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1.
Xingbo Ge Luyang Chen Jianli Kang Takeshi Fujita Akihiko Hirata Wei Zhang Jianhua Jiang Mingwei Chen 《Advanced functional materials》2013,23(33):4156-4162
Composition‐controlled fabrication of bimetallic catalysts is of significance in electrochemical energy conversion and storage. A novel nanoporous Pt‐Cu bimetallic catalyst with a Pt skin and a Pt‐Cu core, fabricated by electrochemically dealloying a bulk Pt‐Cu binary alloy using a potential‐controlled approach, is reported. The Pt/Cu ratio of the dealloyed nanoporous catalyst can be readily adjusted in a wide composition range by only controlling dealloying potential. The electro‐catalytic performance of the nanoporous Pt‐Cu catalyst shows evident dependence on Pt/Cu ratio although the surfaces of all the nanoporous catalysts are characterized to be covered by pure Pt. With optimal compositions, the dealloyed nanoporous Pt‐Cu catalyst possesses enhanced electrocatalytic activities toward oxygen reduction reaction and formic acid oxidation in comparison with the commercial Pt/C catalyst. 相似文献
2.
J. J. Yu X. P. Wang L. D. Li Z. P. Hao Z. P. Xu G. Q. Lu 《Advanced functional materials》2007,17(17):3598-3606
In this paper, novel multi‐functional mixed‐oxide catalysts have been rationally designed and developed for the effective abatement of NOx. CaxCo3 – xAl hydrotalcite‐like compounds (where x = 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) are first synthesized by co‐precipitation and calcined at 800 °C for 4 h in air to derive the mixed oxides. The resultant mixed oxides are generally of spinel phase, where the CaO phase is segregated when x ≥ 2.5. It has subsequently been found that the derived oxides are catalytically multi‐functional for NOx decomposition, capture, and reduction. For example, the mixed Ca2Co1Al1‐oxide can decompose 55 % NO at 300 °C in 8 % oxygen, completely trap NO for 750 s, and capture 12.88 and 18.06 mg g–1 NO within 30 and 60 min, respectively. The catalytic activities of the Ca2Co1Al1‐oxide catalyst have been further improved by incorporating La to form a quaternary catalyst Ca2Co1La0.1Al0.9‐oxide. This catalyst significantly enhances the NO decomposition to 75 %, extends the complete trapping time to 1100 s, and captures more NO at 300 °C in 8 % O2 (19.02 mg g–1 NO within 60 min). The in‐situ IR spectra of the catalysts with adsorbed NO indicates that the major nitrogen species formed on the catalysts are various kinds of nitrites and nitrates, which can be readily reduced by H2 within 6 min at 350 °C. Therefore, the excellent catalytic activity of layered double hydroxide (LDH)‐based mixed oxides for NO decomposition, storage, and reduction can be achieved by the elegant combination of normal transition metals. 相似文献
3.
Recent advances in oxygen reduction reaction catalysis for proton exchange membrane fuel cells (PEMFCs) include i) the use of electrochemical dealloying to produce high surface area and sometimes nanoporous catalysts with a Pt‐enriched outer surface, and ii) the observation that oxygen reduction in nanoporous materials can be potentially enhanced by confinement effects, particularly if the chemical environment within the pores can bias the reaction toward completion. Here, these advances are combined by incorporating a hydrophobic, protic ionic liquid, [MTBD][beti], into the pores of high surface‐area NiPt alloy nanoporous nanoparticles (np‐NiPt/C + [MTBD][beti]). The high O2 solubility of the [MTBD][beti], in conjunction with the confined environment within the pores, biases reactant O2 toward the catalytic surface, consistent with an increased residence time and enhanced attempt frequencies, resulting in improved reaction kinetics. Half‐cell measurements show the np‐NiPt/C+[MTBD][beti] encapsulated catalyst to be nearly an order of magnitude more active than commercial Pt/C, a result that is directly translated into operational PEMFCs. 相似文献
4.
Luyang Chen Hai Guo Takeshi Fujita Akihiko Hirata Wei Zhang Akihisa Inoue Mingwei Chen 《Advanced functional materials》2011,21(22):4364-4370
A nanoporous PdNi (np‐PdNi) bimetallic catalyst fabricated by electrochemically dealloying a Pd20Ni80 alloy in an acid solution is reported. Residual Ni in the nanoporous alloy can be controlled by tuning dealloying potentials and the electrocatalysis of the np‐PdNi shows evident dependence on Ni concentrations. With ~9 at.% Ni, the np‐PdNi bimetallic catalyst presents superior electrocatalytic performances in methanol and formic acid electro‐oxidation as well as oxygen reduction in comparison with commercial Pd/C and nanoporous Pd (np‐Pd). The excellent electrocatalytic properties of the dealloyed np‐PdNi bimetallic catalyst appear to arise from the combined effect of unique bicontinuous nanoporosity and bimetallic synergistic action. 相似文献
5.
Yueming Tan Chaofa Xu Guangxu Chen Xiaoliang Fang Nanfeng Zheng Qingji Xie 《Advanced functional materials》2012,22(21):4584-4591
Developing low‐cost non‐precious metal catalysts for high‐performance oxygen reduction reaction (ORR) is highly desirable. Here a facile, in situ template synthesis of a MnO‐containing mesoporous nitrogen‐doped carbon (m‐N‐C) nanocomposite and its high electrocatalytic activity for a four‐electron ORR in alkaline solution are reported. The synthesis of the MnO‐m‐N‐C nanocomposite involves one‐pot hydrothermal synthesis of Mn3O4@polyaniline core/shell nanoparticles from a mixture containing aniline, Mn(NO3)2, and KMnO4, followed by heat treatment to produce N‐doped ultrathin graphitic carbon coated MnO hybrids and partial acid leaching of MnO. The as‐prepared MnO‐m‐N‐C composite catalyst exhibits high electrocatalytic activity and dominant four‐electron oxygen reduction pathway in 0.1 M KOH aqueous solution due to the synergetic effect between MnO and m‐N‐C. The pristine MnO shows little electrocatalytic activity and m‐N‐C alone exhibits a dominant two‐electron process for ORR. The MnO‐m‐N‐C composite catalyst also exhibits superior stability and methanol tolerance to a commercial Pt/C catalyst, making the composite a promising cathode catalyst for alkaline methanol fuel cell applications. The synergetic effect between MnO and N‐doped carbon described provides a new route to design advanced catalysts for energy conversion. 相似文献
6.
Guangwei He Shiqi Huang Luis Francisco Villalobos Mohammad Tohidi Vahdat Michael D. Guiver Jing Zhao Wan‐Chi Lee Mounir Mensi Kumar Varoon Agrawal 《Advanced functional materials》2020,30(39)
High‐flux nanoporous single‐layer graphene membranes are highly promising for energy‐efficient gas separation. Herein, in the context of carbon capture, a remarkable enhancement in the CO2 selectivity is demonstrated by uniquely masking nanoporous single‐layer graphene with polymer with intrinsic microporosity (PIM‐1). In the process, a major bottleneck of the state‐of‐the‐art pore‐incorporation techniques in graphene has been overcome, where in addition to the molecular sieving nanopores, larger nonselective nanopores are also incorporated, which so far, has restricted the realization of CO2‐sieving from graphene membranes. Overall, much higher CO2/N2 selectivity (33) is achieved from the composite film than that from the standalone nanoporous graphene (NG) (10) and the PIM‐1 membranes (15), crossing the selectivity target (20) for postcombustion carbon capture. The selectivity enhancement is explained by an analytical gas transport model for NG, which shows that the transport of the stronger‐adsorbing CO2 is dominated by the adsorbed phase transport pathway whereas the transport of N2 benefits significantly from the direct gas‐phase transport pathway. Further, slow positron annihilation Doppler broadening spectroscopy reveals that the interactions with graphene reduce the free volume of interfacial PIM‐1 chains which is expected to contribute to the selectivity. Overall, this approach brings graphene membrane a step closer to industrial deployment. 相似文献
7.
Nitrogen‐Doped Nanoporous Carbon/Graphene Nano‐Sandwiches: Synthesis and Application for Efficient Oxygen Reduction
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Jing Wei Yaoxin Hu Yan Liang Biao Kong Jin Zhang Jingchao Song Qiaoliang Bao George P. Simon San Ping Jiang Huanting Wang 《Advanced functional materials》2015,25(36):5768-5777
A zeolitic‐imidazolate‐framework (ZIF) nanocrystal layer‐protected carbonization route is developed to prepare N‐doped nanoporous carbon/graphene nano‐sandwiches. The ZIF/graphene oxide/ZIF sandwich‐like structure with ultrasmall ZIF nanocrystals (i.e., ≈20 nm) fully covering the graphene oxide (GO) is prepared via a homogenous nucleation followed by a uniform deposition and confined growth process. The uniform coating of ZIF nanocrystals on the GO layer can effectively inhibit the agglomeration of GO during high‐temperature treatment (800 °C). After carbonization and acid etching, N‐doped nanoporous carbon/graphene nanosheets are formed, with a high specific surface area (1170 m2 g?1). These N‐doped nanoporous carbon/graphene nanosheets are used as the nonprecious metal electrocatalysts for oxygen reduction and exhibit a high onset potential (0.92 V vs reversible hydrogen electrode; RHE) and a large limiting current density (5.2 mA cm?2 at 0.60 V). To further increase the oxygen reduction performance, nanoporous Co‐Nx/carbon nanosheets are also prepared by using cobalt nitrate and zinc nitrate as cometal sources, which reveal higher onset potential (0.96 V) than both commercial Pt/C (0.94 V) and N‐doped nanoporous carbon/graphene nanosheets. Such nanoporous Co‐Nx/carbon nanosheets also exhibit good performance such as high activity, stability, and methanol tolerance in acidic media. 相似文献
8.
Recent Progress in MOF‐Derived,Heteroatom‐Doped Porous Carbons as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction in Fuel Cells
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Currently, developing nonprecious‐metal catalysts to replace Pt‐based electrocatalysts in fuel cells has become a hot topic because the oxygen reduction reaction (ORR) in fuel cells often requires platinum, a precious metal, as a catalyst, which is one of the major hurdles for commercialization of the fuel cells. Recently, the newly emerging metal‐organic frameworks (MOFs) have been widely used as self‐sacrificed precursors/templates to fabricate heteroatom‐doped porous carbons. Here, the recent progress of MOF‐derived, heteroatom‐doped porous carbon catalysts for ORR in fuel cells is systematically reviewed, and the synthesis strategies for using different MOF precursors to prepare heteroatom‐doped porous carbon catalysts, including the direct carbonization of MOFs, MOF and heteroatom source mixture carbonization, and MOF‐based composite carbonization are summarized. The emphasis is placed on the precursor design of MOF‐derived metal‐free catalysts and transition‐metal‐doped carbon catalysts because the MOF precursors often determine the microstructures of the derived porous carbon catalysts. The discussion provides a useful strategy for in situ synthesis of heteroatom‐doped carbon ORR electrocatalysts by rationally designing MOF precursors. Due to the versatility of MOF structures, MOF‐derived porous carbons not only provide chances to develop highly efficient ORR electrocatalysts, but also broaden the family of nanoporous carbons for applications in supercapacitors and batteries. 相似文献
9.
NiCo Alloy Nanoparticles Decorated on N‐Doped Carbon Nanofibers as Highly Active and Durable Oxygen Electrocatalyst
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Yue Fu Hai‐Yang Yu Cong Jiang Tian‐Heng Zhang Run Zhan Xiaowei Li Jian‐Feng Li Jing‐Hua Tian Ruizhi Yang 《Advanced functional materials》2018,28(9)
The exploring of catalysts with high‐efficiency and low‐cost for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is one of the key issues for many renewable energy systems including fuel cells, metal–air batteries, and water splitting. Despite several decades pursuing, bifunctional oxygen catalysts with high catalytic performance at low‐cost, especially the one that could be easily scaled up for mass production are still missing and highly desired. Herein, a hybrid catalyst with NiCo alloy nanoparticles decorated on N‐doped carbon nanofibers is synthesized by a facile electrospinning method and postcalcination treatment. The hybrid catalyst NiCo@N‐C 2 exhibits outstanding ORR and OER catalytic performances, which is even surprisingly superior to the commercial Pt/C and RuO2 catalysts, respectively. The synergetic effects between alloy nanoparticles and the N‐doped carbon fiber are considered as the main contributions for the excellent catalytic activities, which include decreasing the intrinsic and charge transfer resistances, increasing C?C, graphitic‐N/pyridinic‐N contents in the hybrid catalyst. This work opens up a new way to fabricate high‐efficient, low‐cost oxygen catalysts with high production. 相似文献
10.
Junxing Han Xiaoyi Meng Liang Lu Juanjuan Bian Zhipeng Li Chunwen Sun 《Advanced functional materials》2019,29(41)
Highly efficient non‐noble metal electrocatalysts are vital for metal–air batteries and fuel cells. Herein, a noble‐metal–free single‐atom Fe‐N x‐C electrocatalyst is synthesized by incorporating Fe‐Phen complexes into the nanocages in situ during the growth of ZIF‐8, followed by pyrolysis at 900 °C under inert atmosphere. Fe‐Phen species provide both Fe2+ and the organic ligand (Phen) simultaneously, which play significant roles in preparing single‐atom catalysts. The obtained Fe‐Nx‐C exhibits a half‐wave potential of 0.91 V for the oxygen reduction reaction, higher than that of commercial Pt/C (0.82 V). As a cathode catalyst for primary zinc–air batteries (ZABs), the battery shows excellent electrochemical performances in terms of the high open‐circuit voltage (OCV) of 1.51 V and a high power density of 96.4 mW cm?2. The rechargeable ZAB with Fe‐Nx‐C catalyst and the alkaline electrolyte shows a remarkable cycling performance for 300 h with an initial round‐trip efficiency of 59.6%. Furthermore, the rechargeable all‐solid‐state ZABs with the Fe‐Nx‐C catalyst show high OCV of 1.49 V, long cycle life for 120 h, and foldability. The single‐atom Fe‐Nx‐C electrocatalyst may function as a promising catalyst for various metal–air batteries and fuel cells. 相似文献
11.
Hsin‐Chih Huang Indrajit Shown Sun‐Tang Chang Hsin‐Cheng Hsu He‐Yun Du Ming‐Cheng Kuo Ken‐Tsung Wong Sea‐Fu Wang Chen‐Hao Wang Li‐Chyong Chen Kuei‐Hsien Chen 《Advanced functional materials》2012,22(16):3500-3508
Non‐precious metal catalysts of the oxygen reduction reaction are highly favored for use in polymer electrolyte fuel cells (PEFC) because of their relatively low cost. Here, a new carbon‐black‐supported pyrolyzed Co‐corrole (py‐Co‐corrole/C) catalyst of the oxygen reduction reaction (ORR) in a PEFC cathode is demonstrated to have high catalytic performance. The py‐Co‐corrole/C at 700 °C exhibits optimized ORR activity and participates in a direct four‐electron reduction pathway for the reduction of O2 to H2O. The H2‐O2 PEFC test of py‐Co‐corrole/C in the cathode reveals a maximum power density of 275 mW cm?2, which yields a higher performance and a lower Co loading than previous studies of Co‐based catalysts for PEFCs. The enhancement of the ORR activity of py‐Co‐corrole/C is attributable to the four‐coordinated Co‐corrole structure and the oxidation state of the central cobalt. 相似文献
12.
Wenzhe Tu Kai Chen Lujun Zhu Huachao Zai Bin E Xiaoxing Ke Changfeng Chen Manling Sui Qi Chen Yujing Li 《Advanced functional materials》2019,29(7)
Surface engineering has been found to be effective in promoting the catalytic activities of noble‐metal‐based nanocatalysts. In this contribution, by using the PtCuxNi ternary alloy nanocrystal (NC) as the model catalyst, a surface tungsten(W)‐doping strategy, combining a surface oxidative acid treatment protocol, can effectively boost the electrocatalytic activities of the NCs in oxygen reduction reaction. The W‐doped PtCuxNi alloy catalysts show obvious enhancement in electrochemical surface area and mass activity and slightly enhanced specific activity compared with the undoped catalyst. Based on the experimental evidence, it is proposed that the W doping involves a surface reconstruction by first removing the surface Pt atoms from the NC and then reducing them back to the surface. The existence of surface Ni atoms may be crucial in promoting the catalytic activities possibly through their electronic interactions to the active sites. The durability of the W‐doped PtCuxNi catalysts is also enhanced possibly due to the pinning effect of surface W atoms. Therefore, the surface engineering of PtCuxNi ternary alloy by W atoms can effectively modulate its activity and durability. 相似文献
13.
Hong Zhong Rongjian Sa Haowei Lv Shuailong Yang Daqiang Yuan Xinchen Wang Ruihu Wang 《Advanced functional materials》2020,30(35)
The visible‐light‐driven photocatalytic CO2 reduction is one appealing approach to simultaneously mitigate the energy crisis and environmental issues. It is highly desirable but challenging to selectively and efficiently convert CO2 into desirable products. Herein, a covalent organic framework hosting metalloporphyrin‐based carbon dots (M‐PCD@TD‐COF, M = Ni, Co, and Fe) is first presented, which serves as heterogeneous catalysts for CO2 photoreduction. M‐PCD@TD‐COF not only enriches available COF‐based catalytic materials, but also provides suitable environment for CO2 adsorption and activation on metalloporphyrin‐based carbon dots. The advantages of the host environment in COFs are highlighted by the satisfactory catalytic activity and remarkable selectivity of CO2‐to‐CO conversion over H2 generation up to 98%. The photocatalytic system is effective for both pure CO2 and the simulated flue gas. This work provides new protocols for the rational design of COF‐based heterogeneous catalysts for selective CO2 photoreduction. 相似文献
14.
Zhongxiang Wang Xiaozhang Yao Yongqiang Kang Linqing Miao Dongsheng Xia Lin Gan 《Advanced functional materials》2019,29(35)
Carbon‐supported low‐Pt ordered intermetallic nanoparticulate catalysts (PtM3, M = Fe, Co, and Ni) are explored in order to enhance the oxygen reduction reaction (ORR) activity while achieving a high stability compared to previously reported Pt‐richer ordered intermetallics (Pt3M and PtM) and low‐Pt disordered alloy catalysts. Upon high‐temperature thermal annealing, ordered PtCo3 intermetallic nanoparticles are successfully prepared with minimum particle sintering. In contrast, the PtFe3 catalyst, despite the formation of ordered structure, suffers from obvious particle sintering and detrimental metal–support interaction, while the PtNi3 catalyst shows no structural ordering transition at all but significant particle sintering. The ordered PtCo3 catalyst exhibits durably thin Pt shells with a uniform thickness below 0.6 nm (corresponding to 2–3 Pt atomic layers) and a high Co content inside the nanoparticles after 10 000 potential cycling, leading to a durably compressive Pt surface and thereby both high activity (fivefold vs a commercial Pt catalyst and 1.7‐fold vs an ordered PtCo intermetallic catalyst) and high durability (5 mV loss in half‐wave potential and 9% drop in mass activity). These results provide a new strategy toward highly active and durable ORR electrocatalysts by rational development of low‐Pt ordered intermetallics. 相似文献
15.
Wei‐Hong Lai Bin‐Wei Zhang Zhenpeng Hu Xi‐Ming Qu Yan‐Xia Jiang Yun‐Xiao Wang Jia‐Zhao Wang Hua Kun Liu Shu‐Lei Chou 《Advanced functional materials》2019,29(13)
Single‐atom Pt and bimetallic Pt3Co are considered the most promising oxygen reduction reaction (ORR) catalysts, with a much lower price than pure Pt. The combination of single‐atom Pt and bimetallic Pt3Co in a highly active nanomaterial, however, is challenging and vulnerable to agglomeration under realistic reaction conditions, leading to a rapid fall in the ORR. Here, a sustainable quasi‐Pt‐allotrope catalyst, composed of hollow Pt3Co (H‐PtCo) alloy cores and N‐doped carbon anchoring single atom Pt shells (Pt1N‐C), is constructed. This unique nanoarchitecture enables the inner and exterior spaces to be easily accessible, exposing an extra‐high active surface area and active sites for the penetration of both aqueous and organic electrolytes. Moreover, the novel Pt1N‐C shells not only effectively protect the H‐PtCo cores from agglomeration but also increase the efficiency of the ORR in virtue of the isolated Pt atoms. Thus, the H‐PtCo@Pt1N‐C catalyst exhibits stable ORR without any fade over a prolonged 10 000 cycle test at 0.9 V in HClO4 solution. Furthermore, this material can offer efficient and stable ORR activities in various organic electrolytes, indicating its great potential for next‐generation lithium–air batteries as well. 相似文献
16.
Qiuju Wang Liyu Chen Zheng Liu Nobuko Tsumori Mitsunori Kitta Qiang Xu 《Advanced functional materials》2019,29(39)
Dehydrogenation of formic acid (FA) is a promising alternative to fossil fuels, to provide clean energy for the future energy economy. The synthesis of highly active catalysts for FA dehydrogenation at room temperature has attracted a lot of attention. Herein, for the first time, highly active aurum–palladium nanoparticles (AuPd NPs) immobilized on nitrogen (N)‐doped porous carbon are fabricated through a phosphate‐mediation approach. The N‐doped carbon anchored with phosphate, which can be removed in alkaline solution during the reduction process of metal ions, shows an enhanced performance of absorbing and dispersion of both Au and Pd ions, which is a key to the synthesis of highly dispersed ultrafine AuPd NPs. The as‐prepared catalyst (designated as Au2Pd3@(P)N‐C) exhibits an extraordinarily high turnover frequency of 5400 h?1 and a 100% H2 selectivity for FA dehydrogenation at 30 °C. This phosphate‐mediation approach provides a new way to fabricate highly active metal NPs for catalytic application, pushing heterogeneous catalysts forward for practical usage in energy storage and conversion. 相似文献
17.
Francesco Basile Patricia Benito Simone Bugani Wout De Nolf Giuseppe Fornasari Koen Janssens Luciano Morselli Erika Scavetta Domenica Tonelli Angelo Vaccari 《Advanced functional materials》2010,20(23):4117-4126
Active‐phase‐coated metallic supports as structured catalysts are gaining attention in endothermic and exothermic processes because they improve heat transfer. The deposition of a well‐adhered and stable catalyst layer on the metallic support constitutes an important feature for the successful application of the final material. In this work, coating of FeCrAlY foams is performed by a one‐step electrosynthesis‐deposition of hydrotalcite‐type compounds, precursors of catalysts active in endothermic steam methane reforming. The catalysts are studied at different length scales by using, for the first time, a combination of several techniques: SEM/EDS and X‐ray fluorescence, X‐ray powder diffraction and absorption‐tomography experiments on the micro‐ and nanoscales at a synchrotron facility. The results show that the morphology of the coating depends on the synthesis conditions and that the catalyst may be described as Ni metal crystallites dispersed on γ‐Al2O3, homogeneously coating the FeCrAlY foam. 相似文献
18.
Chun Cheng Yang Shi Feng Zai Yi Tong Zhou Li Du Qing Jiang 《Advanced functional materials》2019,29(27)
Rational design of non‐noble metal catalysts with robust and durable electrocatalytic activity for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is extremely important for renewable energy conversion and storage, regenerative fuel cells, rechargeable metal–air batteries, water splitting etc. In this work, a unique hybrid material consisting of Fe3C and Co nanoparticles encapsulated in a nanoporous hierarchical structure of N‐doped carbon (Fe3C‐Co/NC) is fabricated for the first time via a facile template‐removal method. Such an ingenious structure shows great features: the marriage of 1D carbon nanotubes and 2D carbon nanosheets, abundant active sites resulting from various active species of Fe3C, Co, and NC, mesoporous carbon structure, and intimate integration among Fe3C, Co, and NC. As a multifunctional electrocatalyst, the Fe3C‐Co/NC hybrid exhibits excellent performance for ORR, OER, and HER, outperforming most of reported triple functional electrocatalysts. This study provides a new perspective to construct multifunctional catalysts with well‐designed structure and superior performance for clean energy conversion technologies. 相似文献
19.
Pyridinic‐Nitrogen‐Dominated Graphene Aerogels with Fe–N–C Coordination for Highly Efficient Oxygen Reduction Reaction
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Xiaoyang Cui Shubin Yang Xingxu Yan Jiugou Leng Shuang Shuang Pulickel M. Ajayan Zhengjun Zhang 《Advanced functional materials》2016,26(31):5708-5717
Here, pyridinic nitrogen dominated graphene aerogels with/without iron incorporation (Fe‐NG and NG) are prepared via a facile and effective process including freeze‐drying of chemically reduced graphene oxide with/without iron precursor and thermal treatment in NH3. A high doping level of nitrogen has been achieved (up to 12.2 at% for NG and 11.3 at% for Fe‐NG) with striking enrichment of pyridinic nitrogen (up to 90.4% of the total nitrogen content for NG, and 82.4% for Fe‐NG). It is found that the Fe‐NG catalysts display a more positive onset potential, higher current density, and better four‐electron selectivity for ORR than their counterpart without iron incorporation. The most active Fe‐NG exhibits outstanding ORR catalytic activity, high durability, and methanol tolerance ability that are comparable to or even superior to those of the commercial Pt/C catalyst at the same catalyst loading in alkaline environment. The excellent ORR performance can be ascribed to the synergistic effect of pyridinic N and Fe‐N x sites (where iron probably coordinates with pyridinic N) that serve as active centers for ORR. Our Fe‐NG can be developed into cost‐effective and durable catalysts as viable replacements of the expensive Pt‐based catalysts in practical fuel cell applications. 相似文献
20.
Scale‐Up Biomass Pathway to Cobalt Single‐Site Catalysts Anchored on N‐Doped Porous Carbon Nanobelt with Ultrahigh Surface Area
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Youqi Zhu Wenming Sun Wenxing Chen Tai Cao Yu Xiong Jun Luo Juncai Dong Lirong Zheng Jian Zhang Xiaolu Wang Chen Chen Qing Peng Dingsheng Wang Yadong Li 《Advanced functional materials》2018,28(37)
Porous Co? N? C catalysts with ultrahigh surface area are highly required for catalytic reactions. Here, a scale‐up method to synthesize gram‐quantities of isolated Co single‐site catalysts anchored on N‐doped porous carbon nanobelt (Co‐ISA/CNB) by pyrolysis of biomass‐derived chitosan is reported. The usage of ZnCl2 and CoCl2 salts as effective activation–graphitization agents can introduce a porous belt‐like nanostructure with ultrahigh specific surface area (2513 m2 g?1) and high graphitization degree. Spherical aberration correction electron microscopy and X‐ray absorption fine structure analysis reveal that Co species are present as isolated single sites and stabilized by nitrogen in CoN4 structure. All these characters make Co‐ISA/CNB an efficient catalyst for selective oxidation of aromatic alkanes at room temperature. For oxidation of ethylbenzene, the Co‐ISA/CNB catalysts yield a conversion up to 98% with 99% selectivity, while Co nanoparticles are inert. Density functional theory calculations reveal that the generated Co?O centers on isolated Co single sites are responsible for the excellent catalytic efficiency. 相似文献