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1.
Two‐dimensional conjugated aromatic networks (CAN) with ultra‐thin conjugated layers (ca. 3.5 nm) and high single‐metal‐atom‐site density (mass content of 10.7 wt %, and 0.73 metal atoms per nm2) are prepared via a facile pyrolysis‐free route involving a one‐step ball milling of the solid‐phase‐synthesized polyphthalocyanine. These materials display outstanding oxygen reduction reaction (ORR) mass activity of 47 mA mgcat.?1 represents 1.3‐ and 6.4‐fold enhancements compared to Pt and Pt/C in benchmark Pt/C, respectively. Moreover, the primary Zn‐air batteries constructed with CAN as an air electrode demonstrate a mass/volume power density of 880 W gcat.?1/615 W cmcat.?3 and stable long‐term operation for 100 h. This strategy offers a new way to design high‐performance electrocatalysts with atomic precision for use in other energy‐storage and conversion applications.  相似文献   

2.
Cost‐effective and high‐performance electrocatalysts for oxygen reduction reactions (ORR) are needed for many energy storage and conversion devices. Here, we demonstrate that whey powder, a major by‐product in the dairy industry, can be used as a sustainable precursor to produce heteroatom doped carbon electrocatalysts for ORR. Rich N and S compounds in whey powders can generate abundant catalytic active sites. However, these sites are not easily accessible by reactants of ORR. A dual‐template method was used to create a hierarchically and interconnected porous structure with micropores created by ZnCl2 and large mesopores generated by fumed SiO2 particles. At the optimum mass ratio of whey power: ZnCl2 : SiO2 at 1 : 3 : 0.8, the resulting carbon material has a large specific surface area close to 2000 m2 g?1, containing 4.6 at.% of N with 39.7% as pyridinic N. This carbon material shows superior electrocatalytic activity for ORR, with an electron transfer number of 3.88 and a large kinetic limiting current density of 45.40 mA cm?2. They were employed as ORR catalysts to assemble primary zinc‐air batteries, which deliver a power density of 84.1 mW cm?2 and a specific capacity of 779.5 mAh g?1, outperforming batteries constructed using a commercial Pt/C catalyst. Our findings open new opportunities to use an abundant biomaterial, whey powder, to create high‐value‐added carbon electrocatalysts for emerging energy applications.  相似文献   

3.
Developing cost‐effective electrocatalysts for the oxygen reduction reaction (ORR) is a prerequisite for broad market penetration of low‐temperature fuel cells. A major barrier stems from the poisoning of surface sites by nonreactive oxygenated species and the sluggish ORR kinetics on the Pt catalysts. Herein we report a facile approach to accelerating ORR kinetics by using a hydrophobic ionic liquid (IL), which protects Pt sites from surface oxidation, making the IL‐modified Pt intrinsically more active than its unmodified counterpart. The mass activity of the catalyst is increased by three times to 1.01 A mg?1Pt@0.9 V, representing a new record for pure Pt catalysts. The enhanced performance of the IL‐modified catalyst can be stabilized after 30 000 cycles. We anticipate these results will form the basis for an unprecedented perspective in the development of high‐performing electrocatalysts for fuel‐cell applications.  相似文献   

4.
Three‐dimensional porous platinum (Ptpor) films are prepared based on Pt electrodeposition on polyaniline (PANI) modified electrodes followed by selective dissolution of PANI with HNO3. Electrochemical quartz crystal microbalance data suggest that the PANI‐H2PtCl6 interaction involves redox and coordination reactions, depending on the working potential. The Ptpor shows better electrocatalytic performance than the Pt/PANI and conventionally electrodeposited Pt. The Ptpor modified glassy carbon electrode (GCE) can electrocatalyze the oxidation of H2O2 with a sensitivity of 414 µA cm?2 mM?1 and a detection limit of 9 nM, and the chitosan‐glucose oxidase/Ptpor/GCE can sense glucose with a sensitivity of 93.4 µA cm?2 mM?1.  相似文献   

5.
The development of low‐cost, efficient, and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. Herein, we made a highly reactive and stable isolated single‐atom Fe/N‐doped porous carbon (ISA Fe/CN) catalyst with Fe loading up to 2.16 wt %. The catalyst showed excellent ORR performance with a half‐wave potential (E 1/2) of 0.900 V, which outperformed commercial Pt/C and most non‐precious‐metal catalysts reported to date. Besides exceptionally high kinetic current density (J k) of 37.83 mV cm−2 at 0.85 V, it also had a good methanol tolerance and outstanding stability. Experiments demonstrated that maintaining the Fe as isolated atoms and incorporating nitrogen was essential to deliver the high performance. First principle calculations further attributed the high reactivity to the high efficiency of the single Fe atoms in transporting electrons to the adsorbed OH species.  相似文献   

6.
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   

7.
The high cost of platinum electrocatalysts for the oxygen reduction reaction (ORR) has hindered the commercialization of fuel cells. An effective support can reduce the usage of Pt and improve the reactivity of Pt through synergistic effects. Herein, the vanadium nitride/graphitic carbon (VN/GC) nanocomposites, which act as an enhanced carrier of Pt nanoparticles (NPs) towards ORR, have been synthesized for the first time. In the synthesis, the VN/GC composite could be obtained by introducing VO3? and [Fe(CN)6]4? ions into the polyacrylic weak‐acid anion‐exchanged resin (PWAR) through an in‐situ anion‐exchanged route, followed by carbonization and a subsequent nitridation process. After loading only 10 % Pt NPs, the resulting Pt‐VN/GC catalyst demonstrates a more positive onset potential (1.01 V), higher mass activity (137.2 mA mg?1), and better cyclic stability (99 % electrochemical active surface area (ECSA) retention after 2000 cycles) towards ORR than the commercial 20 % Pt/C. Importantly, the Pt‐VN/GC catalyst mainly exhibits a 4 e?‐transfer mechanism and a low yield of peroxide species, suggesting its potential application as a low‐cost and highly efficient ORR catalyst in fuel cells.  相似文献   

8.
It remains a big challenge to remarkably improve both oxygen reduction reaction (ORR) activity and long‐term durability of Pt?M bimetal electrocatalysts simultaneously in the harsh cathode environment toward widespread commercialization of polymer electrolyte fuel cells (PEFC). In this account we found double‐promotional effects of carbon micro coil (CMC) support on ORR performance and durability of octahedral Pt3Ni nanoparticles (Oh Pt3Ni/CMC). The Oh Pt3Ni/CMC displayed remarkable improvements of mass activity (MA; 13.6 and 34.1 times) and surface specific activity (SA; 31.3 and 37.0 times) compared to those of benchmark Pt/C (TEC10E20E) and Pt/C (TEC10E50E‐HT), respectively. Notably, the Oh Pt3Ni/CMC revealed a negligible MA loss after 50,000 triangular‐wave 1.0–1.5 VRHE (startup/shutdown) load cycles, contrasted to MA losses of 40 % (TEC10E20E) and 21.5 % (TEC10E50E‐HT) by only 10,000 load cycles. It was also found that the SA increased exponentially with the decrease in the CO stripping peak potential in a series of Pt?M/carbon (M: Ni and Co), which predicts a maximum SA at the curve asymptote. Key factors for simultaneous improvements of performance and durability of core‐shell Pt3Ni/carbon electrocatalysts toward superior PEFC is also discussed.  相似文献   

9.
Single metal atoms immobilized on a carbon substrate are of great potential for enhancing the catalytic activities for oxygen reduction and methanol oxidation reactions(ORR/MOR) owing to the maximized atom utilization. Herein, single copper atoms(SCAs) are loaded on macro-porous nitrogen-doped carbon(Cu-NC) derived from zeolitic imidazolate framework-8(ZIF-8), which are used as catalysts for ORR and Pt-supports for MOR. For ORR, the catalyst marked as Cu-NC-3 exhibits a higher peak potential of ...  相似文献   

10.
Fe‐Co‐N‐C electrocatalysts have proven superior to their counterparts (e.g. Fe‐N‐C or Co‐N‐C) for the oxygen reduction reaction (ORR). Herein, we report on a unique strategy to prepare Fe‐Co‐N‐C?x (x refers to the pyrolysis temperature) electrocatalysts which involves anion‐exchange of [Fe(CN)6]3? into a cationic CoII‐based metal‐organic framework precursor prior to heat treatment. Fe‐Co‐N‐C‐900 exhibits an optimal ORR catalytic performance in an alkaline electrolyte with an onset potential (Eonset: 0.97 V) and half‐wave potential (E1/2: 0.86 V) comparable to that of commercial Pt/C (Eonset=1.02 V; E1/2=0.88 V), which outperforms the corresponding Co‐N‐C‐900 sample (Eonset=0.92 V; E1/2=0.84 V) derived from the same MOF precursor without anion‐exchange modification. This is the first example of Fe‐Co‐N‐C electrocatalysts fabricated from a cationic CoII‐based MOF precursor that dopes the Fe element via anion‐exchange, and our current work provides a new entrance towards MOF‐derived transition‐metal (e.g. Fe or Co) and nitrogen‐codoped carbon electrocatalysts with excellent ORR activity.  相似文献   

11.
The present study demonstrates the use of few‐layer borocarbonitride nanosheets synthesized by a simple method as non‐platinum cathode catalysts for the oxygen reduction reaction (ORR) in alkaline medium. Composition‐dependent ORR activity is observed and the best performance was found when the composition was carbon‐rich. Mechanistic aspects reveal that ORR follows the 4 e? pathway with kinetic parameters comparable to those of the commercial Pt/C catalyst. Excellent methanol tolerance is observed with the BCN nanosheets unlike with Pt/C.  相似文献   

12.
The replacement of platinum with non‐precious‐metal electrocatalysts with high efficiency and superior stability for the hydrogen‐evolution reaction (HER) remains a great challenge. Herein, we report the one‐step synthesis of uniform, ultrafine molybdenum carbide (Mo2C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo2C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1–3 layers) showed superior HER activity in acidic media, with a very low onset potential of ?6 mV, a small Tafel slope of 41 mV dec?1, and a large exchange current density of 0.179 mA cm?2, as well as good stability during operation for 12 h. These excellent properties are similar to those of state‐of‐the‐art 20 % Pt/C and make the catalyst one of the most active acid‐stable electrocatalysts ever reported for HER.  相似文献   

13.
The anchoring of small‐sized WN (tungsten nitride) nanoparticles (NPs) with good dispersion on carbon nanotubes (CNTs) offers an effective means of obtaining promising materials for use in electrocatalysis. Herein, an effective method based on grinding treatment followed by a nitridation process is proposed to realize this goal. In the synthesis, a solution containing H4[SiO4(W3O9)4] (SiW12) and CNTs modified with polyethylenimine (PEI‐CNTs) was ground to dryness. Small‐sized WN NPs were anchored onto the CNTs with good dispersion after calcination under NH3. Under hydrothermal assembly conditions (absence of grinding), WN particles of larger size and with inferior dispersion were obtained, demonstrating the important role of the grinding process. The benefit of the small‐sized WN has been demonstrated by using WN/CNTs as a support for Pt to catalyze the methanol electro‐oxidation reaction. The mass activity of Pt‐WN/CNTs‐G‐70 (where G denotes the grinding treatment, and 70 is the loading amount (%) of WN in the WN/CNTs) was evaluated as about 817 mA mg?1Pt, better that those of commercial Pt/C (340 mA mg?1Pt) and Pt/CNTs (162 mA mg?1Pt). The Pt‐WN/CNTs‐G also displayed good CO tolerance. In contrast, Pt‐WN/CNTs prepared without the grinding process displayed an activity of 344 mA mg?1Pt, verifying the key role of grinding treatment in the preparation of WN/CNTs with good co‐catalytic effect.  相似文献   

14.
The sluggish kinetics of the oxygen reduction reaction (ORR) at the cathodes of fuel cells significantly hampers fuel cell performance. Therefore, the development of high‐performance, non‐precious‐metal catalysts as alternatives to noble metal Pt‐based ORR electrocatalysts is highly desirable for the large‐scale commercialization of fuel cells. TiO2‐grafted copper complexes deposited on multiwalled carbon nanotubes (CNTs) form stable and efficient electrocatalysts for the ORR. The optimized catalyst composite CNTs@TiO2–ZA–[Cu(phen)(BTC)] shows surprisingly high selectivity for the 4 e? reduction of O2 to water (approximately 97 %) in alkaline solution with an onset potential of 0.988 V vs. RHE, and demonstrates superior stability and excellent tolerance for the methanol crossover effect in comparison to a commercial Pt/C catalyst. The copper complexes were grafted onto the surface of TiO2 through coordination of an imidazole‐containing ligand, zoledronic acid (ZA), which binds to TiO2 through its bis‐phosphoric acid anchoring group. Rational optimization of the copper catalyst’s ORR performance was achieved by using an electron‐deficient ligand, 5‐nitro‐1,10‐phenanthroline (phen), and bridging benzene‐1,3,5‐tricarboxylate (BTC). This facile approach to the assembly of copper catalysts on TiO2 with rationally tuned ORR activity will have significant implications for the development of high‐performance, non‐precious‐metal ORR catalysts.  相似文献   

15.
Even though transition‐metal phosphides (TMPs) have been developed as promising alternatives to Pt catalyst for the hydrogen evolution reaction (HER), further improvement of their performance requires fine regulation of the TMP sites related to their specific electronic structure. Herein, for the first time, boron (B)‐modulated electrocatalytic characteristics in CoP anchored on the carbon nanotubes (B‐CoP/CNT) with impressive HER activities over a wide pH range are reported. The HER performance surpasses commercial Pt/C in both neutral and alkaline media at large current density (>100 mA cm?2). A combined experimental and theoretical study identified that the B dopant could reform the local electronic configuration and atomic arrangement of bonded Co and adjacent P atoms, enhance the electrons’ delocalization capacity of Co atoms for high electrical conductivity, and optimize the free energy of H adsorption and H2 desorption on the active sites for better HER kinetics.  相似文献   

16.
The title compound, catena‐poly[[[bis(ethylenediamine‐κ2N,N′)platinum(II)]‐ μ‐chlorido‐[bis(ethylenediamine)platinum(IV)]‐μ‐chlorido] tetrakis{4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate} dihydrate], {[PtIIPtIVCl2(C2H8N2)4](HOC6H4N=NC6H4SO3)4·2H2O}n, has a linear chain structure composed of square‐planar [Pt(en)2]2+ (en is ethylenediamine) and elongated octahedral trans‐[PtCl2(en)2]2+ cations stacked alternately, bridged by Cl atoms, along the b axis. The Pt atoms are located on an inversion centre, while the Cl atoms are disordered over two sites and form a zigzag ...Cl—PtIV—Cl...PtII... chain, with a PtIV—Cl bond length of 2.3140 (14) Å, an interatomic PtII...Cl distance of 3.5969 (15) Å and a PtIV—Cl...PtII angle of 170.66 (6)°. The structural parameter indicating the mixed‐valence state of the Pt atom, expressed by δ = (PtIV—Cl)/(PtII...Cl), is 0.643.  相似文献   

17.
Single‐atom catalysts are promising platforms for heterogeneous catalysis, especially for clean energy conversion, storage, and utilization. Although great efforts have been made to examine the bonding and oxidation state of single‐atom catalysts before and/or after catalytic reactions, when information about dynamic evolution is not sufficient, the underlying mechanisms are often overlooked. Herein, we report the direct observation of the charge transfer and bond evolution of a single‐atom Pt/C3N4 catalyst in photocatalytic water splitting by synchronous illumination X‐ray photoelectron spectroscopy. Specifically, under light excitation, we observed Pt?N bond cleavage to form a Pt0 species and the corresponding C=N bond reconstruction; these features could not be detected on the metallic platinum‐decorated C3N4 catalyst. As expected, H2 production activity (14.7 mmol h?1 g?1) was enhanced significantly with the single‐atom Pt/C3N4 catalyst as compared to metallic Pt‐C3N4 (0.74 mmol h?1 g?1).  相似文献   

18.
It is highly desirable but challenging to optimize the structure of photocatalysts at the atomic scale to facilitate the separation of electron–hole pairs for enhanced performance. Now, a highly efficient photocatalyst is formed by assembling single Pt atoms on a defective TiO2 support (Pt1/def‐TiO2). Apart from being proton reduction sites, single Pt atoms promote the neighboring TiO2 units to generate surface oxygen vacancies and form a Pt‐O‐Ti3+ atomic interface. Experimental results and density functional theory calculations demonstrate that the Pt‐O‐Ti3+ atomic interface effectively facilitates photogenerated electrons to transfer from Ti3+ defective sites to single Pt atoms, thereby enhancing the separation of electron–hole pairs. This unique structure makes Pt1/def‐TiO2 exhibit a record‐level photocatalytic hydrogen production performance with an unexpectedly high turnover frequency of 51423 h?1, exceeding the Pt nanoparticle supported TiO2 catalyst by a factor of 591.  相似文献   

19.
The bis(diphenylphosphino)methane (dppm)‐bridged dinuclear cycloplatinated complex {[Pt(L)]2(μ‐dppm)}2+ (Pt2 ? dppm; HL: 2‐phenyl‐6‐(1H‐pyrazol‐3‐yl)‐pyridine) demonstrates interesting reversible “pivot‐hinge”‐like intramolecular motions in response to the protonation/deprotonation of L. In its protonated “closed” configuration, the two platinum(II) centers are held in position by intramolecular d8–d8 Pt–Pt interaction. In its deprotonated “open” configuration, such Pt–Pt interaction is cleaved. To further understand the mechanism behind this hingelike motion, an analogous dinuclear cycloplatinated complex, {[Pt(L)]2(μ‐dchpm)}2+ (Pt2 ? dchpm) with bis(dicyclohexylphosphino)methane (dchpm) as the bridging ligand, was synthesized. From its protonation/deprotonation responses, it was revealed that aromatic π–π interactions between the phenyl moieties of the μ‐dppm and the deprotonated pyrazolyl rings of L was essential to the reversible cleavage of the intramolecular Pt–Pt interaction in Pt2 ? dppm. In the case of Pt2 ? dchpm, spectroscopic and spectrofluorometric titrations as well as X‐ray crystallography indicated that the distance between the two platinum(II) centers shrank upon deprotonation, thus causing a redshift in its room‐temperature triplet metal–metal‐to‐ligand charge‐transfer emission from 614 to 625 nm. Ab initio calculations revealed the presence of intramolecular hydrogen bonding between the deprotonated and negatively charged 1‐pyrazolyl‐N moiety and the methylene CH and phenyl C–H of the μ‐dppm. The “open” configuration of the deprotonated Pt2 ? dppm was estimated to be 19 kcal mol?1 more stable than its alternative “closed” configuration. On the other hand, the open configuration of the deprotonated Pt2 ? dchpm was 6 kcal mol?1 less stable than its alternative closed configuration.  相似文献   

20.
A new one‐dimensional platinum mixed‐valence complex with nonhalogen bridging ligands, namely catena‐poly[[[bis(ethane‐1,2‐diamine‐κ2N,N′)platinum(II)]‐μ‐thiocyanato‐κ2S:S‐[bis(ethane‐1,2‐diamine‐κ2N,N′)platinum(IV)]‐μ‐thiocyanato‐κ2S:S] tetrakis(perchlorate)], {[Pt2(SCN)2(C2H8N2)4](ClO4)4}n, has been isolated. The PtII and PtIV atoms are located on centres of inversion and are stacked alternately, linked by the S atoms of the thiocyanate ligands, forming an infinite one‐dimensional chain. The PtIV—S and PtII...S distances are 2.3933 (10) and 3.4705 (10) Å, respectively, and the PtIV—S...PtII angle is 171.97 (4)°. The introduction of nonhalogen atoms as bridging ligands in this complex extends the chemical modifications possible for controlling the amplitude of the charge‐density wave (CDW) state in one‐dimensional mixed‐valence complexes. The structure of a discrete PtIV thiocyanate compound, bis(ethane‐1,2‐diamine‐κ2N,N′)bis(thiocyanato‐κS)platinum(IV) bis(perchlorate) 1.5‐hydrate, [Pt(SCN)2(C4H8N2)2](ClO4)2·1.5H2O, has monoclinic (C2) symmetry. Two S‐bound thiocyanate ligands are located in trans positions, with an S—Pt—S angle of 177.56 (3)°.  相似文献   

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