of 20 wt% pyrolyzed at 700 °C exhibits remarkably ORR activity in alkaline medium (half-wave potential of 0.88 V, 10 mV positive than that of commercial Pt/C), high selectivity (electron transfer number > 3.93), excellent stability (only 6 mV negative shift of half-wave potential after 5000 potential cycles) and good methanol-tolerance. The superior ORR activity of the composite is mainly attributed to the improved mesoporous structure and co-existence of abundant Fe-N x and Co-N x active sites. Meanwhile, the metallic Fe are necessary for the improved ORR activity by means of the interaction of metallic Fe with neighboring active sites. [ABSTRACT FROM AUTHOR]

A family of bimetallic oxygen reduction catalysts was prepared from N-containing porous synthetic polymers doped with iron chloride and with the chloride of either Cr, Mn, Co, Cu or Zn. The effects of Fe interaction with the additional transition metal and their magnetic characteristics on the catalytic activity in the oxygen reduction reaction (ORR) in alkaline medium were investigated. In addition, the ORR catalyzed by these bimetallic non-precious metal catalysts was studied under an external magnetic field generated by a permanent magnet. Linear sweep voltammetry in stationary conditions showed that the Co co-doped catalysts exhibit the highest activity, strongly enhanced by an external magnetic field applied at a 90° angle relative to the catalyst layer surface. Rotating ring-disk electrode tests (at pH = 13) showed that catalysts co-doped with either Mn or Zn exhibit the highest catalytic activity. In these instances, an external magnetic field decreases the amount of undesirable peroxide intermediate as it increases the number of electrons transferred for ORR. • A Fe–N–C catalyst is co-doped with either Cr, Mn, Co, Cu or Zn. • Dual-doping modifies the magnetic properties of the bimetallic catalysts. • The catalysts' efficiency in the ORR is studied under an external magnetic field. • The magnetic field yields higher selectivity towards the 4e− ORR. [ABSTRACT FROM AUTHOR]

Fuel cell vehicles, the only all-electric technology with a demonstrated >300 miles per fill travel range, use Pt as the electrode catalyst. The high price of Pt creates a major cost barrier for large-scale implementation of polymer electrolyte membrane fuel cells. Nonprecious metal catalysts (NPMCs) represent attractive low-cost alternatives. However, a significantly lower turnover frequency at the individual catalytic site renders the traditional carbon-supported NPMCs inadequate in reaching the desired performance afforded by Pt. Unconventional catalyst design aiming at maximizing the active site density at much improved mass and charge transports is essential for the next-generation NPMC. We report here a method of preparing highly efficient, nanofibrous NPMC for cathodic oxygen reduction reaction by electro-spinning a polymer solution containing ferrous organometallics and zeolitic imidazolate framework followed by thermal activation. The catalyst offers a carbon nanonetwork architecture made of microporous nanofibers decorated by uniformly distributed high-density active sites. In a single-cell test, the membrane electrode containing such a catalyst delivered unprecedented volumetric activities of 3.3 A•cm-3 at 0.9 V or 450 A•cm-3 extrapolated at 0.8 V, representing the highest reported value in the literature. Improved fuel cell durability was also observed. [ABSTRACT FROM AUTHOR]

In this work, carbon-supported cobalt-dicyandiamide (Co-DCD) was synthesized by a simple chemical method followed heat-treated at 600,700, 800, 900, and 1000 °C to acquire electrocatalysts with excellent activity for the oxygen reduction reaction (ORR). The resulting catalysts Co-N/C- T pyrolyzed at 600-1000 °C all showed substantial activities to ORR, and the catalyst heat-treated at 800 °C exhibited the best ORR activity. The catalytic performance of Co-N/ C- T catalysts synthesized with different amounts of DCD as nitrogen source and Co(OAc)⋅4HO as metal precursor were measured by cyclic voltammetry in alkaline electrolyte. The onset potential for oxygen reduction on the optimum catalyst was approximately 0.938 V (vs. RHE) in 0.1 M NaOH solution, higher by 83 mV than that on the commercial catalyst of 20 % JM Pt/C. Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterize the catalyst in terms of the structure and composition in order to sketch the contours of the catalytic active sites of the catalysts. The characterization studies indicate that pyridinic N-C was the most important of the catalytic active sites and responsible for the ORR catalytic activity of Co-N/C- T in alkaline electrolyte. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) was also used to obtain the overall ORR electron transfer number and electron transfer coefficiency. The overall electron transfer number for ORR catalyzed by the optimum catalyst Co-N/C-800 was determined to be 3.47 by CV and 3.89-3.96 by LSV,respectively, suggesting that the ORR was a mixture of two- and four-electron transfer pathways, but dominated by a four-electron transfer process. Based on these measurements and other references, an ORR mechanism was proposed to facilitate further investigation. The results also show that this novel catalyst with ORR excellent activity would have outstanding methanol tolerance and potential application as a kind of nonprecious metal cathodic ORR catalyst for direct methanol fuel cell. [ABSTRACT FROM AUTHOR]

Non-platinum carbon-based catalysts have attracted much more attention in recent years because of their low cost and outstanding performance, and are regarded as one of the most promising alternatives to precious metal catalysts. Activated carbon (AC), which has a large specific surface area (SSA), can be used as a carrier or carbon source at the same time. In this work, stable pine peel bio-based materials were used to prepare large-surface-area activated carbon and then compound with cobalt phthalocyanine (CoPc) to obtain a high-performance cobalt/nitrogen/carbon (Co-N-C) catalyst. High catalytic activity is related to increasing the number of Co particles on the large-specific-area activated carbon, which are related with the immersing effect of CoPc into the AC and the rational decomposed temperature of the CoPc ring. The synergy with N promoting the exposure of CoNx active sites is also important. The Eonset of the catalyst treated with a composite proportion of AC and CoPc of 1 to 2 at 800 °C (AC@CoPc-800-1-2) is 1.006 V, higher than the Pt/C (20 wt%) catalyst. Apart from this, compared with other AC/CoPc series catalysts and Pt/C (20 wt%) catalyst, the stability of AC/CoPc-800-1-2 is 87.8% in 0.1 M KOH after 20,000 s testing. Considering the performance and price of the catalyst in a practical application, these composite catalysts combining biomass carbon materials with phthalocyanine series could be widely used in the area of catalysts and energy storage. [ABSTRACT FROM AUTHOR]

Transition-metal-coordination N-doped carbon (M–N–C) materials have been explored extensively as oxygen reduction reaction (ORR) electrocatlysts, owing to the low price, high conductivity and superior electrocatalytic property. Herein, an effective templating approach is developed for synthesizing high density of FeII–N 4 moiety dispersed in S,N-doped 3D hierarchical porous carbon (3DFe–S,N–C). Due to the high distribution of active sites, the large surface area and the abundant porosity, 3DFe–S,N–C displays a positive half-wave potential of 0.91 V and excellent ORR stability in alkaline medium. As demonstrated in cathode catalyst, 3DFe–S,N–C-based primary Zn–air battery (ZAB) can achieve a maximum power density of 160 mW cm−2 and specific energy density of 974 Wh kg Zn −1. In addition, the as-prepared catalyst also exhibits a potential application in solid-state and flexible ZAB. [ABSTRACT FROM AUTHOR]

The electrochemical oxygen reduction reaction (ORR) is a critical reaction in many energy conversion and storage systems, including fuel cells and metal–air batteries. Nonprecious-metal-based catalysts have captured attention for realizing viable and sustainable devices. However, in Fe-based catalysts, the efficient utilization of active sites, Fe–N x and Fe coated on a carbon layer (Fe@C), is challenging owing to difficulties in controlling these active sites during synthesis. In this study, FeNC electrocatalysts with varying Fe/C ratios show different Fe@C/Fe–N x ratios and ORR activities. Increasing the carbon content increases the Fe–N x site density while decreasing the size of the Fe nanoparticles and the thickness of the carbon coating layer, thus enhancing the ORR activity. As cathode materials for anion exchange membrane fuel cells and Zn–air batteries, the FeNC electrocatalysts exhibit excellent performance when compared to Pt catalysts and previously reported transition-metal-based catalysts. Based on the structural changes observed by in situ X-ray absorption fine structure analysis during electrochemical operation, these catalysts were found to contain electrocatalytically efficient Fe–N 4 sites. This work provides efficient strategies for designing high-performance catalysts for the ORR. Image 1 • High-performance ORR catalysts with both Fe@C and Fe–N 4 active sites are prepared. • Synergetic effect of Fe@C and Fe–N 4 sites improved catalytic activity. • Anion exchange membrane fuel cell with the catalysts showed high performance. • Zn-air battery utilizing the catalysts also exhibited high performance. • In situ XAFS analysis revealed that Fe–N 4 sites are catalytically efficient sites. [ABSTRACT FROM AUTHOR]

This study reports a high-performing nonprecious metal catalyst for the oxygen reduction reaction that is composed of highly dispersed Fe centered active sites on bamboolike carbon nanotubes. NH 2 -MIL-88B is used as the iron source and ZIF-8 as the carbon source. The precursors are uniformly mixed by ball milling, which destroys their crystal structures. A bamboolike carbon nanotube network results from the pyrolysis of the mixed precursors. The morphology is controlled by the proportion of the precursors and the pyrolysis temperature. The catalyst shows excellent oxygen reduction activity in both half-cell and full-cell tests. The onset potential and half-wave potential are 0.96 and 0.78 V vs RHE, respectively. In the fuel cell test, the current density reaches 0.85 A cm -2 at 0.7 V and 1.24 A cm -2 at 0.6 V ( iR -corrected). The novel synthesis approach of the highly dispersed catalyst provides new strategy in the design of high effective nonprecious metal catalysts for fuel cell.

The regioselective C-H arylation of substituted polycyclic aromatic hydrocarbons (PAHs) is a desired but challenging task. A copper-catalyzed C7-H arylation of 1-naphthamides has been developed by using aryliodonium salts as arylating reagents. This protocol does not need to use precious metal catalysts and tolerates wide variety of functional groups. Under standard conditions, the remote C-H arylation of other PAHs including phenanthrene-9-carboxamide, pyrene-1-carboxamide and fluoranthene-3-carboxamide has also accomplished, which provides an opportunity for the development of diverse organic optoelectronic materials., (Copyright © 2020, Luo et al.; licensee Beilstein-Institut.)

Development of highly efficient nonprecious metal (NPM) catalysts for oxygen reduction reaction (ORR) in acidic media is challenging but of great significance. Herein, an effective ORR catalyst based on Fe nanoparticles encapsulated by S,N-codoped few-layer defective carbon (Fe@S,N-DC) was synthesized via a microwave-assisted strategy. The obtained Fe@S,N-DC nanocomposite showed a remarkable electrocatalytic activity toward ORR in acidic media, with a half-wave potential ( E 1/2 ) of +0.785 V versus reversible hydrogen electrode, which was 80 mV more positive than that of the sulfur-free counterpart (Fe@N-DC). Furthermore, due to the protection by the S,N-codoped carbon shell, the Fe@S,N-DC nanocomposite displayed apparent stability with only a 13 mV negative shift of E 1/2 after 10,000 cycles and excellent tolerance to methanol. X-ray absorption near-edge spectroscopy measurements confirmed the formation of multiple defective sites on the S,N-codoped carbon surface and strong interfacial electron transfer from the Fe core to the outer carbon surface, as compared to the sulfur-free counterpart. The enriched electron density on the defective carbon surface of Fe@S,N-DC, induced by the interfacial electron transfer, facilitated the reduction of O 2 to OOH*, leading to enhanced ORR performance. These results shed light on the significance of S doping in Fe-N-C catalysts in the design of high-performance NPM catalysts for ORR in acidic media.

A class of novel CoNC active nanoparticles anchored on 3D hierarchical porous graphene‐like carbon nanosheets compositions (CoNC@3D HPG) with high porosity, high specific surface area, interconnected pores, and a hierarchical pore structure are synthesized, which are perfect as electrochemical electrode scaffolds, giving rise to efficient and rapid pathways for ion and electron transport, which certainly facilitate the mass transport. This hybrid catalyst possesses outstanding oxygen reduction reaction (ORR) activity through a four‐electron transfer process. Most importantly, the ORR activity of this material is superior to Pt/C catalyst, better stability and fuel (methanol and CO) tolerance than Pt/C catalyst. Besides, the CoNC@3D HPG also exhibits outstanding electrocatalytic performance as an efficient hydrogen evolution reaction catalyst with zero onset overpotential, low overpotential at large current density, small Tafel slope, high exchange current density, and excellent durability. It is worth noting that this outstanding bifunctional catalyst is prepared by a novel resin‐based self‐assembly growth methodology at large‐scale. A novel class of Co N C@3D HPG hybrid is dislayed with high porosity, high specific surface area, interconnected pores, and a hierarchical pore structure, which is perfect as oxygen reduction reaction and hydrogen evolution reaction electrode scaffold, and can provide efficient and rapid pathways for ion and electron transport, and certainly facilitate the mass transport. [ABSTRACT FROM AUTHOR]

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., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The synthesis, characterization, and electrocatalytic properties of mesoporous carbon materials doped with nitrogen atoms and iron are reported and compared for the catalyzed reduction of oxygen gas at fuel cell cathodes. Mixtures of common and inexpensive organic precursors, melamine, and formaldehyde were pyrolyzed in the presence of transition-metal salts (e.g., nitrates) within a mesoporous silica template to yield mesoporous carbon materials with greater extents of graphitization than those of others prepared from small-molecule precursors. In particular, Fe,N-doped carbon materials possessed high surface areas (∼800 m 2 /g) and high electrical conductivities (∼19 S/cm), which make them attractive for electrocatalyst applications. The surface compositions of the mesoporous Fe,N-doped carbon materials were postsynthetically modified by acid washing and followed by high-temperature thermal treatments, which were shown by X-ray photoelectron spectroscopy to favor the formation of graphitic and pyridinic nitrogen moieties. Such surface-modified materials exhibited high electrocatalytic oxygen reduction activities under alkaline conditions, as established by their high onset and half-wave potentials (1.04 and 0.87 V, respectively vs reversible hydrogen electrode) and low Tafel slope (53 mV/decade). These values are superior to many similar transition-metal- and N-doped carbon materials and compare favorably with commercially available precious-metal catalysts, e.g., 20 wt % Pt supported on activated carbon. The analyses indicate that inexpensive mesoporous Fe,N-doped carbon materials are promising alternatives to precious metal-containing catalysts for electrochemical reduction of oxygen in polymer electrolyte fuel cells.

Exploring inexpensive and high-performance nonprecious metal catalysts (NPMCs) to replace the rare and expensive Pt-based catalyst for the oxygen reduction reaction (ORR) is crucial for future low-temperature fuel cell devices. Herein, we developed a new type of highly efficient 3D porous Fe/N/C electrocatalyst through a simple pyrolysis approach. Our systematic study revealed that the pyrolysis temperature, the surface area, and the Fe content in the catalysts largely affect the ORR performance of the Fe/N/C catalysts, and the optimized parameters have been identified. The optimized Fe/N/C catalyst, with an interconnected hollow and open structure, exhibits one of the highest ORR activity, stability and selectivity in both alkaline and acidic conditions. In 0.1 M KOH, compared to the commercial Pt/C catalyst, the 3D porous Fe/N/C catalyst exhibits ∼6 times better activity (e.g., 1.91 mA cm -2 for Fe/N/C vs 0.32 mA cm -2 for Pt/C, at 0.9 V) and excellent stability (e.g., no any decay for Fe/N/C vs 35 mV negative half-wave potential shift for Pt/C, after 10000 cycles test). In 0.5 M H 2 SO 4 , this catalyst also exhibits comparable activity and better stability comparing to Pt/C catalyst. More importantly, in both alkaline and acidic media (RRDE environment), the as-synthesized Fe/N/C catalyst shows much better stability and methanol tolerance than those of the state-of-the-art commercial Pt/C catalyst. All these make the 3D porous Fe/N/C nanostructure an excellent candidate for non-precious-metal ORR catalyst in metal-air batteries and fuel cells.

In this work, we present a comprehensive study on the role of metal species in MOF-based Me-N-C (mono- and bimetallic) catalysts for the hydrogen evolution reaction (HER). The catalysts are investigated with respect to HER activity and stability in alkaline electrolyte. On the basis of the structural analysis by X-ray diffraction, X-ray-induced photoelectron spectroscopy, and transmission electron microscopy, it is concluded that MeN 4 sites seem to dominate the HER activity of these catalysts. There is a strong relation between the amount of MeN 4 sites that are formed and the energy of formation related to these sites integrated at the edge of a graphene layer, as obtained from density functional theory (DFT) calculations. Our results show, for the first time, that the combination of two metals (Co and Mo) in a bimetallic (Co,Mo)-N-C catalyst allows hydrogen production with a significantly improved overpotential in comparison to its monometallic counterparts and other Me-N-C catalysts. By the combination of experimental results with DFT calculations, we show that the origin of the enhanced performance of our (Co,Mo)-N-C catalyst seems to be provided by an improved hydrogen binding energy on one MeN 4 site because of the presence of a second MeN 4 site in its close vicinity, as investigated in detail for our most active (Co,Mo)-N-C catalyst. The outstanding stability and good activity make especially the bimetallic Me-N-C catalysts interesting candidates for solar fuel applications.

Herein, we develop a novel method to synthesize evenly dispersed fine Co nanoparticles (CoNPs) (particle size of ∼42 nm) encapsulated in a N-doped porous carbon matrix (NPCM) with superficial N-doped porous carbon nanofibers (NPCNF) (denoted as Co@NPCM/CNF-850) as an oxygen reduction reaction (ORR) electrocatalyst. Such an electrocatalyst is the direct pyrolysis product of the novel pine needle-like ZIF-67-based metal-organic framework nanowire array (MOFNWA) prepared using an inorganic cobalt carbonate hydroxide (Co(CO 3 ) 0.5 (OH)·0.11H 2 O) nanowire array as a linear sacrificial template, which is totally different from the traditional method, that is, using inorganic salts to synthesize MOF particles. Because of the high dispersibility of the effective fine N-doped carbon-wrapped CoNPs (rather than the overlarge CoNP aggregates); the unique linear MOF-derived assemblies, which are beneficial to electronic transmission; the high degree of graphitization, which is attributed to the superficial NPCNF and carbon layers wrapping the CoNPs; as well as the high porosity, our catalyst showed remarkable ORR activity (E onset of 1.033 V vs the reversible hydrogen electrode) in alkaline solution. Besides, our catalyst revealed excellent stability and tolerance of methanol. Furthermore, on the basis of the X-ray absorption near-edge structure, extended X-ray absorption fine structure, and linear sweep voltammetry data, we first provided proof that a catalyst devoid of obvious Co-N x can have superior ORR activity.

The preparation of a low-cost, high-efficient, and stable electrocatalyst as an alternative to platinum for the oxygen reduction reaction (ORR) is especially important to various energy storage components, such as fuel cells and metal-air batteries. Here, we report a new type of bonded double-doped graphene nanoribbon-based nonprecious metal catalysts in which Fe3C nanoparticles embedded in Fe-N-doped graphene nanoribbon (GNRs) frameworks through a simple pyrolysis. The as-obtained catalyst possesses several desirable merits for the ORR, such as diverse high-efficiency catalytic sites, a high specific surface area, an ideal hierarchical cellular structure, and a highly conductive N-doped GNR network. Accordingly, the prepared catalyst shows a superior ORR activity (an onset potential of 0.02 V and a half-wave potential of -0.148 V versus an Ag/AgCl electrode) in alkaline media, close to the commercial Pt/C catalyst. Moreover, it also displays good ORR behavior in an acidic solution.

Tuna is one of the most rapid and distant swimmers. Its unique gill structure with the porous lamellae promotes fast oxygen exchange that guarantees tuna's high metabolic and athletic demands. Inspired by this specific structure, we designed and fabricated microporous graphene nanoplatelets (GNPs)-based Fe/N/C electrocatalysts for oxygen reduction reaction (ORR). Careful control of GNP structure leads to the increment of microporosity, which influences the O2 adsorption positively and desorption oppositely, resulting in enhanced O2 diffusion, while experiencing reduced ORR kinetics. Working in the cathode of proton-exchange membrane fuel cells, the GNP catalysts require a compromise between adsorption/desorption for effective O2 exchange, and as a result, appropriate microporosity is needed. In this work, the highest power density, 521 mW·cm(-2), at zero back pressure is achieved.

Fuel cell vehicles, the only all-electric technology with a demonstrated >300 miles per fill travel range, use Pt as the electrode catalyst. The high price of Pt creates a major cost barrier for large-scale implementation of polymer electrolyte membrane fuel cells. Nonprecious metal catalysts (NPMCs) represent attractive low-cost alternatives. However, a significantly lower turnover frequency at the individual catalytic site renders the traditional carbon-supported NPMCs inadequate in reaching the desired performance afforded by Pt. Unconventional catalyst design aiming at maximizing the active site density at much improved mass and charge transports is essential for the next-generation NPMC. We report here a method of preparing highly efficient, nanofibrous NPMC for cathodic oxygen reduction reaction by electrospinning a polymer solution containing ferrous organometallics and zeolitic imidazolate framework followed by thermal activation. The catalyst offers a carbon nanonetwork architecture made of microporous nanofibers decorated by uniformly distributed high-density active sites. In a single-cell test, the membrane electrode containing such a catalyst delivered unprecedented volumetric activities of 3.3 A ⋅ cm(-3) at 0.9 V or 450 A ⋅ cm(-3) extrapolated at 0.8 V, representing the highest reported value in the literature. Improved fuel cell durability was also observed.

Cost-effective electrocatalysts based on nonprecious metals for efficient water splitting are crucial for various technological applications represented by fuel cell. Here, 3d transition metal layered double hydroxides (LDHs) with varied contents of Ni and Fe were successfully synthesized through a homogeneous precipitation. The exfoliated Ni-Fe LDH nanosheets were heteroassembled with graphene oxide (GO) as well as reduced graphene oxide (rGO) into superlattice-like hybrids, in which two kinds of oppositely charged nanosheets are stacked face-to-face in alternating sequence. Heterostructured composites of Ni2/3Fe1/3 LDH nanosheets and GO (Ni2/3Fe1/3-GO) exhibited an excellent oxygen evolution reaction (OER) efficiency with a small overpotential of about 0.23 V and Tafel slope of 42 mV/decade. The activity was further improved via the combination of Ni2/3Fe1/3 LDH nanosheets with more conductive rGO (Ni2/3Fe1/3-rGO) to achieve an overpotential as low as 0.21 V and Tafel plot of 40 mV/decade. The catalytic activity was enhanced with an increased Fe content in the bimetallic Ni-Fe system. Moreover, the composite catalysts were found to be effective for hydrogen evolution reaction. An electrolyzer cell powered by a single AA battery of 1.5 V was demonstrated by using the bifunctional catalysts.

The applicability of analyzing by Mößbauer spectroscopy the structural changes of Fe-N-C catalysts that have been tested at the cathode of membrane electrode assemblies in proton exchange membrane (PEM) fuel cells is demonstrated. The Mößbauer characterization of powders of the same catalysts was recently described in our previous publication. A possible change of the iron species upon testing in fuel cell was investigated here by Mößbauer spectroscopy, energy-dispersive X-ray cross-sectional imaging, and neutron activation analysis. Our results show that the absorption probability of γ rays by the iron nuclei in Fe-N-C is strongly affected by the presence of Nafion and water content. A detailed investigation of the effect of an oxidizing treatment (1.2 V) of the non-noble cathode in PEM fuel cell indicates that the observed activity decay is mainly attributable to carbon oxidation causing a leaching of active iron sites hosted in the carbon matrix.