Facile preparation of Fe3C decorate three-dimensional N-doped porous carbon for efficient oxygen reduction reaction

Novel Fe₃C nanoparticles that decorate three-dimensional N-rich porous carbon (Fe₃C@3DNC) catalysts were designed and synthesized by double templates assisted high-energy ball milling and subsequent high-temperature pyrolysis for the oxygen reduction reaction (ORR). NaCl and Na₂SiO₃ are used as the mixed template while Fe(NO₃)₃·9H₂O and 2-Methylimidazole were used as the iron, nitrogen and carbon sources. The optimized Fe₃C@3DNC catalyst (Fe₃C@3DNC-1-900) had good ORR performance in alkaline medium, with an Eonest value of 0.968 V and E_1/2 value of 0.861. In addition, the catalytic process exhibited selectivity–nearly four-electron transfer kinetics and possesses a lower Tafel slope compared to commercial Pt/C catalyst as well as good methanol tolerance. In addition, the Fe₃C@3DNC-1-900 catalyst also had excellent ORR activity (E_1/2 = 0.72 V) and long-term stability (the half-wave potential only occurs at 10 mV after 5000 cycles) in acidic media. The good catalytic performance of the Fe₃C@3DNC-1-900 catalyst can be attributed to the 3D hierarchically porous structure and extremely high number of active sites around the porous carbon. The double template assisted high-energy ball milling strategy can be a promising and scalable method to prepare three-dimensional porous carbon-based composite materials for energy conversion and storage applications.     

Amino functionalized carbon nanotubes supported CoNi@CoO–NiO core/shell nanoparticles as highly efficient bifunctional catalyst for rechargeable Zn-air batteries

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the core reaction processes of rechargeable Zn-air battery (ZAB) cathode. Therefore, exploring a bifunctional catalyst with excellent electrochemical performance, high durability, and low cost is essential for rechargeable ZAB. In this work, amino functionalized carbon nanotubes supported core/shell nanoparticles composed of CoNi alloy core and CoO–NiO shell (CoNi@CoO–NiO/NH₂-CNTs-1) is synthesized through a simple and efficient hydrothermal reaction and calcination method, which shows higher ORR/OER bifunctional catalytic performance than the single metal-based catalyst, such as Ni@NiO/NH₂-CNTs and Co@CoO/NH₂-CNTs. The fabricated bimetallic alloy based catalyst CoNi@CoO–NiO/NH₂-CNTs-3 with the optimized loading content of CoNi@CoO–NiO core/shell nanoparticles, presents the best bifunctional catalytic performance for ORR/OER. Experimental studies reveal that CoNi@CoO–NiO/NH₂-CNTs-3 exhibits the onset potential of 0.956 V and 1.423 V vs. RHE for ORR and OER, respectively. It also exhibits a low overpotential of 377 mV to achieve a 10 mA cm^?2 current density for OER, and positive half-wave potentials of 0.794 V for ORR. And the potential difference between half-wave potential of ORR (E_1/2) and the potential at 10 mA cm^?2 for OER (E_j10) is 0.813 V. In addition, when CoNi@CoO–NiO/NH₂-CNTs-3 is used as an air electrode catalyst of rechargeable ZAB, its maximum power density and open circuit voltage (OCV) can reach 128.7 mW cm^?2 and 1.458 V (The commercially available catalyst of Pt/C–RuO₂ is 88.1 mW cm^?2), which strongly demonstrates that the fabricated catalyst CoNi@CoO–NiO/NH₂-CNTs-3 can be used as a highly efficient bifunctional catalyst for ZABs, and is expected to replace those expensive precious metal electrocatalysts to meet the growing demand for new energy devices.     

A novel 3D hybrid carbon-based conductive network constructed by bimetallic MOF-derived CNTs embedded nitrogen-doped carbon framework for oxygen reduction reaction

The rational design of novel non-precious oxygen reduction reaction (ORR) electrocatalysts with good catalytic activity for energy conversion devices is under the spotlight of current research. Herein, we designed and fabricated a novel 3D Co-derived CNTs embedded nitrogen-doped carbon framework (denoted as Co-CNTs@NCF_T, where T represents the pyrolysis temperature) as an efficient ORR catalyst by pyrolysis of the bimetallic metal-organic framework (MOF) in the presence of graphene oxide (GO). The optimized catalyst furnishes large specific surface area, outstanding electrical conductivity and rapid mass transport rates during reactions. Because of these synergistic advantages, the Co-CNTs@NCF₉₀₀ exhibits excellent ORR catalytic activity in terms of a high onset potential of 0.96 V and a half-wave potential of 0.84 V in alkaline electrolyte, outperforming the commercial Pt/C. Furthermore, the Co-CNTs@NCF₉₀₀ manifests good stability and methanol tolerance comparable to the commercial Pt/C catalyst. The presented strategy open up a new avenue for the synthesis of novel electrocatalysts derived from MOF materials for energy-related applications.     

Favorable pore size distribution of biomass-derived N,S dual-doped carbon materials for advanced oxygen reduction reaction

Metal-free carbon materials offer prominent performance towards the oxygen reduction reaction (ORR). The pore size distribution of carbons plays the vital role in promoting the electrocatalytic property. Herein, a succession of N, S dual-doped carbons decorated with 3D interpenetrated hierarchically porous structure are successfully obtained through utilizing ZnCl₂ and Zn(OH)₂ as porogens during carbonizing biomass-wastes. The nanopore amounts with specific sizes can be manipulated through changing diverse biomass-wastes as precursors, while different pore sizes can be optimized by tuning the dosage ratios of ZnCl₂ to Zn(OH)₂. Accompany with the increased amounts of nanopores with sizes of 4.6, 12, 17 and 27 nm, the ORR activity of carbon materials has been significantly promoted. These suitable pore sizes ensure the highly effecient mass transfer through providing abundantly accessible delivery channels and reactive zones for ORR-related intermediates. The optimized catalyst delivers the excellent ORR activity with a half-wave potential of 0.83 V vs. RHE as well as the remarkable long-term stability and methanol resistance ability in alkaline medium. Moreover, two series-connected Zn-air batteries with the catalysts can continuously lighten 216 LEDs over 24 h. The application of biomass-wastes to synthesize N, S dual-doped hierarchical porous carbons is beneficial for achieving the goals of turning waste into treasure.     

Reduced graphene oxide supported Fe2B as robust catalysts for oxygen reduction reaction

Transition metal borides have great potential to be low-cost, high-performance catalysts for novel energies despite the synthesis is rather difficult. In this paper, the reduced graphene oxide (rGO) supported iron boride (Fe₂B/rGO) based catalysts are synthesized by a facile reduction method. The successful synthesis of Fe₂B is confirmed by X-ray diffraction, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photo-electron spectroscopy (XPS) and other tests. HRTEM tests showed that the constructed Fe₂B was embedded in the rGO, where B played the role of coordination atoms which could regulate the electronic structure of the catalysts and improve the catalytic performance towards oxygen reduction reaction (ORR). The electrochemistry tests showed that the peak current intensity of the Fe₂B/rGO catalyzed ORR could be reached up to 7.6 mA/cm², which surpassed that of the Pt/C (20 wt%) catalyst. The current intensity can be kept at 82.47% after continuous running 20,000 s, which is higher than the Pt/C catalyst (79.4%). The onset potential reaches up to 0.95 V, which is only 0.06 V lower than that of Pt/C (20 wt%) catalyst. Both RDE and RRDE tests confirmed that the Fe₂B/rGO catalyzed ORR major happed through 4-electron pathway. The redistributed electron between iron and boron atoms promoted the happening of ORR on Fe₂B/rGO catalysts. The results of this work provide a novel way to develop high performance transition metal boride based catalysts for ORR.     

One-step carbonization of ZIF-8 in Mn-containing ambience to prepare Mn,N co-doped porous carbon as efficient oxygen reduction reaction electrocatalyst

Economical and efficient non-noble metal catalysts should be developed practically, instead of commercial Pt/C for fuel cells. In this paper, manganese, nitrogen co-doped porous carbon (Mn–N–C) was synthesized to catalyze oxygen reduction reaction (ORR) through the one-step carbonization of ZIF-8 in the Mn-containing (MnCl₂) atmosphere. During the carbonization process, MnCl₂ gas was captured with ZIF-8 and then transformed into uniform Mn–N active sites distributed in the porous carbon materials. The Mn–N–C catalyst exhibited plentiful porous structures, large specific surface areas, high graphitization and conductivity, which contributed to the transfer and transport of charge and exposed more active sites. The Mn–N–C catalyst exhibited superior catalytic ability in alkaline and acidic solutions. Half-wave potential of the Mn–N–C could reach 0.88 and 0.73 V in 0.1 M KOH and 0.5 M H₂SO₄, respectively. In addition, the Mn–N–C catalyst showed a prominent stability after the stability test of 18,000 s. Excellent electrochemical performance and endurance make the Mn–N–C expect to be an effective ORR catalyst to build high-performance fuel cells.     

Efficient oxygen reduction electrocatalysis on Mn3O4 nanoparticles decorated N-doped carbon with hierarchical porosity and abundant active sites

Transition metal on nitrogen-doped carbons (M-N-C, M = Fe, Co, Mn, etc.) are a group of promising sustainable electrocatalysts toward oxygen reduction reaction (ORR). Compared to its Fe, Co analogues, Mn–N–C possesses the advantage of being inert for catalyzing Fenton reaction, and thus is expected to offer higher durability, but its ORR activity needs essential improvement. Herein, an efficient Mn–N–C ORR catalyst composed of Mn₃O₄ nanoparticles supported on nitrogen-doped carbon was successfully synthesized by pyrolysis of cyanamide/Mn-incorporated polydopamine (PDA) film coated carbon black (CB), where the presence of N-rich cyanamide confers abundant Mn-N_x active sites and rich micropore/mesopores to the catalyst. In an alkaline medium, as-synthesized Mn–N–C electrocatalyst outperforms commercial Pt/C catalyst in terms of onset potential (0.98 V, vs. RHE), half-wave potential (0.868 V, vs. RHE), and limiting current density. Meanwhile, it exhibits excellent durability and resistance to methanol. In a Zinc-air primary battery, it demonstrates better performance as a cathodic catalyst than Pt/C.     

Fabricating carbon nanocages as ORR catalysts in alkaline electrolyte from F127 self-assemble core-shell micelle

In order to reduce the cost of oxygen reduction reaction (ORR) catalyst in fuel cell, polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) three-block copolymer (F127) and Zn(OH)₂ were used as carbon resource and morphology retaining agent to prepare porous nanocages for ORR catalyst in alkaline solution. Its composition and microstructure were characterized by X-ray diffraction Raman spectroscopy (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) method. Electrochemical properties were evaluated in O₂ saturated alkaline solution. Results showed the sample obtained at 700 °C (C-700) was composed of porous carbon nanocages with diameter of 50 nm and shell thickness of 4 nm. C-700 had the maximum surface area (1011 m² g⁻¹) and the best ORR catalytic performance. The main reason is that polypropylene oxide (PPO) group at the lipophilic end begins to decompose at 500 °C, and the polyethylene oxide (PEO) group at the lipophilic end at 700 °C decomposes completely. In O₂ saturated 0.1 M KOH solution, C-700's oneset potential, limit current density and half-wave potential, which were 0.89 V, 5.59 mA/cm²@0.45 V and 0.71 V, respectively, were close to that of commercial 20% Pt/C catalyst. It was noted that the oneset potential and half-wave potential of C-700 had barely change, and limit current density attenuated about 87.8% after 2000 CV cycle. The obtained catalyst behaved good catalytic activity and stability for ORR in alkaline solution and a potential application prospect in fuel cells.     

Promising nature-based nitrogen-doped porous carbon nanomaterial derived from borassus flabellifer male inflorescence as superior metal-free electrocatalyst for oxygen reduction reaction

In this present study, novel hierarchical nitrogen-doped porous carbon for use as a metal-free oxygen reduction reaction (ORR) electrocatalyst is derived from borassus flabellifer male inflorescences by calcining at 1000 °C in an inert atmosphere using metal hydroxides as activating agent and melamine as nitrogen doping agent. The BET surface areas of the lithium-ion (Li-ion), potassium-ion (K-ion) and calcium-ion (Ca-ion) activated carbon are observed to be 824.02, 810.88 and 602.88 m² g^-1 respectively. Another interesting fact is that the total surface energy calculated by wicking method (73.2 mJ/m²), is found to be higher for Li-ion activated carbons. Among the prepared nitrogen-doped porous carbon, Li-ion activated system, showed an outstanding performance in ORR reaction in alkaline medium, thanks to its high surface area and notable surface activity. An incontrovertible of note that ORR half-wave potential of Li-ion activated nitrogen-doped carbon (0.90 V) is relatively higher in comparison to the commercial 20 wt % Pt/C catalyst (0.86 V). Inspite of overwhelming performance, the ORR reaction followed the preferred 4- electron transfer mechanism involving in the direct reduction pathway in all activated carbons. The ORR performance is also noticeably better and comparable to the best results in the literature based on biomass derived carbon catalysts.     

Fe–N–Si tri-doped carbon nanofibers for efficient oxygen reduction reaction in alkaline and acidic media

The most ideal substitute for Pt/C to catalyze the oxygen reduction reaction (ORR) is the transition metal and nitrogen co-doped carbon-based material (TM-N-C). However, large particles with low catalytic activity are formed easily for the transition metals during high-temperature carbonization. Herein, PAN nanofibers uniformly distributed with FeCl₃ were coated with SiO₂ and then carbonized to obtain Fe–N–Si tri-doped carbon nanofibers catalyst (Fe–N–Si-CNFs). The SiO₂ can further anchor the Fe atoms, thus preventing agglomeration during the carbonization process. Meanwhile, Si atoms have been doped in CNFs during this process, which is conducive to the further improvement of catalytic performance. The Fe–N–Si-CNFs catalyst has a 3D network structure and a large specific surface area (809.3 m² g⁻¹), which contributes to catalyzing the ORR. In alkaline media, Fe–N–Si-CNFs exhibits superior catalytic performance (E_1/2 = 0.86 V vs. RHE) and higher stability (9.6% activity attenuation after 20000s) than Pt/C catalyst (20 wt%).     

Molecule-confined modification of graphitic C3N4 to design mesopore-dominated Fe-N-C hybrid electrocatalyst for oxygen reduction reaction

To design inexpensive carbon catalysts and enhance their oxygen reduction reaction (ORR) activity is critical for developing efficient energy-conversion systems. In this work, a novel Fe-N-C hybrid electrocatalyst with carbon nanolayers-encapsulated Fe₃O₄ nanoparticles is synthesized successfully by utilizing the molecular-level confinement of graphitic C₃N₄ structures via hemin biomaterial. Benefiting from the Fe-N structure prevalent on the carbon nanosheets and large mesopore-dominated specific surface area, the synthesized catalyst under optimized conditions shows excellent electrocatalytic performance for ORR with an E_ORR at 1.08 V versus reversible hydrogen electrode (RHE) and an E_1/2 at 0.87 V vs. RHE, and outstanding long-term stability, which is superior to commercial Pt/C catalysts (E_ORR at 1.04 V versus RHE and E_1/2 at 0.84 V versus RHE). Moreover, the low hydrogen peroxide yield (<11%) and average electron transfer number (~3.8) indicate a four-electron ORR pathway. Besides, the maximum power density of the home-made Zn-air battery using the obtained catalyst is 97.6 mW cm⁻². This work provides a practical route for the synthesis of cheap and efficient ORR electrocatalysts in metal-air battery systems.     

Soybean milk derived carbon intercalated with reduced graphene oxide as high efficient electrocatalysts for oxygen reduction reaction

Exploring high-performance and low-cost metal-free oxygen reduction reaction (ORR) catalysts from biomass-derived materials is vital to the development of novel energy conversion devices such as fuel cells, etc. Herein, nitrogen-enriched soybean milk derived carbon (BDC/rGO-HT-NH₃) intercalated with reduced graphene oxide (rGO) electrocatalyst is prepared via one-pot hydrothermal synthesis method followed with nitridation by NH₃. The resultant catalyst with high surface area, good conductivity and high content of N (9.4 at.%) shows high electrocatalytic activity towards ORR in alkaline medium, which mainly happens through the direct 4-electron pathway. The onset potential of BDC/rGO-HT-NH₃ catalyzed ORR is 0.96 V vs RHE, which is only 0.11 V lower than that of the commercial Pt/C (20 wt%) catalyst. In addition, the BDC/rGO-HT-NH₃ catalyst shows superior long-term running durability. The desirable catalytic performances enable the facile synthesis approach of BDC/rGO-HT-NH₃ to be a promising methodology for transforming other biomass materials to N-enriched carbon based materials as low-cost and environmental friendly catalysts for ORR.     

ZIF-L-Co@carbon fiber paper composite derived Co/Co3O4@C electrocatalyst for ORR in alkali/acidic media and overall seawater splitting

Green and clean energy technologies, including fuel cells, metal-air batteries, water splitting et al., are becoming more significant for our lives. Oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are key reaction processes for fuel cells, metal-air batteries and water splitting. Therefore, it is highly desirable to design a multifunctional catalyst, which owns catalytic performance under a widely applied range. Herein, we demonstrate a novel multifunctional catalyst (Co/Co₃O₄@C) by carbonizing a composite material constructed of zeolite imidazolate framework and carbon fiber paper (ZIF-L-Co@CP). It is a carbon-based material containing metallic Co and Co₃O₄ as a low-cost and effective catalyst toward the ORR and overall water splitting. For ORR, the Co/Co₃O₄@C catalyst shows high half-wave potential in both alkaline and acidic media, 0.823 V for 0.1 M KOH and 0.672 V for 0.1 M HClO₄. More importantly, it exhibits good catalytic activities of hydrogen and oxygen evolutions to perform overall splitting in actual seawater.     

Template-assisted polymerization-pyrolysis derived mesoporous carbon anchored with Fe/Fe3C and Fe−NX species as efficient oxygen reduction catalysts for Zn-air battery

Constructing highly efficient and durable non-noble metal modified carbon catalysts for oxygen reduction reaction (ORR) in the whole pH range is essential for energy conversion devices but still remains a challenge. Herein, the Fe/Fe₃C nanoparticles and Fe-N_X species anchored on the interconnected mesoporous carbon materials are fabricated through an economical and facile template-assisted polymerization-pyrolysis strategy. The catalyst exhibits unique features with the electronic interaction between Fe/Fe₃C and Fe−N_X, large specific surface area and high mesoporous structure as well as nitrogen doping in porous carbon skeletons, which can effectively catalyze ORR over the full pH range. In an alkaline electrolyte, the optimized catalyst displays favorable ORR performance with positive onset potential (E_onset = 0.91 V), half-wave potential (E_1/2 = 0.83 V), long-term cycles stability and methanol tolerance, exceeding those for the commercial Pt/C. Furthermore, the prepared catalyst could be directly assembled into the alkaline Zn−air battery that exhibits the open-circuit voltage of 1.44 V, high power density of 96.0 mW cm⁻² and long-term durability. Therefore, the template-assisted polymerization-pyrolysis strategy provides a promising route for designing high-performance non-noble metal decorated ORR electrocatalysts.     

Soybean powder enables the synthesis of Fe–N–C catalysts with high ORR activities in microbial fuel cell applications

The development of microbial fuel cells (MFCs) into a new type of carbon-neutral wastewater treatment technology requires efficient and low-cost oxygen reduction reaction catalysts in air cathodes. The use of raw soybean powder was investigated for synthesizing Fe–N–C ORR catalysts in a sacrificial SiO₂ support method. ZnCl₂ etching in the synthesis was found to facilitate the formation of hierarchical porous structures of Fe–N–C catalysts. Fe–N–C(1-1) catalyst synthesized with an optimal soybean/ZnCl₂ mass ratio of 1:1 exhibited the highest ORR activity in air cathodes. The use of the obtained Fe–N–C(1-1) catalyst enables a maximum power production of ~0.480 mW cm⁻² in MFCs, higher than commercial Pt/C (0.438 mW cm⁻²) with the same catalyst loading of 2 mg cm⁻². Long-term MFC operations demonstrated that the Fe–N–C synthesized from raw soybean have high stability and toxic tolerance, indicating that abundant low cost soybean biomass is a potential material for ORR catalyst development in MFC applications.     

One-step prepared prussian blue/porous carbon composite derives highly efficient Fe–N–C catalyst for oxygen reduction

Preparation of high-efficiency oxygen reduction reaction (ORR) catalysts with abundant and inexpensive biomass materials have been a hot research topic. We use nitrogen-rich lentinus edodes and potassium ferrate (K₂FeO₄) to simultaneously activate the carbon material and prepare prussian blue (PB), and a porous carbon composite (PB/C) containing PB is synthesized. Finally, using ammonium chloride (NH₄Cl) as a nitrogen source to further synthesize a Fe–N–C catalyst (PB/CN₁T₈₀₀) containing a trace amount of Fe for ORR. Results show that the prepared PB/CN₁T₈₀₀ catalyst forms a coral-like structure, which mainly contains mesopores and possesses a large specific surface area of approximately 1582 m² g⁻¹. Moreover, the onset potential of PB/CN₁T₈₀₀ is 0.95 V, and the half-wave potential is 0.83 V, which are consistent with those of commercial Pt/C. Thus the PB/CN₁T₈₀₀ material is an ORR catalyst with excellent performance. This work provides a basis for simple and efficient conversion of rich biomass into PB/porous carbon composites to prepare highly efficient catalysts.     

Highly active electrocatalysts for oxygen reduction from carbon-supported copper-phthalocyanine synthesized by high temperature treatment

The active, carbon-supported copper phthalocyanine (CuPc/C) nano-catalyst, as a novel cathode catalyst for oxygen reduction reaction, is synthesized via a combined solvent-impregnation along with the high temperature treatment. The catalytic activities of both pyrolyzed and unpyrolyzed catalysts are screened by linear sweep voltammetry (LSV) employing a rotating disk electrode (RDE) technique to quantitatively obtain the oxygen reduction reaction (ORR) kinetic constants and the reaction mechanisms. The results show that heat-treatment can significantly improve the ORR activity of the catalyst, and the optimal heat-treated temperature is around 800 °C, under which, an onset potential of 0.10 V and a half-wave potential of −0.05 V are achieved in alkaline electrolyte. Besides the ORR kinetic rate is increased, the ORR electron transfer number is also increased from 2.5 to 3.6 with increasing heat-treatment temperature from 600 to 800 °C. Also, the effect of catalyst loading in the catalyst layer on the corresponding ORR activity is also studied, and finds that increasing the catalyst loading, the catalyzed ORR kinetic current density can be significantly increased. For a fully understanding of this heat-treatment temperature effect, XRD, TEM, SEM–EDX, TG and XPS are used to identify the catalyst structure and composition. TG results demonstrated that the presence of Cu prevents phthalocyanine from thermal decomposition, thus contribute to higher nitrogen content which can form more Cu–N_x activity sites for the ORR. XPS analysis indicates that both pyridinic-N and graphitic-N may be responsible for the enhanced ORR activity.     

Atomically dispersed Co atoms in nitrogen-doped carbon aerogel for efficient and durable oxygen reduction reaction

Developing non-noble-metal-based electrocatalysts as alternatives to replace Pt-based catalysts for oxygen reduction reaction (ORR) is crucial for large scale industrial application of fuel cells. Herein, we report a facile method to synthesize atomically dispersed Co atoms anchored on nitrogen-doped carbon aerogels with a 3D hierarchically porous network structure via F127-assisted pyrolysis of a phenolic resin/Co²⁺ composite and subsequent HCl etching treatment. HRTEM, AC-STEM, XRD, XPS, and Raman spectroscopy measurements demonstrate that Co atoms are homogeneously atomically dispersed on nitrogen-doped carbon aerogels within the porous structure by coordination with pyridinic-N. Among a series of samples, the Co-NCA@F127-1: 0.56 catalyst exhibits an enhanced ORR activity with onset potential (E_onset) of 0.935 V vs. RHE, the high diffusion limiting current density of 5.96 mA cm⁻² at 0.45 V, as well as an excellent resistance to methanol poisoning and good long-term stability in alkaline medium, comparable to the state-of-the-art Pt/C catalyst. This work may provide a novel and ingenious thought in the design and engineering of efficient and robust electrocatalysts based on single transition-metal atoms supported by nitrogen-doped carbon materials.     

Imidazole polymerized ionic liquid as a precursor for an iron-nitrogen-doped carbon electrocatalyst used in the oxygen reduction reaction

A class of non-precious metal and highly efficient catalysts (Fe–N(PIL)/C) for the oxygen reduction reaction (ORR)were prepared by a two-step reaction involving polymerization and one-pot high-temperature pyrolysis reaction. The characteristics of Fe–N(PIL)/C electrocatalyst samples were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). Additionally, the electrocatalytic properties were tested by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Under alkaline conditions, the Fe–N(PIL)/C catalyst exhibited a 2D-mesoporous structure with prominent catalytic activity. The E_on and E_1/2 reached 1.08 V and 0.93 V (vs. a reversible hydrogen electrode), respectively. The catalyst showed excellent ORR catalytic performance and stability and is superior to a 20 wt% Pt/C catalyst. This could be attributed to its mesoporous structure and the high content of Fe–N activity sites that enable it to carry out a nearly 4e⁻ reaction pathway for the ORR.     

Manganese coordinated with nitrogen in aligned hierarchical porous carbon for efficient electrocatalytic oxygen reduction reaction in alkaline and acidic medium

A Mn coordinated with N atoms aligned hierarchical porous carbon catalyst is prepared through an inorganic metal salt sublimation doping strategy. Gelatin is served as a carbon source and N source, Ca²⁺ is acted as templates to establish aligned porous structure during carbonization. MnCl₂ sublimates into gas to serve as Mn source after reaching the melting point. This method can effectively avoid the agglomeration of Mn atoms, which is beneficial to form Mn-N_x active sites. The prepared optimal catalyst exhibits a large specific surface area with an aligned hierarchical porous structure. XAFs result demonstrates that Mn coordinates with N atoms to form Mn-N_x configuration in the carbon structure. Notably, it exhibits outstanding catalytic ORR performance with a positive half-wave potential (0.86 V vs. RHE) and excellent durability, superior to Pt/C (20 wt%) catalyst under alkaline medium. Meanwhile, enhanced catalytic ORR performance and stability in an acidic medium are also achieved.