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Calcining pristine metal organic frameworks in an open system to synthesize N-doped carbon materials always lead to some drawbacks, such as relatively low graphitization degree and great loss of heteroatoms, and these factors greatly influenced the oxygen reduction performance of catalysts. In this work, a closed calcination method with three steps pathway has been developed to calcine the in-situ synthesized Co-MOF-GO/Urea composite to obtain the highly graphitized and high N content materials as enhanced oxygen reduction catalysts. During the pyrolysis process, the urea not only served as the additional N source, but also played the role of etching the pore structure by using the produced ammonia gas from polycondensation reaction. After careful adjustment the mass ratio of urea and graphene oxide, a Co-GO-C/N catalyst with high specific surface area, increased N content and abundant of pore structure has obtained. When being used for electrochemistry oxygen reduction reaction, the optimal Co-GO(50)-C/N(2.5) catalyst exhibits almost comparable oxygen reduction performance with the Pt/C in alkaline media, and the onset and half-wave potentials of which are 92 mV and 97 mV higher than that of pristine Co-MOF derived Co-GO(0)-C/N(0) catalyst. In addition, it also exhibits excellent methanol and ethanol tolerance and outstanding long-term durability. Image 1 • Co-GO(m)-C/N(n) was synthesized by using a closed calcination method. • Urea served as additional N source to increase the N atoms content of catalyst. • NH 3 derived from urea polycondensation could etch the pore structure of catalyst. • Co-GO(50)-C/N(2.5) possesses high graphitized and high N content characteristics. • The activity of Co-GO(50)-C/N(2.5)) is higher than that of MOFs derived catalyst. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen and fluorine co-doped hierarchical honeycomb-like carbon nanofibers (N F-CNFs-950) are prepared by electro-blown spinning technology and high temperature calcination. It possesses large specific surface area, micro/meso/macro hierarchical through-pore structure, high pyridine-N and graphite-N content. These characteristics make it exhibit an outstanding alkaline electrocatalytic oxygen reduction reaction (ORR) activity (half wave potential of 0.833 V vs reversible hydrogen electrode and current density of 5.48 mA cm−2). In particular, the introduction of the ionic C F/N F successfully avoids the inactivation of pyridine N in the carbon skeleton due to protonation in the acidic electrolyte. And the ionic C F/N F activated pyridine N work synergistically with graphite N to promote N F-CNFs-950 to exhibit an acidic ORR activity (half wave potential of 0.606 V vs reversible hydrogen electrode and current density of 5.58 mA cm−2) that is only second to commercial Pt/C. Importantly, the N F-CNFs-950 catalyst exhibits much better methanol tolerance and electrochemical stability in both alkaline and acidic environments. Graphical abstract Image 1 Highlights • Honeycomb-like N F-CNFs are prepared by EBS technology and carbonization. • Pyrolysis of PTFE provides greater specific surface area and porosity. • Optimized nitrogen and fluorine hybridization state of N F-CNFs are tuned. • N F-CNFs-950 exhibiting superior ORR performance in alkaline and acidic media. [ABSTRACT FROM AUTHOR]

Abstract Iron and nitrogen co-doped carbons show great potential for high-performance electrochemical oxygen reduction reaction. However, the rational design of atomically dispersed iron over nitrogen-doped carbons with activity comparable to that of Pt-C is still challenging. Herein, we develop a new approach that enables the direct formation of intrinsically nitrogen-functionalized two-dimensional sheet-like carbons containing a high concentration of single Fe atoms. This strategy only involves one-step pyrolysis of both, guanine and iron nitrate, without using any guiding agent and sacrificial template. The electrochemistry tests demonstrate an excellent ORR performance of the prepared Fe-N x -C catalyst with a half-wave potential of 0.85 V and a limited current density of −6.5 mA/cm2 in alkaline medium, outperforming the commercial Pt-C and most of previously reported Fe-N x -C catalysts. We believe that the emergence of superior ORR performance is mostly attributed to the uniform dispersion of single Fe atoms at the molecular level and the formation of abundant coordinated Fe-N x sites. In addition, the high surface area, optimal porosity and defective structure (particularly the defects at the edge) of the two-dimensional carbons are also beneficial for the improved ORR activity. Graphical abstract Image 1 Highlights • Nitrogen-doped carbon nanosheets are synthesized by in-situ pyrolysis of biomolecule. • The 2D carbons allow the deposition of highly dispersed single iron atoms. • The prepared Fe-N x -C exhibits outstanding ORR activity. • The coordinated Fe-Nx sites play a key role in the catalysis for ORR. [ABSTRACT FROM AUTHOR]

Because of the urgent need for renewable resources, oxygen reduction reaction (ORR) has been widely studied. Finding efficient and low cost non-precious metal catalyst is increasingly critical. In this study, melamine foam is used as template to obtain porous sulfur and nitrogen-codoped graphene/carbon foam with uniformly distributed cobalt sulfide nanoparticles (Co 1-x S/SNG/CF) which is prepared by a simple infiltration-drying-sulfuration method. It is noteworthy that melamine foam not only works as a three-dimensional support skeleton, but also provides a nitrogen source without any environmental pollution. Such Co 1-x S/SNG/CF catalyst shows excellent oxygen reduction catalytic performance with an onset potential of only 0.99 V, which is the same as that of Pt/C catalyst (E onset  = 0.99 V). Furthermore, the stability and methanol tolerance of Co 1-x S/SNG/CF are more outstanding than those of Pt/C catalyst. Our work manifests a facile method to prepare S and N-codoped 3D graphene network decorated with Co 1-x S nanoparticles, which may be utilized as potential alternative to the expensive Pt/C catalysts toward ORR. [ABSTRACT FROM AUTHOR]

Uniform cobalt and nitrogen co-doped carbon nanospheres (CoN–CNS) with high specific surface area (865 m 2 g −1 ) have been prepared by a simple but efficient method. The prepared CoN–CNS catalyst exhibits outstanding catalytic performance for the oxygen reduction reaction (ORR) in both alkaline and acidic electrolytes. In alkaline electrolyte, the prepared CoN–CNS has more positive half-wave potential and larger kinetic current density than commercial Pt/C. In acidic electrolyte, CoN–CNS also shows good ORR activity with high electron transfer number, its onset and half-wave potentials are all close to those of commercial carbon supported platinum catalyst (Pt/C). CoN–CNS catalyst shows more superior stability and higher methanol-tolerance than commercial Pt/C both in alkaline and in acidic electrolytes. The potassium thiocyanate-poisoning test further confirms that the cobalt-nitrogen active sites exist in CoN–CNS, which are dominating to endow high ORR catalytic activity in acidic electrolyte. This study develops a new method to prepare non-precious metal catalyst with excellent ORR performances for direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Developing efficient, readily available, and sustainable electrocatalysts for oxygen reduction reaction (ORR) in neutral medium is of great importance to practical applications of microbial fuel cells (MFCs). Herein, a porous nitrogen-doped carbon material with encapsulated Fe-based nanoparticles (Fe-N x /C) has been developed and utilized as an efficient ORR catalyst in MFCs. The material was obtained through pyrolysis of a highly porous organic polymer containing iron(II) porphyrins. The characterizations of morphology, crystalline structure and elemental composition reveal that Fe-N x /C consists of well-dispersed Fe-based nanoparticles coated by N-doped graphitic carbon layer. ORR catalytic performance of Fe-N x /C has been evaluated through cyclic voltammetry and rotating ring-disk electrode measurements, and its application as a cathode electrocatalyst in an air-cathode single-chamber MFC has been investigated. Fe-N x /C exhibits comparable or better performance in MFCs than 20% Pt/C, displaying higher cell voltage (601 mV vs. 591 mV), maximum power density (1227 mW m −2 vs. 1031 mW m −2 ) and Coulombic efficiency (50% vs. 31%). These findings indicate that Fe-N x /C is more tolerant and durable than Pt/C in a system with bacteria metabolism and thus holds great potential for practical MFC applications. [ABSTRACT FROM AUTHOR]

Prohibitively expensive precious metal catalysts for oxygen reduction reaction (ORR) have been one of the major hurdles in a wide use of electrochemical cells. Recent significant efforts to develop precious metal free catalysts have resulted in excellent catalytic activities. However, complicated and time-consuming synthesis processes have negated the cost benefit. Moreover, detailed analysis about catalytically active sites and the role of each element in these high-performance catalysts containing nanomaterials for large surface areas are often lacking. Here we report a facile one-step synthesis method of nitrogen-iron coordinated carbon nanotube (CNT) catalysts without precious metals. Our catalysts show excellent long-term stability and onset ORR potential comparable to those of other precious metal free catalysts, and the maximum limiting current density from our catalysts is larger than that of the Pt-based catalysts. We carry out a series of synthesis and characterization experiments with/without iron and nitrogen in CNT, and identify that the coordination of nitrogen and iron in CNT plays a key role in achieving the excellent catalytic performances. We anticipate our one-step process could be used for mass production of precious metal free electrocatalysts for a wide range of electrochemical cells including fuel cells and metal-air batteries. [ABSTRACT FROM AUTHOR]

A novel electrochemical catalyst of phosphorus and nitrogen dual-doped cobalt-based carbon nanofibers (Co N P-CNFs) is prepared by a facile and cost-effective electrospinning technique. Excellent features of the porous carbon nanofibers with large amounts of Co atoms, N/P-doping effect, abundant pyridinic-N and Co N x clusters as catalytic active sites, and the advantages of the structure and composition result in a high catalytic efficiency. In alkaline or acidic media, Co N P-CNFs exhibits remarkable electrocatalytic activities and kinetics for oxygen reduction reaction (ORR), superior methanol tolerance and stability, and a similar four-electron pathway. In addition, Co N P-CNFs also shows excellent performance for hydrogen evolution reaction (HER), offering a low onset potential of −0.216 V and a stable current density of 10 mA cm −2 at potential of −0.248 V. The mechanism of ORR and HER catalytic active site arises from the doping of N/P atoms in the Co-based CNFs, which is responsible for the excellent electrocatalytic performance. Due to the excellent catalytic efficiencies, Co N P-CNFs act as a promising catalyst material for fuel cells and water splitting technologies. [ABSTRACT FROM AUTHOR]

Durability of catalysts for oxygen reduction reaction (ORR) is the key factor for governing the performance of microbial fuel cells (MFCs). The cobalt (Co) chelated polyaniline (PANI) is used as the nitrogen and carbon sources to prepare the N-doped Co/Co 9 S 8 /partly-graphitized carbon (Co/Co 9 S 8 /NPGC) catalysts. Structure-activity correlations for Co/Co 9 S 8 /NPGC are explored by tuning the heating temperature (600–1000 °C) to investigate how the active components (Co/Co 9 S 8 ) and N-doped functionalities (N-species) influence the ORR activity. As temperature increases, the gradual crystallization of Co originating from the reduction of Co 9 S 8 is conducted to form the Co/Co 9 S 8 heterojunction. MFCs with Co/Co 9 S 8 /NPGC (800 °C) cathode obtain the highest power density (1156 mW m −2 ) and the lowest charge transfer resistance (11.1 Ω) after 75 d running, which are better than commercial Pt/C (10 wt.%). Although the sole Co 9 S 8 plays a limited role in ORR, the resulting Co/Co 9 S 8 is found to be indispensable to achieve high activity and durability in MFCs cathodes. The dominant ORR pathways of Co/Co 9 S 8 /NPGC (800 and 900 °C) are the four-electron O 2 reduction, which are attributed to the co-existence of pyridinic N, graphitic N and Co-N x species. These new N-doped metal sulfide/PGC composites show promise for applications in MFCs. [ABSTRACT FROM AUTHOR]

Carbon-supported transition metal/nitrogen (M–N/C) materials are considered as one of the most promising electrocatalysts for the oxygen reduction reaction (ORR) owing to their high ORR electrocatalytic activity, long-term stability, and excellent methanol tolerance. So far only a few examples of such catalysts are prepared from N-containing polymers. Herein, we report a novel Fe–N/C catalyst using a nitrogen-rich polymeric network and iron(II) acetate as the precursors. The porous polymeric network is fabricated by one-step Friedel–Crafts reaction of a low-cost cross-linker, formaldehyde dimethyl acetal, with 2,4,6-tripyrrol-1,3,5-triazine. Compared to commercial Pt/C catalyst, the as-prepared Fe–N/C electrocatalyst exhibits superior ORR activity in alkaline electrolyte, and comparable ORR activity in acidic medium. The results obtained are significant for the development of new Fe–N/C electrocatalysts for fuel cells. [ABSTRACT FROM AUTHOR]

Cost-effective catalysts are of key importance to the successful deployment of microbial fuel cells (MFCs) for electricity generation from organic wastes. Herein, a novel catalyst prepared by one-step synthesis strategy is reported. The catalyst features N-doped bamboo-like carbon nanotube (BCNT) in which CoNi-alloy is encapsulated at the end and/or the middle section of the tube with many graphene layers inside inner cavities of BCNT (N-G@CoNi/BCNT). The prepared N-G@CoNi/BCNT exhibits a high oxygen reduction reaction (ORR) activity with an early onset potential of 0.06 V vs. Ag/AgCl and a comparable exchange current density to that of commercial Pt/C. The excellent catalytic activity is further evidenced by a high electron transfer number of 3.63. When being applied in MFCs, the N-G@CoNi/BCNT yields an average current density of 6.7 A m −2 , slightly lower than that of Pt/C but with a less mass transfer potential loss. The cost of the N-G@CoNi/BCNT for constructing a 1-m 2 cathode electrode is 200 times lower than that of Pt/C. With such a competitive price and excellent electrocatalytic-activity resulting from its unique morphology, CoNi-alloy/nitrogen dopants, considerable specific surface area, and carbon-coated alloy/graphene hybridization, the present catalyst is a promising candidate for ORR catalysts in MFCs for energy recovery from wastes. [ABSTRACT FROM AUTHOR]

Cobalt tetramethoxyphenyl porphyrin and polyacrylonitrile - based catalysts for oxygen reduction reaction were synthesized and characterized by means of SEM, TEM, XPS, BET, limited evaporation method, rotating disc and rotating ring-disc electrode methods. Half-cell and Al-air cell tests were carried out to determine the characteristics of gas-diffusion cathodes. Effect of active layer thickness and its composition on the characteristics of the gas-diffusion cathodes was investigated. Power density of 300 mW cm −2 was achieved for alkaline Al-air cell with an air-breathing polyacrylonitrile-based cathode. [ABSTRACT FROM AUTHOR]

To develop low-cost and high-performance non-precious metal-based oxygen reduction catalysts, we investigate the structure and catalytic performance of industrialized vanadium carbide (VC) and nitrogen doped vanadium carbide (V(C, N)). The structure of VC and V(C, N) were examined by XRD, SEM and XPS tests. Results show that the structures of both VC and V(C, N) are face centered cubic and the crystalline size of V(C, N) is slightly larger than that of VC. Electrochemical tests show that the onset potentials of oxygen reduction of V(C, N) and VC are about 23 mV and 51 mV lower than that of Pt/C catalyst. The polarization and electron transfer number of oxygen reduction under the catalysis of V(C, N) is lower than that of VC. This paper explores a new way for developing low-cost and high-performance catalysts for fuel cells from industrialized transitional metal carbides. [ABSTRACT FROM AUTHOR]

In this work, a N-doped highly porous carbon material with multi-level pores and high activity for oxygen reduction reaction (ORR) is successfully prepared by carbonizing pig bones instead of separated carbon/nitrogen-containing and template precursors. The N-doped porous carbon material has high specific surface area of ca. 562.6 m 2 g −1 . Due to its high surface area and N-doped active sites, the ORR activity of obtained carbon in alkaline media is higher than that of commercial Pt/C catalyst (10 wt.%). In addition, it shows a higher methanol tolerance than Pt/C catalyst and long term-operating stability, rendering it as promising ORR catalyst material for fuel cells. [ABSTRACT FROM AUTHOR]

Nitrogen, phosphorus and Fe doped carbon nanospheres have been synthesized by a facile method in which polyacrylonitrile nanospheres are pyrolyzed in the presence of diammonium phosphate and iron trichloride hexahydrate. The specific surface area of the catalyst is high up to 771.3 m 2 g −1 , and it has a hierarchical micro-meso-macroporous structure. In an alkaline medium, the catalyst exhibits high electrocatalytic activity towards the oxygen reduction reaction (ORR) as well as excellent stability and methanol tolerance—superior in each case to commercial Pt/C catalyst. The effects that adding Fe salt and phosphorus on the structure and performance of the catalyst are also investigated. We suggest that the catalyst's excellent electrocatalytic performance may be attributed to: (1) the synergistic effect, which provides more catalytic sites for the ORR, due to the nitrogen and phosphorus co-doping; (2) the strong promotion by trace Fe residues; and (3) the high surface area and excellent mass transport rate arising from the hierarchical porous structure. [ABSTRACT FROM AUTHOR]

Nitrogen doped carbon nanotubes (NCNTs) with encapsulated Fe 3 C nanoparticles (Fe 3 C@NCNTs) are synthesized by a simple direct pyrolysis of melamine and ferric chloride. The characterization results reveal that Fe 3 C is mainly encapsulated in the interior of NCNTs and N species is mainly distributed on the outside surface of NCNTs. Iron and iron carbide catalyze the growth of NCNTs and are wrapped by carbon to form Fe 3 C@NCNTs. The as-prepared Fe 3 C@NCNTs catalyst exhibits superior oxygen reduction reaction (ORR) activity, excellent methanol tolerance and long-term stability in both acid and alkaline media. It is proven that the doped N is the main active site for ORR and the inner Fe 3 C with outside carbon form the synergetic active site to enhance ORR activity. The ORR mechanism of direct four electron transfer pathway is proved in acid and alkaline media. [ABSTRACT FROM AUTHOR]

A novel electrocatalyst for the oxygen reduction reaction (ORR) is fabricated by directly annealing oxidized carbon nanotubes and tripyrrolyl[1,3,5]triazine in nitrogen. The structural and chemical properties of the resultant N-doped carbon nanotubes (NCNTs) are systematically investigated. The electrocatalytic activity of the NCNTs towards ORR in O 2 -saturated 0.1 M KOH electrolyte is evaluated using rotating disk electrode voltammetry. The results demonstrate that the as-prepared NCNT-900 (annealed at 900 °C) exhibits excellent electrochemical performance towards ORR in alkaline medium with an onset potential of −0.038 V ( vs Ag/AgCl), a high kinetic current density of 31.26 mA cm −2 at −0.25 V, a dominant four-electron transfer mechanism (n = 3.88 at −0.25 V), and excellent methanol tolerance and durability. The results obtained are significant for the development of N-doped carbon-based electrocatalysts for alkaline fuel cells. [ABSTRACT FROM AUTHOR]

Efficient electrocatalyst of oxygen reduction reaction (ORR) is crucial for a variety of renewable energy applications and heteroatom-doped carbon materials have demonstrated promising catalytic performance towards ORR. In this paper we report a bioinspired method to synthesize nitrogen/sulfur (N/S) co-doped graphene as an efficient ORR electrocatalyst via self-polymerization of polydopamine (PDA) thin layer on graphene oxide sheets, followed by reacting with cysteine and finally thermal annealing in Argon (Ar) atmosphere. As-prepared N/S co-doped graphene exhibits significantly enhanced ORR catalytic activity in alkaline solution compared with pristine graphene or N-doped graphene. It also displays long-term operation stability and strong tolerance to methanol poison effect, indicating it a promising ORR electrocatalyst. [ABSTRACT FROM AUTHOR]

Two catalysts are synthesized by wet impregnation of multi walled carbon nanotubes (MWCNT) with a complex formed between Co(II) ions and the nitrogen-containing molecule 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ), followed by one or two identical heat treatments in N 2 atmosphere at 800 °C for 3 h. Catalysts are fully characterized by FESEM, EDX, BET, XRD, FTIR, TGA, XPS analyses, and electrochemical techniques. The electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalysts in acid conditions is assessed by means of a rotating disk electrode (RDE) apparatus and a specific type of cell equipped with a gas diffusion working electrode (GDE). In both testing approaches, the catalyst heat-treated twice (Co-N/MWCNT-2) exhibits higher electroactivity than the catalyst heat-treated once (Co-N/MWCNT-1). Chronoamperometries both in RDE and GDE cell are also performed, showing less electroactivity decay and better current performance for the catalyst heat-treated twice. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanofibers (NCNFs) are prepared by the thermal treatment of carbon nanofibers (CNFs) using urea as nitrogen source. Scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy have been employed to characterize the morphology and composition of CNFs and NCNFs. Compared with CNFs, NCNFs display thinner diameter, rougher surface and higher content of pyrrolic-N. As a metal-free catalyst for ORR, NCNFs exhibit comparable catalytic activity, significantly enhanced long-time stability and selectivity in comparison with commercial available Pt/C catalyst. Importantly, the self-supported NCNFs films could be conveniently utilized for electrode modification which is attractive in fuel cells. This work offers a promising metal-free catalyst as an alternative for Pt/C catalyst. [ABSTRACT FROM AUTHOR]

The successful commercialization of fuel cells requires the efficient electrocatalyst to make the oxygen reduction reaction (ORR) fast because of the sluggish nature of ORR and the high cost of the platinum catalysts. In this work, we report the excellent performance of metal-free nitrogen-doped porous carbon nanosheets (NPCN) with hierarchical porous structure and a high surface area of 1436.02 m 2 g −1 for catalyzing ORR. The active NPCN is synthesized via facile high-temperature carbonization of natural ginkgo leaves followed by purification and ammonia post-treatment without using additional supporting templates and activation processes. In O 2 -saturated 0.1 M KOH solution, the resultant NPCN exhibits a high kinetic-limiting current density of 13.57 mA cm −2 at −0.25 V (vs. Ag/AgCl) approaching that of the commercial Pt/C catalyst (14 mA cm −2 ) and long-term electrochemical stability. Notably, the NPCN shows a slightly negative ORR half-wave potential in comparison with Pt/C (Δ E 1/2 = 19 mV). The excellent electrocatalytic properties of NPCN originate from the combined effect of optimal nitrogen doping, high surface area, and porous architecture, which induce the high-density distribution of highly active and stable catalytic sites. [ABSTRACT FROM AUTHOR]

Currently, the development of nitrogen (N) doped carbon based non-precious metal ORR catalysts has become one of the most attractive topics in low temperature fuel cells. Here, we demonstrate a green synthesis route of N-self-doped carbon materials by using eggs as N sources combining with iron sources and multi-walled carbon nanotubes (CE–Fe–MWNT). After carbonized, such hybrid materials possess an outstanding electrocatalytic activity towards ORR comparable to the commercial Pt/C catalyst in alkaline media, and both superior stability and fuel (methanol and CO) tolerance than the commercial Pt/C catalyst, which provide a promising alternative to noble metal catalysts by using abundant natural biological resources. [ABSTRACT FROM AUTHOR]

Abstract: Hierarchical porous iron and nitrogen co-doped carbons (HP–Fe–N–Cs) as efficient cathode catalysts for oxygen reduction reaction (ORR) in neutral media are reported. The HP–Fe–N–Cs are prepared by using polypyrrole as nitrogen source and poly(vinyl alcohol) (PVA) hydrogel-based composites as in-situ templates. In studying the effect of the iron and the hierarchical porous structure on the nitrogen-doped carbon support for ORR, we find that HP–Fe–N–Cs show more positive onset potential, higher cathodic current density, and higher electron transfer number for the ORR in neutral media than iron-free hierarchical porous nitrogen-doped carbon (HP–N–C) and non-hierarchical porous iron and nitrogen co-doped carbon (Fe–N–C), highlighting the importance of the iron and the hierarchical porous structure for improving the ORR performance. Furthermore, HP–Fe–N–Cs show better durability than the commercial Pt/C catalysts in neutral media, and the microbial fuel cells (MFCs) equipped with HP–Fe–N–Cs catalysts on cathodes exhibit comparable power outputs with those of MFCs with commercial Pt/C cathode catalysts. [Copyright &y& Elsevier]

Abstract: Melamine-derived N-doped mesoporous carbon (MNMC) is synthesized by the pyrolysis of lysine and melamineunder at nitrogen atmosphere using ferric chloride as a dopant and SiO2 nanoparticles as hard templates to form mesoporous architecture. The N content in the bulk of carbon materials is as high as 11.3% and ca. 40.6% of N is in the form of pyridinic-N. The surface area of MNMC is ca. 650 m2 g−1 with a pore size distribution in the range of 2.2–34.5 nm. Compared to commercial Pt/C (20 wt%), MNMC exhibits much better electrocatalytic activity, better durability, and higher methanol tolerance for oxygen reduction reaction (ORR) in alkaline medium. Particularly, the onset ORR potential and half-wave ORR potential of MNMC are 1.059 and 0.871 V vs. RHE respectively, which are higher than those of commercial Pt/C. [Copyright &y& Elsevier]

A cost-effective chemical, N,N′-bis(salicylidene)ethylenediamine (salen), is used as a ligand to form a carbon-supported Co-salen complex (Co-salen/C) by a simple solid-sate reaction. The Co-salen/C is then pyrolyzed at 600, 700, 800, 900, and 1000 °C to form carbon-supported Co–N–S/C catalysts for the oxygen reduction reaction (ORR). XRD, EDX, TEM, and XPS are used to characterize the catalysts' composition, crystalline nature, morphology, and possible surface groups induced by heat-treatment. Investigation of the catalytic activity and the ORR mechanisms using rotating disk electrode and rotating ring-disk electrode techniques demonstrates that all of these Co–N–S/C catalysts are highly active for the ORR in an O2-saturated 0.1 M KOH solution, but the catalyst heat treated at 700 °C gives the best ORR activity. The overall electron transfer number for the catalyzed ORR was determined to be 3.6–3.9, with 3.7–19.9% H2O2 production over the potential range of −0.05 to −0.60 V, suggesting that the ORR catalyzed by Co–N–S/C catalysts is dominated by a 4-electron transfer pathway from O2 to H2O. In addition, these catalysts exhibit superior methanol tolerance to commercial 40% Pt/C catalyst, thus the Co–N–S/C catalysts are promising for use as electrocatalysts in alkaline polymer electrolyte membrane fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen doped holey graphene (NHG), with in-plane holes in its sheet plate, has been synthesized in this work through the potassium hydroxide (KOH) etching and ball milling of nitrogen doped graphene (NG). It shows that the KOH etching and ball milling does not distinctly alter the elemental composition and the relative percentages of functional groups in NG, but produce holes in its in-plane sheet plate. The obtained NHG can then be used as an active electrode material for supercapacitors and as an active electrocatalyst for oxygen reduction reaction, and exhibits significantly higher electrochemical performance than the corresponding NG. Its improved electrochemical performance could be attributed to its specific holey structure in the sheet plate and porous structure in its randomly stacked solid, which provide it with more active edge atoms, better accessibility to electrolyte, larger accommodation space for ions, faster electrolyte diffusion and movement and so on. [Copyright &y& Elsevier]

Abstract: A highly active electrocatalyst for oxygen reduction reaction, manganese modified glycine derivative-carbon (Mn-CN x ), is synthesized by a two-step carbonizing process. X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy are used to characterize structure and morphology of the catalysts. Electrochemical tests show that Mn-CN x has higher catalytic activity for oxygen reduction reaction than CN x derived glycine and Mn modified Vulcan carbon. Moreover, the half-wave potential of Mn-CN x is only 12 mV lower than that of commercial Pt/C. Mn-CN x also has excellent durability to methanol crossover in alkaline solution, and thus provides a promising low cost, non-precious metal cathode catalyst for fuel cells. [Copyright &y& Elsevier]

Abstract: Well defined nitrogen-doped graphene (NG) is prepared by a transfer doping approach, in which the graphene oxide (GO) is deoxidized and nitrogen doped by the vaporized polyaniline, and the GO is prepared by a thermal expansion method from graphite oxide. The content of doped nitrogen in the doped graphene is high up to 6.25 at% by the results of elements analysis, and oxygen content is lowered to 5.17 at%. As a non-precious metal cathode electrocatalyst, the NG catalyst exhibits excellent activity toward the oxygen reduction reaction, as well as excellent tolerance toward methanol. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the oxygen reduction reaction reach 0.98 V (vs. RHE), 0.87 V (vs. RHE) and 5.38 mA cm−2, respectively, which are comparable to those of commercial 20 wt% Pt/C catalyst. The well defined graphene structure of the catalyst is revealed clearly by HRTEM and Raman spectra. It is suggested that the nitrogen-doping and large surface area of the NG sheets give the main contribution to the high ORR catalytic activity. [Copyright &y& Elsevier]

Abstract: Nitrogen-doped hollow mesoporous carbon spheres has been synthesized from mesoporous silica spheres using glycine as carbon and nitrogen precursor. The wall of the spheres is composed by broken graphene. The metal free nitrogen-doped hollow mesoporous carbon spheres are proven to be active electrocatalyst for the oxygen reduction reaction in alkaline solution. A unique advantage of the nitrogen-doped hollow mesoporous carbon sphere is its methanol-tolerant property because of the absence of active metal. The catalytic activity is ascribed to the pyridinic-nitrogen formed during pyrolysis and the graphene-like structure. To the best of our knowledge this is the first report on the nitrogen-doped hollow mesoporous carbon sphere as a metal-free electrocatalyst for the oxygen reduction reaction which is an important reaction in fuel cell. The prepared mesoporous carbon material can also be used as catalyst support and find application both in the anode and cathode of fuel cell. [Copyright &y& Elsevier]

Abstract: Spillover, a well-known phenomenon in heterogeneous catalysis referring to the transport of the adsorbed intermediates over the catalyst/support interface, could enhance the catalytic performance by providing additional active sites. Here, we report the spillover-promoted electrocatalytic activity of Pt supported on nitrogen-doped carbon black (NCB) for the oxygen reduction reaction (ORR). By treating Vulcan XC-72R carbon black (CB) at 600 °C under gaseous NH3, NCB of near 1 at% surface nitrogen content is obtained. The catalyst of Pt supported on NCB (Pt/NCB) exhibits simultaneously smaller particle sizes and higher electrochemical surface area and electrocatalytic activity for the ORR than the catalyst of Pt supported on pristine CB (Pt/CB) prepared with the same impregnation method. Particularly, the activity enhancement of Pt/NCB over Pt/CB surpasses that expected due to the surface area increase, which seems to conflict with the common belief that Pt nanoparticles of smaller sizes would have lower area specific activities for the ORR. Cyclic voltammetric responses of these catalysts implied that the oxygenated adsorbates formed on Pt can transport to surface of the NCB support, which may be responsible for the increased area specific activity of the Pt/NCB catalyst. [Copyright &y& Elsevier]

Electrocatalyst is the pivotal component promoting the kinetics of oxygen reduction reaction in aqueous metal-air batteries. However, the content of increased bond as the active species is usually limited by the metal loading, tiny pore canal, insufficient nitrogen further restraining the electrocatalytic effectiveness of single-atom catalysts in oxygen reduction reaction (ORR). Herein, Co, N-dual doped carbon (Co/NNC) is prepared by a versatile strategy of the combination approach of SiO 2 template with extra nitrogen source. Based on ZIF-67 prepared with the assistance of SiO 2 template, the extra nitrogen source was introduced in the high-temperature pyrolysis procedure. The material characterizations of XRD, SEM, HRTEM, BET, Raman and XPS are conducted to synthetically analyze the functional role of extra nitrogen source. Moreover, the Co/NNC with increased Co-N x active sites is employed into two aqueous metal-air batteries of Zn-air and Mg-air batteries, which exhibits excellent performances especially in the aspects of discharge specific capacity, discharge stability and power density. [Display omitted] 1 SiO 2 template and extra nitrogen source are combined to prepare Co/NNC. 2 Extra nitrogen source boosts the Co-N x content of Co/NNC derived from ZIF-67. 3 In aqueous metal-air batteries, Co/NNC shows superior capacity performance than Pt/C. [ABSTRACT FROM AUTHOR]

Abstract: Pt nanoparticles supported on nitrogen-doped porous carbon microspheres (Pt/CN) were synthesized via an in-situ spray-drying technique followed by calcination. The addition of ammonium hydroxide had a remarkable influence on the solution chemistry, which promoted the simultaneous formation of metallic Pt and nitrogen doping onto carbon support material. Furthermore, the precursor pH influenced the subsequent oxygen reduction activity of the product. Ultrahigh oxygen reduction reaction (ORR) activity was recorded for a catalyst prepared at a precursor pH of 8.4 with mass activity and specific activity were 564 mA mg−1 Pt and 834 μA cm−2 Pt, respectively. This investigation resulted in an effective strategy to escalate the catalyst ORR during limited catalyst surface area enhancement. [Copyright &y& Elsevier]

Abstract: Nitrogen-doped graphene (NG) materials have been prepared by hydrothermal reaction of graphite oxide (GO) with urea, and their electrocatalytic properties towards oxygen reduction reaction in 0.1 M KOH are investigated. The introduction of urea leads to successful nitrogen insertion in the form of pyridinic, pyrrolic, and graphitic bonding configurations with enhanced reduction of GO, and an increase in the mass ratio between urea and GO gives higher nitrogen contents, which is accompanied by more defects in microstructure. Reduction of O2 to OH− at lower overpotentials is favored by the incorporation of nitrogen, and the activity of NG is closely associated with nitrogen contents and microstructure. NG materials with ca. 7% nitrogen contents and moderate defect densities prepared from mass ratios of 1:200 and 1:300 (GO/urea) show the best performance. [Copyright &y& Elsevier]

Abstract: The aligned nitrogen-doped carbon nanotubes (NCNT) with bamboo-like structure are synthesized via thermal chemical vapor deposition using melamine and urea as different nitrogen precursors. Meanwhile, ferrocene is used as catalyst and carbon precursor. The resulting NCNT with melamine (M-NCNT) have shown superior ORR performance in terms of limiting current density and number of electrons transferred. Further characterizations by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy illustrated higher nitrogen content and more defects in M-NCNT compared to that in NCNT with urea (U-NCNT), which indicate the important role of the nitrogen precursor in nitrogen content and structure of NCNT. It is concluded that higher nitrogen content and more defects of NCNT lead to high performance of ORR. [Copyright &y& Elsevier]

Abstract: In this work, iron- and nitrogen-functionalized graphene (Fe–N–G) as a non-precious metal catalyst is synthesized via a facile method of thermal treatment of a mixture of Fe salt, graphitic carbon nitride (g-C3N4) and chemically reduced graphene. The electrocatalytic activity of the prepared catalysts toward oxygen reduction reaction (ORR) evaluated by using linear sweep voltammetry tests shows that the Fe–N–G catalyst has more positive onset potential and increased reduction current densities as compared to the pristine graphene (P–G) catalyst, indicating an enhanced ORR activity of the Fe–N–G catalyst. More importantly, the Fe–N–G-MFC achieves the highest power density of 1149.8mWm−2, which is ∼2.1 times of that generated with the Pt/C-MFC (561.1mWm−2) and much higher than that of the P–G-MFC (109mWm−2). These results demonstrate that the Fe–N–G catalyst can hold the promise of being an excellent alternative to the costly Pt catalyst for practical MFC applications. [Copyright &y& Elsevier]

Abstract: This study examines the role of transition metals (Co or Fe) on nitrogen-modified carbon-based catalysts for the oxygen reduction reaction (ORR). The nitrogen-modified carbon-based catalysts are synthesized by the pyrolysis process in the presence of polypyrrole (PPy) and ethylenediamine (ED) with different amounts of transition metals. Electrochemical data and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis do not support that the transition metal itself behaves as an active site for ORR. The X-ray photoelectron spectroscopy (XPS) and elemental analysis results show that the total nitrogen content and the active nitrogen functional groups, such as pyridinic-N and graphitic-N, are strongly dependent on the type of transition metal and the amount of transition metal used. Therefore, it is believed that transition metals serve to catalyze the formation of active nitrogen functional groups for the ORR by doping nitrogen into carbon. [Copyright &y& Elsevier]

Abstract: Oxygen- and nitrogen-containing groups are successfully introduced onto the carbon nanofiber (CNF) surfaces by sonochemical treatment in mixed acids (concentrated sulfuric acid and nitric acid) and ammonia, respectively. Pt electrocatalysts supported on the acid-treated CNF (CNF-O) and ammonia-treated CNF (CNF-ON) are prepared and the effect of CNF surface functional groups on the electrocatalytic activities of supported catalysts for oxygen reduction reaction (ORR) is investigated. High resolution transmission electron microscopy reveals that Pt particles are uniformly dispersed on the two CNF supports and the CNF-ON supported Pt nanoparticles have a smaller average particle size and a more uniform particle size distribution. Cyclic voltammetric analysis shows the Pt/CNF-ON has a larger electrochemically active surface area than Pt/CNF-O. Rotating disk electrode measurements show that the Pt/CNF-ON exhibits a considerably higher electrocatalytic activity toward ORR as compared with Pt/CNF-O. It is believed that the good electrocatalytic activity of Pt/CNF-ON can be attributed to the smaller Pt particle size and more uniform particle size distribution, to the synergistic effect and the enhanced Pt–CNF-ON interaction, and to the unique structural and electronic properties of CNF-ON. [Copyright &y& Elsevier]

Abstract: ‘Carbon Alloy Catalysts’ (CAC), non-precious metal catalysts for the oxygen reduction reaction (ORR), were prepared from various kinds of nitrogen-containing rigid-rod aromatic polymers, polyimides, polyamides and azoles, by carbonization at 900°C under nitrogen flow. The catalytic activity for ORR was evaluated by the onset potential, which was taken at a current density of −2μAcm−2. Carbonized polymers having high nitrogen content showed higher onset potential. In particular, CACs derived from azole (Az5) had an onset potential of 0.8V, despite being was prepared without any metals. [Copyright &y& Elsevier]

Microbial fuel cell (MFC), a new technology, uses microorganisms to decompose and oxidize the organic matter for bioelectricity generation. However, the sluggish oxygen reduction reaction of cathode catalyst is an important factor that affects electricity generation. Herein, nitrogen-enriched hydrothermal carbon doped with transition metal and sulfur heteroatoms was prepared. Carbon doped with iron, cobalt and nickel metal particles and nitrogen and sulfur heteroatoms (Fe-NSC, Co-NSC, Ni-NSC) exhibited maximum power densities of 2068 ± 32 mW m−2, 1736 ± 49 mW m−2 and 1441 ± 45 mW m−2, respectively. By analyzing the content and bonding configuration of nitrogen, sulfur, iron, cobalt and nickel, it is further verified that pyridinic nitrogen and graphitic nitrogen can reduce the charge transfer resistance, and iron–nitrogen (Fe–N) bonding and cobalt–nitrogen (Co–N) bonding are considered to be active sites which are beneficial to enhance oxygen reduction activity, while nickel–nitrogen (Ni–N) bonding is insensitive to oxygen reduction activity. Consequently, Fe-NSC is an effective catalyst for oxygen reduction reaction in MFC. [Display omitted] • N, S and transition metal (Fe, Co, Ni) co-doped carbon is synthesized. • The maximum power density of Fe-NSC is 2068 ± 32 mW m−2. • Fe, Co nanoparticles provide more effective active sites than Ni nanoparticles. • Fe-NSC and Co-NSC are four-electron ORR processes. [ABSTRACT FROM AUTHOR]

Two porous carbon supports as N-doped carbon (NC) and Fe/N-co-doped carbon (Fe-NC), are obtained from ZIF-8 (zeolitic imidazolate framework) and Fe@ZIF-8, respectively, through the pyrolysis process. They are then decorated with transition metals using a modified polyol method to precipitate Fe, Co, and Fe–Co nanoparticles. The as-prepared catalysts are characterized by different physicochemical, morphological, and electrochemical characterization methods. Field emission scanning electron microscopy images show well-defined preserved polyhedron morphology for all prepared catalysts. Transmission electron microscopy images confirm a uniform distribution of metal nanoparticles through the surface of the supports. X-ray photoelectron spectroscopy results illustrate the existence of high content of graphitic and pyridinic nitrogen. Oxygen reduction reaction (ORR) results show the prepared support, which is in-situ doped with iron (Fe-NC), has better ORR performance than NC support. The results also display Co and Fe nanoparticles' coincident precipitation on the supports can improve ORR. This finding indicates both in-situ and ex-situ metal doping can be beneficial for good ORR performance. The optimum catalyst (Fe–Co/Fe-NC) illustrates enhanced ORR activity and stability with onset potential ~0.9V RHE in 0.1 M HClO 4. Superior performance is associated with a synergistic effect between small and uniform dispersion of Co and Fe nanoparticles and appropriate nitrogen content. [Display omitted] • Zeolitic imidazolate framework (ZIF) as precursor for ORR electrocatalyst. • Transition metal nanoparticles (Fe, Co, Fe–Co) precipitated on MOF-derived porous carbon. • Fe–N-doped carbon derived from pyrolyzed (Fe@ZIF-8) precursor acts as a better support. • The acceptable ORR performance observed for Fe–Co NPs on Fe-doped support in acidic media. [ABSTRACT FROM AUTHOR]

The Zn-air battery is a promising next-generation battery because of the higher energy density and safety compared with the Li-ion battery. However, the Zn-air battery suffers from huge energy loss and poor cycling performance, which are due to the sluggish kinetics of oxygen reduction/evolution reactions (ORR/OER) and the instability of bifunctional catalysts. The state-of-the-art bifunctional catalyst is the composite of Pt and Ir/Ru oxides, which is hindered by the scarce resource and high cost. Therefore, developing low-cost and high-efficient bifunctional non-noble metal-based catalysts is essential to the deployment of Zn-air batteries. Herein, we report a dual-nitrogen-source mediated pyrolysis route to rationally design and synthesize the hybrid Co/Co–N–C bifunctional catalyst. The tailored catalyst consisting of carbon confined Co nanoparticles and atomically dispersed Co–N–C moiety is identified. Remarkably, the dual-nitrogen-source derived Co/Co–N–C catalyst demonstrates excellent electrochemical performances with a half-wave potential of 0.882 V for ORR and a potential of 1.640 V at 10 mA cm−2 for OER; reasonably, the bifunctionality of Co/Co–N–C, which is supported by the excellent self-breathing Zn-air battery performance (the maximum energy density of 897.1 Wh kg Zn −1; no obvious degradation within 167h cycling). The abundant Co-Nx sites and metallic Co nanoparticles synergistically boost the ORR and OER. Image 1 • A dual-nitrogen-source method is proposed to synthesize porous Co-based catalysts. • The dual nitrogen sources play different roles in morphology and structure control. • The hybrid carbon-confined Co nanoparticles and Co-N x sites are well tailored. • The good bifunctionality is due to the hybrid active site configuration. • Excellent performance and lifetime are obtained in a Zn-air battery. [ABSTRACT FROM AUTHOR]

Developing high-efficiency and economical non-PGM catalysts for oxygen reduction reaction (ORR) is of great significance for energy conversion and storage devices. In this work, a template-free strategy has been developed to prepare Fe, N co-doped hollow spherical carbon (FeNHSC) with a certain curvature, through a simple hydrothermal method and then NH 3 activation. The obtained FeNHSC exhibits remarkably improved ORR activity, good long-term stability, and outstanding resistance to methanol crossover, which are much higher than the commercial Pt/C in alkaline medium. The enhancement of the above electrocatalytic performances can be attributed to the curved shell of the synthesized hollow spherical carbon, which contributes to exposure active Fe in form of the Fe–N 4 moieties anchored on the carbon. Density functional theory (DFT) calculation results further reveal that the FeNHSC with a curved structure can efficiently boost the ORR rate, compared with the non-curved carbon. For the curved carbon, the positively shifted d -band center (ε d) and increased positive surface charges of the Fe sites in form of Fe–N 4 structure should be responsible for the curvature-dependent ORR activity. This finding may open a way to fabrication next-generation transition metal-nitrogen-carbon catalysts for clean energies. • Fe, N co-doped hollow spherical carbon was synthesized by a template-free method. • The catalyst shows excellent ORR activity and high stability in alkaline media. • It exhibits good power density and discharge performance for Zn-air batteries. • DFT results reveal that the curved shell of the carbon results in the performance. [ABSTRACT FROM AUTHOR]

Exploring efficient, cost-effectiveness and stable bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical for rechargeable metal-air batteries. Herein, CoFe alloyed nanocrystals encapsulated in N, P-codoped carbon nanovesicles assembled hollow spheres (CoFe@NP-CHS) are prepared by pyrolyzing the homogenous mixture of vitamin B12 (VB12), melamine and Fe 2 O 3 at 700 °C. The resultant CoFe@NP-CHS demonstrates distinct activity for ORR and OER in the alkaline media. More impressively, the as-developed Zn-air battery displays excellent performance with enhanced open-circuit voltage of 1.516 V, enlarged peak power density of 123.1 mW cm−2, and remarkable cycling stability at 10 mA cm−2 (40 h), outperforming the mixture of commercial Pt/C + RuO 2 catalysts. This work provides a promising avenue to fabricate efficient, low cost and stable electrocatalyst for practical viability in electrochemical energy devices. Image 1 • Hollow spheres were assembled with CoFe in N, P-doped carbon nanovesicles. • The hollow structures provided extra active sites and enlarged active area. • The catalyst showed excellent catalytic activity and stability for ORR and OER. • The as-assembled Zn-air battery had high power density and long-term durability. [ABSTRACT FROM AUTHOR]

Recently, advanced nitrogen-containing carbon materials create a huge opportunity for developing efficient catalysts, and show great potential in zinc-air batteries (ZABs). In this study, YF 3 doped nitrogen-containing carbon (YF 3 @NC) electrocatalyst is prepared using m-phenylenediamine as nitrogen and carbon sources. Yttrium chloride, ammonium fluoride and l -arginine are used as Y source, F source and assistant, respectively. Spherical YF 3 precursor is obtained through a facile arginine-assisted hydrothermal method, which is then coated with nitrogen-containing carbon and pyrolyzed at high temperature to fabricate YF 3 @NC. It exhibits a positive onset potential (0.943 V), half-wave potential (0.836 V), high current density and good cycling stability (10 h degradation: 13%). When YF 3 @NC is applied as air cathode electrode in ZABs, the obtained battery has a high open circuit potential (1.478 V) and peak power density (75 mW cm−2). This approach makes YF 3 @NC to be a promising candidate as cathode catalyst in ZABs in the future. Image 1 • YF 3 doped nitrogen-containing carbon material (YF 3 @NC) was prepared. • The optimized YF 3 @NC exhibits superior ORR activity and stability. • YF 3 @NC-driven zinc air battery shows high-efficient performance. [ABSTRACT FROM AUTHOR]

The present report demonstrates a simple approach for the synthesis of efficient metal-free electrocatalysts of nitrogen- and sulfur-codoped carbon materials (N–S-DPCs) via carbonization of thiazolothiazole based conjugated microporous polymer precursors (XWB-CMP). The precursors are composed of densely populated thiazolothiazole units that uniformly decorate over the micropore surface and can be readily converted into novel N–S-DPCs with a uniform nitorgen/sulfur distribution by template-free pyrolysis. The electrochemical characterization demonstrates that N–S-DPCs obtained at pyrolysis temperature of 1000 °C exhibits a high electrocatalytic activity toward oxygen reduction reaction (ORR), superior durability, good methanol tolerance as compared to the commercial Pt/C catalyst. The present work sheds insights into the effects of heteroatom doping on ORR electrocatalysts. Image 1 • These efficient metal-free electrocatalysts was synthesized via carbonization. • XWB-CMP is composed of densely populated thiazolothiazole units. • XWB-CMP-1000 exhibits a higher electrocatalytic activity toward ORR. [ABSTRACT FROM AUTHOR]

Here, for the first time, graphene-like porous carbon nanosheets have been constructed by triethanolamine intercalation of layered peanut seed coats followed by simultaneously thermal exfoliation and pyrolysis. The as-prepared carbon nanosheets (GPCN-PSC-900) possess graphene-like nanostructure (with thickness of ~4 nm), high BET surface area (887 m2 g−1), and abundant nitrogen doping (3.4 at.%), which benefit the improvement of conductivity (8.1 S cm−1) and wettability. Due to these merits, the GPCN-PSC-900-based supercapacitor shows ultra-high rate capabilities (76.3% and 72.5% of capacity retention at 1–200 A g−1) and excellent stabilities (94.7% and 92.3% of capacity retention after 20,000 cycles at 10 A g−1) in 6.0 M KOH and 1.0 M Na 2 SO 4 electrolytes, respectively. Furthermore, the GPCN-PSC-900 also exhibits excellent ORR activity (E 0 = 0.970 V; E 1/2 = 0.829 V vs. RHE) and high stability in alkaline media, which make it an efficient air cathode for the Zn–air battery. This work presents a new kind of GPCNs that derive from renewable biomass (peanut seed coats) for energy storage and conversion. A renewable graphene-like porous carbon nanosheet (GPCNs) has been constructed by using triethanolamine intercalation followed by simultaneous thermal exfoliation and pyrolysis from natural layered peanut seed coats. The as-prepared GPCN-PSC-900 electrode exhibited ultra-high rate capability and excellent stability in both alkaline and neutral electrolytes. Furthermore, the GPCN-PSC-900, serves as electrocatalyst towards ORR, exhibits excellent activity and stability in alkaline media. Image 1 • A novel graphene-like porous carbon nanosheets (GPCNs) was prepared from biomass. • The GPCNs was constructed by triethanolamine intercalation followed by pyrolysis. • The GPCNs based supercapacitor exhibited ultrahigh-rate capability at 1–200 A g−1. • The GPCNs showed excellent ORR electrocatalytic activity in alkaline media. [ABSTRACT FROM AUTHOR]

In this work, polyacrylonitrile (PAN) and metal-organic framework (MOF)-derived 3D B and N codoped core-shell carbon nanofibers (CNFs) with multiscale carbon layers derived from continuous zeolitic imidazolate frameworks (ZIF-8 and ZIF-67) are synthesized via dual-functional ZnO and Co 3 O 4 nanostructures. Here, ZnO and Co 3 O 4 act as a metal-ion source for the MOF formation and as pore creating agents. Further, dual-function NaBH 4 reduces metallic ions into respective metals as well as providing three-dimensionality to the conventional two dimensional CNF mat. Additionally, B and N doping can be achieved by treatment with a single dopant, NH 4 HB 4 O 7 ·3H 2 O. The resulting core-shell multiscale-3D CNFs with hierarchical pores (ZIF-8@BN-CNF) deliver exceptional onset (0.94 V vs RHE) and half wave potential (0.86 V vs RHE)) with excellent cyclic stability toward the oxygen reduction reaction (ORR). Moreover, the electrode maintained a remarkably high current retention of 97.2%, even after 25 000 s, which is better than that of a commercial Pt/C catalyst (89.6%). The superior catalytic activity and stability of the CNF-based catalyst are attributed to the synergistic effect of the structure and codoping of B and N with highly porous 3D hierarchical core-shell nanoarchitecture. Image 1 • 3D-porous B and N codoped core-shell CNFs are fabricated from PAN/MOFs moiety. • Hierarchical-3D CNFs electrodes are employed as metal-free electrocatalyst for ORR. • ZIF-8@BN-CNF electrode delivers highly positive half wave potential (0.86 V vs RHE). • The catalyst also delivers excellent stability and methanol tolerance activity. [ABSTRACT FROM AUTHOR]

Developing high-performance and low-cost catalysts for oxygen reduction reaction (ORR) in metal-air batteries is challenging but necessary for their practical applications and commercialization. In this paper, a core-shell cobalt nanoparticles-embedded honeysuckle-like N-doped carbon nanotube (Co@NCNT) catalyst is synthesized through programmed carbonization with the plasma etching. The Co@NCNT displays a uniform core-shell honeysuckle-like nanostructure and exhibits comparable ORR performance to the commercial 20% Pt/C. The onset potential (E onset) and half-wave potential (E 1/2) of the Co@NCNT is 1.030 V and 0.872 V (vs. RHE), and the potential decay in E 1/2 is only 9 mV after 5000 cycles accelerated durability test (ADT). Moreover, a Zinc-air battery (ZAB) with Co@NCNT cathode catalyst exhibits a peak power density of 162.5 mW cm−2 and high rate capability as well as excellent durability. The excellent performance of the Co@NCNT is mainly attributed to the synergistic effect of unique core-shell nanostructure, more defects and active sites as well as more tiny rifts in the carbon-shell induced by the plasma etching. • Non-noble electrocatalysts for Oxygen Reduction Reaction (ORR). • The Co@NCNT-300-5 displays uniform core-shell honeysuckle-like nanostructure. • Co@NCNT-300-5 exhibits superior ORR activity and Zinc-air battery performance. [ABSTRACT FROM AUTHOR]