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1.
The development of nonprecious metal-based electrocatalysts with remarkable catalytic activity and long-cycling lifespan toward oxygen reduction reaction (ORR) and evolution reaction (OER) is especially important for rechargeable zinc–air batteries (ZABs). Herein, monodispersed Co9S8 nanoparticles embedded in nitrogen-doped hierarchically porous hollow carbon spheres (Co9S8 NPs/NHCS) are synthesized through a template-assisted strategy followed by a co-assembly, thermal annealing, and sulfurization process. Benefiting from larger specific surface area, hierarchically porous hollow structure, and carbon nanotubes self-growth, the obtained Co9S8 NPs/NHCS-0.5 electrocatalyst exhibits decent performance for ORR (E1/2=0.85 V) and OER (E10=1.55 V). A rechargeable ZAB assembled using the Co9S8 NPs/NHCS-0.5 as air cathode delivers a maximum power density of 116 mW cm−2, high open circuit voltage of 1.47 V, and good durability (no obvious voltage decay after 1200 cycles (200 hours)). Such a hierarchically porous hollow structure of Co9S8 NPs/NHCS-0.5 provides a confined space shell and an interconnected hollow core to achieve outstanding bifunctional catalytic activity and cycling stability, which surpass the benchmark Pt/C-RuO2.  相似文献   

2.
The electrochemical synthesis of hydrogen peroxide (H2O2) via a two-electron (2 e) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy-intensive anthraquinone process. Herein, we develop a facile template-protected strategy to synthesize a highly active quinone-rich porous carbon catalyst for H2O2 electrochemical production. The optimized PCC900 material exhibits remarkable activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2 e ORR performance. The effectiveness of chair-form quinone groups as the most efficient active sites is highlighted by the molecule-mimic strategy and theoretical analysis.  相似文献   

3.
The exploration of inexpensive and efficient catalysts for oxygen reduction reaction (ORR) is crucial for chemical and energy industries. Carbon materials have been proved promising with different catalysts enabling 2 and 4e ORR. Nevertheless, their ORR activity and selectivity is still complex and under debate in many cases. Many structures of these active carbon materials are also chemically unstable for practical implementations. Unlike the well-discussed structures, this work presents a strategy to promote efficient and stable 2e ORR of carbon materials through the synergistic effect of lattice distortion and H-passivation (on the distorted structure). We show how these structures can be formed on carbon cloth, and how the reproducible chemical adsorption can be realized on these structures for efficient and stable H2O2 production. The work here gives not only new understandings on the 2e ORR catalysis, but also the robust catalyst which can be directly used in industry.  相似文献   

4.
Iron phthalocyanine (FePc) with unique FeN4 site has attracted increasing interests as a promising non-precious catalyst. However, the plane symmetric structure endows FePc with undesired catalytic performance toward the oxygen reduction reaction (ORR). Here, we report a novel one-dimensional heterostructured ORR catalyst by coupling FePc at polyoxometalate-encapsulated carbon nanotubes (FePc-{PW12}@NTs) using host-guest chemistry. The encapsulation of polyoxometalates can induce a local tensile strain of single-walled NTs to strengthen the interactions with FePc. Both the strain and curvature effects of {PW12}@NT scaffold tune the geometric structure and electronic localization of FeN4 centers to enhance the ORR catalytic performance. As expected, such a heterostructured FePc-{PW12}@NT electrocatalyst exhibits prominent durability, methanol tolerance, and ORR activity with a high half-wave potential of 0.90 V and a low Tafel slope of 30.9 mV dec−1 in alkaline medium. Besides, the assembled zinc-air battery demonstrates an ultrahigh power density of 280 mW cm−2, excellent charge/discharge ability and long-term stability over 500 h, outperforming that of the commercial Pt/C+IrO2 cathode. This study offers a new strategy to design novel heterostructured catalysts and opens a new avenue to regulate the electrocatalytic performance of phthalocyanine molecules.  相似文献   

5.
Targeted construction of carbon defects near the N dopants is an intriguing but challenging way to boost the electrocatalytic activity of N-doped carbon toward oxygen reduction reaction (ORR). Here, we report a novel site-specific etching strategy that features targeted anchoring of singlet oxygen (1O2) on the N-adjacent atoms to directionally construct topological carbon defects neighboring the N dopants in N-doped carbon (1O2−N/C). This 1O2−N/C exhibits the highest ORR half-wave potential of 0.915 VRHE among all the reported metal-free carbon catalysts. Pyridinic-N bonded with a carbon pentagon of the neighboring topological carbon defects is identified as the primary active configuration, rendering enhanced adsorption of O2, optimized adsorption energy of the ORR intermediates, and a significantly decreased total energy barrier for ORR. This 1O2-induced site-specific etching strategy is also applicable to different precursors, showing a tremendous potential for targeted construction of high-efficiency active sites in carbon-based materials.  相似文献   

6.
The oxygen reduction reaction (ORR) is essential in many life processes and energy conversion systems. It is desirable to design transition metal molecular catalysts inspired by enzymatic oxygen activation/reduction processes as an alternative to noble-metal-Pt-based ORR electrocatalysts, especially in view point of fuel cell commercialization. We have fabricated bio-inspired molecular catalysts electrografted onto multiwalled carbon nanotubes (MWCNTs) in which 5,10,15,20-tetra(pentafluorophenyl) iron porphyrin (iron porphyrin FeF20TPP) is coordinated with covalently electrografted axial ligands varying from thiophene to imidazole on the MWCNTs’ surface. The catalysts’ electrocatalytic activity varied with the axial coordination environment (i. e., S-thiophene, N-imidazole, and O-carboxylate); the imidazole-coordinated catalyst MWCNTs-Im-FeF20TPP exhibited the highest ORR activity among the prepared catalysts. When MWCNT-Im-FeF20TPP was loaded onto the cathode of a zinc−air battery, an open-cell voltage (OCV) of 1.35 V and a maximum power density (Pmax) of 110 mW cm−2 were achieved; this was higher than those of MWCNTs-Thi-FeF20TPP (OCV=1.30 V, Pmax=100 mW cm−2) and MWCNTs-Ox-FeF20TPP (OCV=1.28 V, Pmax=86 mW cm−2) and comparable with a commercial Pt/C catalyst (OCV=1.45 V, Pmax=120 mW cm−2) under similar experimental conditions. This study provides a time-saving method to prepare covalently immobilized molecular electrocatalysts on carbon-based materials with structure–performance correlation that is also applicable to the design of other electrografted catalysts for energy conversion.  相似文献   

7.

In this work, the catalytic activity of carbon nanotubes (CNTs), carbon black (CB), and CNT-CB counter electrodes in the I/I3 reduction reaction is reported and compared with the Pt counter electrode. The fabricated counter electrodes were evaluated in dye-sensitized solar cells (DSSCs). The results indicate that the best cathodes were made from CNT10 (240 μm) and CB with a charge transfer resistance (RCT) of 2.70 Ω, and when the complete device shows 19.83 Ω of internal series resistance (RS), the photovoltaic parameters of these cells were JSC = 10.47 mA cm−2; VOC = 0.70 V; and FF = 57.90, with an efficiency of 4.29%, indicating a better interaction between the CNT10 in the 3D network of the counter electrode, generating a good charge transfer kinetics, in comparison with only CNT10 or CB.

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8.
《Electroanalysis》2018,30(3):436-444
Electrocatalysts perform a key role in increasing efficiency of the oxygen reduction reaction (ORR) and as a result, efforts have been made by the scientific community to develop novel and cheap materials that have the capability to exhibit low ORR overpotentials and allow the reaction to occur via a 4 electron pathway, thereby mimicking as close as possible to traditionally utilised platinum. In that context, two different types of carbon nanodots (CNDs) with amide (CND‐CONH2) and carboxylic (CND‐COOH) surface groups, have herein been fabricated and shown to exhibit excellent electrocatalytic activity towards the ORR in acid and basic media (0.1 M H2SO4 and 0.1 M KOH). CND surface modified carbon screen‐printed electrodes allow for a facile electrode modification and enabling the study of the CNDs electrocatalytic activity towards the ORR. CND‐COOH modified SPEs are found to exhibit improved ORR peak current and reduced overpotential by 21.9 % and 26.3 %, respectively compared to bare/unmodified SPEs. Additionally, 424 μg cm−2 CND‐COOH modified SPEs in oxygenated 0.1 M KOH are found to facilitate the ORR via a near optimal 4 (3.8) electron ORR pathway. The CNDs also exhibited excellent long‐term stability and tolerance with no degradation being observed in the achievable current with the ORR current returning to the baseline level within 100 seconds of exposure to a 1.5 M solution of methanol. In summary, the CND‐COOH could be utilised as a cathodic electrode for PEMFCs offering greater stability than a commercial Pt electrode.  相似文献   

9.
Herein, an ordinary and mass-production approach is reported to synthesize boron (B) and nitrogen (N) co-doped three-dimensional (3D) carbon aerogels (CA) by using glucose and borax as the raw materials by a simple hydrothermal method and then carbonization in NH3 atmosphere. The porous material (BN-CA-900) possesses a large specific surface area (1032 m2 g−1) and high contents of doped pyridinic N and graphitic N. The onset potential (0.91 V vs. reversible hydrogen electrode, RHE), half-wave potential (0.77 V vs. RHE), and current density (5.70 mA cm−2 at 0.2 V vs. RHE) of BN-CA-900 for ORR are similar to those of commercial Pt/C, indicating that BN-CA-900 has a comparable catalytic activity with Pt/C in alkaline media. The number of electron transfer is 3.86–3.99 and the yield of hydrogen peroxide is less than 6.8 %. BN-CA-900 also presents decent catalytic performance in acidic medium. Moreover, the stability and methanol tolerance of BN-CA-900 are superior to commercial Pt/C in both alkaline and acidic media. The prepared BN-CA-900 is a promising candidate that may be applied in other areas, such as the adsorption of pollution, porous conductive electrodes, and lithium-ion batteries.  相似文献   

10.
Developing cost-effective and sustainable acidic water oxidation catalysts requires significant advances in material design and in-depth mechanism understanding for proton exchange membrane water electrolysis. Herein, we developed a single atom regulatory strategy to construct Co−Co dinuclear active sites (DASs) catalysts that atomically dispersed zirconium doped Co9S8/Co3O4 heterostructure. The X-ray absorption fine structure elucidated the incorporation of Zr greatly facilitated the generation of Co−Co DASs layer with stretching of cobalt oxygen bond and S−Co−O heterogeneous grain boundaries interfaces, engineering attractive activity of significantly reduced overpotential of 75 mV at 10 mA cm−2, a breakthrough of 500 mA cm−2 high current density, and water splitting stability of 500 hours in acid, making it one of the best-performing acid-stable OER non-noble metal materials. The optimized catalyst with interatomic Co−Co distance (ca. 2.80 Å) followed oxo-oxo coupling mechanism that involved obvious oxygen bridges on dinuclear Co sites (1,090 cm−1), confirmed by in situ SR-FTIR, XAFS and theoretical simulations. Furthermore, a major breakthrough of 120,000 mA g−1 high mass current density using the first reported noble metal-free cobalt anode catalyst of Co−Co DASs/ZCC in PEM-WE at 2.14 V was recorded.  相似文献   

11.
Layered two‐dimensional (2D) conjugated metal–organic frameworks (MOFs) represent a family of rising electrocatalysts for the oxygen reduction reaction (ORR), due to the controllable architectures, excellent electrical conductivity, and highly exposed well‐defined molecular active sites. Herein, we report a copper phthalocyanine based 2D conjugated MOF with square‐planar cobalt bis(dihydroxy) complexes (Co‐O4) as linkages (PcCu‐O8‐Co) and layer‐stacked structures prepared via solvothermal synthesis. PcCu‐O8‐Co 2D MOF mixed with carbon nanotubes exhibits excellent electrocatalytic ORR activity (E1/2=0.83 V vs. RHE, n=3.93, and jL=5.3 mA cm?2) in alkaline media, which is the record value among the reported intrinsic MOF electrocatalysts. Supported by in situ Raman spectro‐electrochemistry and theoretical modeling as well as contrast catalytic tests, we identified the cobalt nodes as ORR active sites. Furthermore, when employed as a cathode electrocatalyst for zinc–air batteries, PcCu‐O8‐Co delivers a maximum power density of 94 mW cm?2, outperforming the state‐of‐the‐art Pt/C electrocatalysts (78.3 mW cm?2).  相似文献   

12.
The development of alternative electrocatalysts exhibiting high activity in the oxygen reduction reaction (ORR) is vital for the deployment of large-scale clean energy devices, such as fuel cells and zinc–air batteries. N-doped carbon materials offer a promising platform for the design and synthesis of electrocatalysts due to their high ORR activity, high surface area, and tunable porosity. In this study, materials in which MnO nanoparticles are entrapped in N-doped mesoporous carbon (MnO/NC) were developed as electrocatalysts for the ORR, and their performances were evaluated in zinc–air batteries. The obtained carbon materials had large surface area and high electrocatalytic activity toward the ORR. The carbon compounds were fabricated by using NaCl as template in a one-pot process, which significantly simplifies the procedure for preparing mesoporous carbon materials and in turn reduces the total cost. A primary zinc–air battery based on this material exhibits an open-circuit voltage of 1.49 V, which is higher than that of conventional zinc–air batteries with Pt/C (Pt/C cell) as ORR catalyst (1.41 V). The assembled zinc–air battery delivered a peak power density of 168 mW cm−2 at a current density of about 200 mA cm−2, which is higher than that of an equivalent Pt/C cell (151 mW cm−2 at a current density of ca. 200 mA cm−2). The electrocatalytic data revealed that MnO/NC is a promising nonprecious-metal ORR catalyst for practical applications in metal–air batteries.  相似文献   

13.
《Electroanalysis》2006,18(16):1564-1571
The work details the electrocatalysis of oxygen reduction reaction (ORR) in 0.5 M H2SO4 medium on a modified electrode containing a film of polyaniline (PANI) grafted multi‐wall carbon nanotube (MWNT) over the surface of glassy carbon electrode. We have fabricated a novel modified electrode in which conducting polymer is present as connected unit to MWNT. The GC/PANI‐g‐MWNT modified electrode (ME) is fabricated by electrochemical polymerization of a mixture of amine functionalized MWNT and aniline with GC as working electrode. Cyclic voltammetry and amperometry are used to demonstrate the electrocatalytic activity of the GC/PANI‐g‐MWNT‐ME. The GC/PANI‐g‐MWNT‐ME exhibits remarkable electrocatalytic activity for ORR. A more positive onset potential and higher catalytic current for ORR are striking features of GC/PANI‐g‐MWNT‐ME. Rapid and high sensitivity of GC/PANI‐g‐MWNT‐ME to ORR are evident from the higher rate constant (7.92×102 M?1 s?1) value for the reduction process. Double potential chronoamperometry and rotating disk and rotating ring‐disk electrode (RRDE) experiments are employed to investigate the kinetic parameters of ORR at this electrode. Results from RDE and RRDE voltammetry demonstrate the involvement of two electron transfer in oxygen reduction to form hydrogen peroxide in acidic media.  相似文献   

14.
Design and synthesis of low-cost and efficient bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Zn-air batteries are essential and challenging. We report a facile method to synthesize heterostructure carbon consisting of graphitic and amorphous carbon derived from the agricultural waste of red bean pods. The heterostructure carbon possesses a large surface area of 625.5 m2 g−1, showing ORR onset potential of 0.89 V vs. RHE and OER overpotential of 470 mV at 5 mA cm−2. Introducing hollow FeCo nanoparticles and nitrogen dopant improves the bifunctional catalytic activity of the carbon, delivering ORR onset potential of 0.93 V vs. RHE and OER overpotential of 360 mV. Electron energy-loss spectroscopy (EELS) O K-edge map suggests the presence of localized oxygen on the FeCo nanoparticles, suggesting the oxidation of the nanoparticles. Zn-air battery with these carbon-based catalysts exhibits a peak power density as high as 116.2 mW cm−2 and stable cycling performance over 210 discharge/charge cycles. This work contributes to the advancement of bifunctional oxygen electrocatalysts while converting agricultural waste into value-added material.  相似文献   

15.
An dual electronic and architectural engineering strategy is a good way to rationally design earth-abundant and highly efficient electrocatalysts of the oxygen evolution reaction (OER) for sustainable hydrogen-based energy devices. Here, a Ce-doped Co9S8 core–shell nanoneedle array (Ce−Co9S8@CC) supported on a carbon cloth has been designed and developed to accelerate the sluggish kinetics of the OER. Profiting from valance alternative Ce doping, a fine core–shell structure and vertically aligned nanoneedle arrayed architecture, Ce−Co9S8@CC integrates modulated electronic structure, highly exposed active sites, and multidimensional mass diffusion channels; together, these afford a favorable catalyzed OER. Ce−Co9S8@CC exhibits remarkable performance in the OER in an alkaline medium, where the overpotential requires only 242 mV to deliver a current density of 10 mA cm−2 for the OER; this is 70 mV superior to that of Ce-free Co9S8 catalyst and other counterparts. Good stability and impressive selectivity (nearly 100 % Faradic efficiency) are also demonstrated. When integrated into a two-electrode OER//HER electrolyzer, the as-prepared Ce−Co9S8@CC displays a low operation potential of 1.54 V at 10 mA cm−2 and long-term stability, thus demonstrating great potential for economical water electrolysis.  相似文献   

16.
赖渊  周德璧  胡剑文  崔莉莉 《化学学报》2008,66(9):1015-1020
碳黑经过酸处理后再加入醋酸钴经氨气900 ℃热处理后, 以其制备的气体扩散电极在6 mol•L―1 KOH溶液中对氧还原反应(ORR)的电催化性能得到大大提高. XRD物相分析表明: 碳粉中加入醋酸钴经氨气热处理生成了氮化钴(Co5.47N). 通过极化曲线和交流阻抗方法对制备的气体扩散电极在空气中的性能进行了研究. 室温时在-0.2 V (vs. Hg/HgO)电位下, 未经处理的碳电极对氧还原基本没有电流产生; 用酸处理后的碳电极在空气中的电流密度提高到57 mA•cm―2; 而Co-N/C复合电极在同样条件下电流密度可达170 mA•cm―2, 交流阻抗显示氮化物的生成减小了氧还原反应的阻抗, 增强了对氧还原反应的电催化作用.  相似文献   

17.
Metal-free covalent organic frameworks (COFs) have been employed to catalyze the oxygen reduction reaction (ORR). To achieve high activity and selectivity, various building blocks containing heteroatoms and groups linked by imine bonds were used to create catalytic COFs. However, the roles of linkages of COFs in ORR have not been investigated. In this work, the catalytic linkage engineering has been employed to modulate the catalytic behaviors. To create single catalytic sites while avoiding other possible catalytic sites, we synthesized COFs from benzene units linked by various bonds, such as imine, amide, azine, and oxazole bonds. Among these COFs, the oxazole-linkage in COFs enables to catalyze the ORR with the highest activity, which achieved a half-wave potential of 0.75 V and a limited current density of 5.5 mA cm−2. Moreover, the oxazole-linked COF achieved a conversion frequency (TOF) value of 0.0133 S−1, which were 1.9, 1.3, and 7.4-times that of azine-, amide- and imine-COFs, respectively. The theoretical calculation showed that the carbon atoms in oxazole linkages facilitated the formation of OOH* and promoted protonation of O* to form the OH*, thus advancing the catalytic activity. This work guides us on which linkages in COFs are suitable for ORR.  相似文献   

18.
A mesoporous zirconia modified carbon paste electrode was developed for electrochemical investigations of methyl parathion (MP, Phen‐NO2). The significant increase of the peak currents and the improvement of the redox peak potential indicate that mesoporous zirconia facilitates the electronic transfer of MP. The oxidation peak current was proportional to the MP concentration in the range from 1.0×10−8 to 1.0×10−5 mol L−1 with a detection limit of 4.6×10−9 mol L−1 (S/N=3) after accumulation under open‐circuit for 210 s. The proposed method was successfully applied to the determination of MP in apple samples.  相似文献   

19.
Understanding the nature of single-atom catalytic sites and identifying their spectroscopic fingerprints are essential prerequisites for the rational design of target catalysts. Here, we apply correlated in situ X-ray absorption and infrared spectroscopy to probe the edge-site-specific chemistry of Co−N−C electrocatalyst during the oxygen reduction reaction (ORR) operation. The unique edge-hosted architecture affords single-atom Co site remarkable structural flexibility with adapted dynamic oxo adsorption and valence state shuttling between Co(2−δ)+ and Co2+, in contrast to the rigid in-plane embedded Co1−Nx counterpart. Theoretical calculations demonstrate that the synergistic interplay of in situ reconstructed Co1−N2-oxo with peripheral oxygen groups gives a rise to the near-optimal adsorption of *OOH intermediate and substantially increases the activation barrier for its dissociation, accounting for a robust acidic ORR activity and 2e selectivity for H2O2 production.  相似文献   

20.
The development of cost-effective and durable oxygen electrocatalysts remains highly critical but challenging for energy conversion and storage devices. Herein, a novel FeNi alloy nanoparticle core encapsulated in carbon shells supported on a N-enriched graphene-like carbon matrix (denoted as FeNi@C/NG) was constructed by facile pyrolyzing the mixture of metal salts, glucose, and dicyandiamide. The in situ pyrolysis of dicyandiamide in the presence of glucose plays a significant effect on the fabrication of the porous FeNi@C/NG with a high content of doped N and large specific surface area. The optimized FeNi@C/NG catalyst displays not only a superior catalytic performance for the oxygen reduction reaction (ORR, with an onset potential of 1.0 V and half-wave potential of 0.84 V) and oxygen evolution reaction (OER, the potential at 10 mA cm−2 is 1.66 V) simultaneously in alkaline, but also outstanding long-term cycling durability. The excellent bifunctional ORR/OER electrocatalytic performance is ascribed to the synergism of the carbon shell and FeNi alloy core together with the high-content of nitrogen doped on the large specific surface area graphene-like carbon.  相似文献   

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