FeNi Nanoparticles Coated on N-doped Ultrathin Graphene-like Nanosheets as Stable Bifunctional Catalyst for Zn-Air Batteries

High-performance and low-cost bifunctional catalysts are crucial to energy conversion and storage devices. Herein, a novel oxygen electrode catalyst with high oxygen evolution reaction and oxygen reduction reaction (OER/ORR) performance is reported based on bimetal FeNi nanoparticles anchored on N-doped graphene-like carbon (FeNi/N−C). The complete 2D ultrathin carbon nanosheet is induced by etching and stripping of molten sodium chloride and its ions in the carbonization process at suitable temperature. The obtained FeNi/N−C catalyst exhibits rapid reaction kinetics for OER, efficient four electron transfer for ORR, and outstanding bifunctional performance with reversible oxygen electrode index of 0.87 V for OER/ORR. Zn-air batteries with a high open-circuit voltage of 1.46 V and a stable discharge voltage of 1.23 V are assembled using liquid electrolytes, zinc sheet as Zn-electrode and FeNi/N−C coating on carbon cloth as air-electrode. The specific capacity is as high as 816 mAh g⁻¹ and there is extremely little decay after charge-discharge cycle time of 275 h for the FeNi/N−C as oxygen electrode catalyst in Zn-air battery, which are much better than that assembled with Pt/C−RuO₂ catalyst.     

溶剂热法制备磷掺杂碳纳米管作为氧气还原和氧气析出反应双功能电催化剂的研究

对氧气还原(ORR)和氧气析出(OER)反应都具有催化活性的双功能催化剂在金属-空气电池中起着关键作用.本文通过溶剂热反应,一步原位合成了磷掺杂碳纳米管(P-CNT).旋转环盘电极测试表明磷掺杂能够明显提高碳纳米管的催化活性,P-CNT在碱性电解质中对ORR和OER都具有优异的催化活性.P-CNT对ORR的催化还原为近4电子反应,可与商业催化剂Pt/C(20 wt%)相比;而其对OER的催化活性则高于Pt/C(20 wt%).此外,P-CNT的长期稳定性优于Pt/C(20 wt%).P-CNT对ORR和OER的高催化活性和稳定性主要归因于磷对碳的掺杂以及磷与碳间强的化学键合.     

Red Bean Pod Derived Heterostructure Carbon Decorated with Hollow Mixed Transition Metals as a Bifunctional Catalyst in Zn-Air Batteries

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.     

Paper-derived cobalt and nitrogen co-doped carbon nanotube@porous carbon as a nonprecious metal electrocatalyst for the oxygen reduction reaction

The oxygen reduction reaction (ORR) is a vitally important process in fuel cells. The development of high-performance and low-cost ORR electrocatalysts with outstanding stability is essential for the commercialization of the electrochemical energy technology. Herein, we report a facile synthesis of cobalt (Co) and nitrogen (N) co-doped carbon nanotube@porous carbon (Co/N/CNT@PC-800) electrocatalyst through a one-step pyrolysis of waste paper, dicyandiamide, and cobalt(II) acetylacetonate. The surface of the hierarchical porous carbon supported a large number of carbon nanotubes (CNTs), which were derived from dicyandiamide through the catalysis of Co. The addition of Co resulted in the formation of a hierarchical micro/mesoporous structure, which was beneficial for the exposure of active sites and rapid transportation of ORR-relevant species (O₂, H⁺, OH^?, and H₂O). The doped N and Co formed more active sites to enhance the ORR activity of the electrocatalyst. The Co/N/CNT@PC-800 material exhibited optimal ORR performance with an onset potential of 0.005 V vs. Ag/AgCl and a half-wave potential of –0.173 V vs. Ag/AgCl. Meanwhile, the electrocatalyst showed an excellent methanol tolerance and a long-term operational durability than that of Pt/C, as well as a quasi-four-electron reaction pathway. The low-cost and simple synthesis approach makes the Co/N/CNT@PC-800 a prospective electrocatalyst for the ORR. Furthermore, this work provides an alternative approach for exploring the use of biomass-derived electrocatalysts for renewable energy applications.     

三种碳材料上原位电沉积AuPt合金的催化性能

在碳纸（CP）及涂覆了碳粉科琴黑（KB）或石墨烯纳米片（GNs）的碳纸上,原位电沉积了AuPt合金,制备成CP/AuPt、CP/KB/AuPt、CP/GNs/AuPt三种空气电极。对比研究发现,以石墨烯纳米片为载体的CP/GNs/AuPt空气电极上,AuPt合金载量高,颗粒分散均匀,粒径约为100 nm左右,Au和Pt的含量分别为78.84%（n/n）和21.16%（n/n）。在0.1 mol·L^-1 KOH溶液中氧还原反应的起峰电势为0.93 V,催化活性和稳定性优于其他两种空气电极。分析认为,石墨烯纳米片具有高导电性、高比表面积以及较多的缺陷活性位点,有利于AuPt合金在其上均匀电沉积且沉积载量较高,同时GNs本身具有一定的催化活性,两者能够产生协同催化作用,提高了CP/GNs/AuPt电极的催化性能。     

Nitrogen‐Doped Graphitic Porous Carbon Nanosheets Derived from In Situ Formed g‐C3N4 Templates for the Oxygen Reduction Reaction

Heteroatom‐doped carbon materials have been considered as potential substitutes for Pt‐based electrocatalysts for the oxygen reduction reaction (ORR) in alkaline fuel cells. Here we report the synthesis of oxygen‐containing nitrogen‐doped carbon (ONC) nanosheets through the carbonization of a mixture that contained glucose and dicyandiamide (DCDA). In situ formed graphitic carbon nitride (g‐C₃N₄) derived from DCDA provided a nitrogen‐rich template, thereby facilitating the formation of ONC nanosheets. The resultant ONC materials with high nitrogen content, high specific surface areas, and highly mesoporous total volume displayed excellent electrochemical performance, including a similar ORR onset potential, half‐potential, a higher diffusion‐limited current, and excellent tolerance to methanol than that of the commercial Pt/C catalyst, respectively. Moreover, the ONC‐850 nanosheet displayed high long‐term durability even after 1000 cycles as well as a high electron transfer number of 3.92 (4.0 for Pt/C). Additionally, this work provides deeper insight into these materials and a versatile strategy for the synthesis of cost‐effective 2D N‐doped carbon electrocatalysts.     

Integrating NiCo Alloys with Their Oxides as Efficient Bifunctional Cathode Catalysts for Rechargeable Zinc–Air Batteries

The lack of high‐efficient, low‐cost, and durable bifunctional electrocatalysts that act simultaneously for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is currently one of the major obstacles to commercializing the electrical rechargeability of zinc–air batteries. A nanocomposite CoO‐NiO‐NiCo bifunctional electrocatalyst supported by nitrogen‐doped multiwall carbon nanotubes (NCNT/CoO‐NiO‐NiCo) exhibits excellent activity and stability for the ORR/OER in alkaline media. More importantly, real air cathodes made from the bifunctional NCNT/CoO‐NiO‐NiCo catalysts further demonstrated superior performance to state‐of‐the‐art Pt/C or Pt/C+IrO₂ catalysts in primary and rechargeable zinc–air batteries.     

Carbon black supported PtCu nanoparticles derived from mix-phased Cu precursor for high-performanced oxygen reduction reaction in acid medium

Alloying high-cost Pt with transition metals has been considered as an effective route to synthesize the electrocatalysts with low Pt loading and excellent activity towards oxygen reduction reaction (ORR) under acid solution. The galvanic replacement method, as featured with efficiency and simplicity, is widely reported to produce Pt-based bimetallic alloys and thereby declare the significance of reductive transition metal precursor on the enhancement of ORR performance. Herein, mix-phased Cu−Cu₂O precursor was applied to prepare carbon black supported highly dispersed PtCu alloy nanoparticles (PtCu/C). The proper Cu−Cu₂O ratios can exactly facilitate the generation of small sized PtCu alloy nanoparticles with regulated bimetallic content. Meanwhile, the Cu₂O phase is revealed to benefit the electron transfer from Pt to Cu and thus improve the intrinsic activity of Pt active sites. And the metallic Cu can favor the promotion of electrochemical active surface area. Consequently, the as-prepared PtCu/C behaves impressive ORR activity with half-wave potential of 0.88 V (vs. RHE) and mass activity of 0.49 A cm⁻² mg_Pt⁻¹ at 0.8 V, which is 9.8 times of commercial Pt/C catalysts. Our work will offer helpful advices for the development and regulation of novel Pt-based alloy materials towards diverse electrocatalysis.     

三种碳材料上原位电沉积AuPt合金的催化性能

在碳纸(CP)及涂覆了碳粉科琴黑(KB)或石墨烯纳米片(GNs)的碳纸上,原位电沉积了Au Pt合金,制备成CP/Au Pt、CP/KB/Au Pt、CP/GNs/Au Pt三种空气电极。对比研究发现,以石墨烯纳米片为载体的CP/GNs/Au Pt空气电极上,Au Pt合金载量高,颗粒分散均匀,粒径约为100 nm,Au和Pt的含量分别为78.84%(n/n)和21.16%(n/n)。在0.1 mol·L-1 KOH溶液中氧还原反应的起峰电势为0.93 V,催化活性和稳定性优于其他两种空气电极。分析认为,石墨烯纳米片具有高导电性、高比表面积以及较多的缺陷活性位点,有利于Au Pt合金在其上均匀电沉积且沉积载量较高,同时GNs本身具有一定的催化活性,两者能够产生协同催化作用,提高了CP/GNs/Au Pt电极的催化性能。     

Pyrolytic Carbon‐coated Cu‐Fe Alloy Nanoparticles with High Catalytic Performance for Oxygen Electroreduction

Well‐dispersed carbon‐coated or nitrogen‐doped carbon‐coated copper‐iron alloy nanoparticles (FeCu@C or FeCu@C?N) in carbon‐based supports are obtained using a bimetallic metal‐organic framework (Cu/Fe‐MOF‐74) or a mixture of Cu/Fe‐MOF‐74 and melamine as sacrificial templates and an active‐component precursor by using a pyrolysis method. The investigation results attest formation of Cu?Fe alloy nanoparticles. The obtained FeCu@C catalyst exhibits a catalytic activity with a half‐wave potential of 0.83 V for oxygen reduction reaction (ORR) in alkaline medium, comparable to that on commercial Pt/C catalyst (0.84 V). The catalytic activity of FeCu@C?N for ORR (E_half‐wave=0.87 V) outshines all reported analogues. The excellent performance of FeCu@C?N should be attributed to a change in the energy of the d‐band center of Cu resulting from the formation of the copper–iron alloy, the interaction between alloy nanoparticles and supports and N‐doping in the carbon matrix. Moreover, FeCu@C and FeCu@C?N show better electrochemical stability and methanol tolerance than commercial Pt/C and are expected to be widely used in practical applications.     

Two-Dimensional Mesoporous Carbon Materials Derived from Fullerene Microsheets for Energy Applications

Porous carbon materials rich in defects are promising candidates in energy storage and conversion applications. Herein, a facile template-free approach is reported for the synthesis of a two-dimensional (2 D) mesoporous carbon material derived from fullerene (C₆₀) microsheets (FMSs) through simple heat treatment. The sample obtained at 1000 °C (FMS1000) shows a large surface area of 1507.6 m² g⁻¹ owing to the presence of mesopores and rich defects, which promote electron and mass transfer in the electrocatalytic process of the oxygen reduction reaction (ORR), showing an excellent performance with an onset potential of 0.95 V, a half-wave potential of 0.85 V, and long-term durability of 2000 cycles, comparable to the performance of commercial Pt/C. Moreover, FMS1000 displays a remarkable supercapacitive property with a specific capacitance of 330.7 F g⁻¹ at 0.2 A g⁻¹ and good long-term stability with a capacitance retention of 97 % over 50 000 cycles. Thus, a practical strategy for the production of mesoporous carbon materials with different morphological structures and porous defects as high-performance energy materials is advanced.     

氧还原和析氧反应的双功能电催化剂--氮磷共掺碳负载四氧化三钴

金属-空气电池具备诸多优势,譬如绿色环保、能量转化率高、启动快速、能量密度高、使用寿命和干态存储时间长等.与燃料电池相比,金属-空气电池结构简单,放电电压平稳,成本低,但依然存在一些制约发展的问题,如阴极催化剂.阴极催化剂在金属-空气电池中发挥催化氧还原反应(oxygen reduction reaction, ORR)和析氧反应(oxygen evolution reac-tion, OER)的关键作用.铂及其合金常用作 ORR的单功能催化剂,而钌和铱等是目前 OER催化效率最高的,但 ORR活性很低,因此需要开发出一种廉价而又具备双功能催化作用的催化剂.单异原子掺杂的碳基催化剂的研究集中在 ORR催化性能上,而多异原子共掺碳最近有研究表明具有双催化氧的性质,如氮磷共掺碳.在这些氮磷共掺的碳架中,氮磷共掺物起着 OER催化作用,掺氮物为 ORR催化的活性位点,而掺磷物起着强化作用.异原子掺杂负载的钴基催化剂(如掺氮还原氧化石墨烯载 Co3O4)是近年来双功能催化剂研究的另一个热点.钴基催化剂有着催化 ORR和 OER的多价价态,然而其本身导电性能差,这一缺陷可通过杂化石墨化碳来弥补,石墨化碳有着优良的导电性能.据我们所知,目前仍没有关于氮磷共掺碳负载的 Co3O4双催化氧的研究.我们合成了氮磷共掺碳(NPC)负载的 Co3O4(Co3O4/NPC),并首次探索了其氧还原和析氧性能. Co3O4/NPC合成分两步进行.首先通过三聚氰胺与植酸之间的酯化或缩聚覆盖在导电炭黑颗粒表面,在保护气氛下焙烧得到 NPC,然后经溶剂热反应以及空气中氧化合成 Co3O4/NPC.催化剂的性能综合考虑了催化活性和稳定性两方面.采用线性扫描伏安法评估了 OER和 ORR的催化活性.对于 OER, Co3O4/NPC的起始电势是0.54 V (以饱和甘汞电极为参比电极),在0.80 V时电流密度达到21.95 mA/cm2,均优于 Co3O4/C和 NPC. Co3O4/NPC的高效 OER催化可归因于氮磷共掺物与 Co3O4之间的协同作用.对于 ORR, Co3O4/NPC的催化效率与商用 Pt/C相近,它们的扩散极限电流密度分别为–4.49和–4.76 mA/cm2(E =–0.80 V).在 ORR过程中, Co3O4起到主要的催化作用.采用计时电流(电流-时间)法评估了催化剂的稳定性.经6 h测定,对于 OER, Co3O4/NPC剩46%电流;而对于 ORR,剩95%电流.整体而言, Co3O4/NPC在 OER和 ORR中都表现出高的催化效率以及良好的稳定性.     

Iron Carbide Nanoparticles Encapsulated in Mesoporous Fe‐N‐Doped Carbon Nanofibers for Efficient Electrocatalysis

Exploring low‐cost and high‐performance nonprecious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) in fuel cells and metal–air batteries is crucial for the commercialization of these energy conversion and storage devices. Here we report a novel NPMC consisting of Fe₃C nanoparticles encapsulated in mesoporous Fe‐N‐doped carbon nanofibers, which is synthesized by a cost‐effective method using carbonaceous nanofibers, pyrrole, and FeCl₃ as precursors. The electrocatalyst exhibits outstanding ORR activity (onset potential of ?0.02 V and half‐wave potential of ?0.140 V) closely comparable to the state‐of‐the‐art Pt/C catalyst in alkaline media, and good ORR activity in acidic media, which is among the highest reported activities of NPMCs.     

Co@Co3O4 Encapsulated in Carbon Nanotube‐Grafted Nitrogen‐Doped Carbon Polyhedra as an Advanced Bifunctional Oxygen Electrode

Efficient reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are vitally important for various energy conversion devices, such as regenerative fuel cells and metal–air batteries. However, realization of such electrodes is impeded by insufficient activity and instability of electrocatalysts for both water splitting and oxygen reduction. We report highly active bifunctional electrocatalysts for oxygen electrodes comprising core–shell Co@Co₃O₄ nanoparticles embedded in CNT‐grafted N‐doped carbon‐polyhedra obtained by the pyrolysis of cobalt metal–organic framework (ZIF‐67) in a reductive H₂ atmosphere and subsequent controlled oxidative calcination. The catalysts afford 0.85 V reversible overvoltage in 0.1 m KOH, surpassing Pt/C, IrO₂, and RuO₂ and thus ranking them among one of the best non‐precious‐metal electrocatalysts for reversible oxygen electrodes.     

Fe-N共掺杂的碳纳米管串联空心球对氧还原反应的电催化

以ZIF-8为模板,通过表面包覆聚多巴胺、同时刻蚀ZIF-8中的Zn²⁺,形成空心球,在与三氯化铁络合后,经高温碳化和氨气热处理,得到了高比表面积的Fe-N共掺杂的碳纳米管串联的碳纳米空心球催化剂. 氨气不仅刻蚀碳基底提高比表面积,还可还原铁元素形成Fe₄N纳米粒子,提升了催化剂对氧还原反应的电催化活性,其氧还原半波电位达0.79 V,仅比商业Pt/C低60 mV,而且其稳定性和耐甲醇性更优于商业Pt/C,展示出良好的燃料电池应用潜力.     

In-situ deposition of Pd/Pd_4S heterostructure on hollow carbon spheres as efficient electrocatalysts for rechargeable Li-O_2 batteries

The sluggish kinetics of oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) have always restricted the development of lithium oxygen batteries(LOBs).Herein,hollow carbon spheres loaded with Pd/Pd_4S heterostructure(Pd/Pd_4S@HCS) were successfully prepared via the in-situ deposition to improve the electrocatalytic activities for both ORR and OER in LOBs.With the welldispersed Pd/Pd_4S nanoparticles,the hierarchical composite with large specific surface area offers favorable transport channels for ions,electron and oxygen.Especially,the Pd/Pd_4S nanoparticles could exhibit excellent electrochemical performance for ORR and OER due to their intrinsic catalytic property and interfacial effect from the heterostructure.Therefore,the LOBs with Pd/Pd_4S@HCS as cathode catalyst show improved specific capacities,good rate ability and stable cycling performance.     

Metal Phthalocyanine‐Porphyrin‐based Conjugated Microporous Polymer‐derived Bifunctional Electrocatalysts for Zn‐Air Batteries

Conjugated microporous polymers (CMPs) as emerging porous materials with diverse structures and tunable building‐units have attracted much attention in the electrochemical field. Herein, we designed phthalocyanine‐porphyrin‐based conjugated microporous polymers as precursors for fabrication of Co, Fe, N tri‐doped graphene composites towards oxygen reduction and evolution reaction (ORR/OER). As expected, the elements cobalt and iron are well dispersed in graphene carbon and interact with the nitrogen sites, thereby providing extra electrocatalytic active sites and enhancing its overall conductivity. Benefiting from its unique design and structure, the obtained catalyst affords a superior bifunctional catalytic activity with a positive onset potential of 0.957 V for ORR, and a low overpotential of 0.36 V for OER. More attractively, the CoFeNG is employed as an air cathode catalyst in Zn‐air batteries, showing a maximum current density of 215 mA cm^?2 and good cycle stability for 20000 s. The rational design of phthalocyanine‐porphyrin‐based derivatives provides a feasible route for the construction of high‐performance ORR/OER catalysts.     

氮掺杂的类石墨烯纳米片的制备及其在锌-空气电池中的应用

采用一种简单方法制备具有优异氧还原反应(ORR)活性的、无金属的氮掺杂碳材料.以双氰胺(DCD)为氮源,蔗糖、β-环糊精和壳聚糖为不同的碳源,通过简单的热解法制备出氮掺杂的类石墨烯纳米片催化剂CN-nanosh(suc)、CN-nanosh(cyc)和CN-nanosh(ch).这些催化剂在碱性溶液中表现出优异的ORR...     

Integrated Ultrafine Co0.85Se in Carbon Nanofibers: An Efficient and Robust Bifunctional Catalyst for Oxygen Electrocatalysis

Transition-metal selenides are emerging as alternative bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR); however, their activity and stability are still less than desirable. Herein, ultrafine Co_0.85Se nanoparticles encapsulated into carbon nanofibers (CNFs), Co_0.85Se@CNFs, is reported as an integrated bifunctional catalyst for OER and ORR. This catalyst exhibits a low OER potential of 1.58 V vs. reversible hydrogen electrode (RHE) (E_{J=10, OER}) to achieve a current density (J) of 10 mA cm⁻² and a high ORR potential of 0.84 V vs. RHE (E_{J=−1, ORR}) to reach −1 mA cm⁻². Thus, the potential between E_{J=10, OER} and E_{J=−1, ORR} is only 0.74 V, indicating considerable bifunctional activity. The excellent bifunctionality can be attributed to high electronic conduction, abundant electrochemically active sites, and the synergistic effect of Co_0.85Se and CNFs. Furthermore, this Co_0.85Se@CNFs catalyst displays good cycling stability for both OER and ORR. This study paves a new way for the rational design of hybrid catalysts composed of transition-metal selenides and carbon materials for efficiently catalyzing OER and ORR.     

A review of transition metal‐based bifunctional oxygen electrocatalysts

Electrochemical energy storage and conversion devices play a key role in the development of clean, sustainable, and efficient energy systems to meet the sustainable growth of our society. However, challenging issues including the sluggish kinetics of oxygen electrode reactions involving the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are present, limiting the implementation of devices such as metal‐air batteries, water electrolyzers, and regenerative fuel cells. In this review, various monometallic and bimetallic transition metal oxides (TMOs) and hydroxides are summarized in terms of their application for ORR/OER, in which the merits and demerits of various precious metal and carbon‐based metal oxide materials are discussed, with requirements for better electrocatalysts and catalyst support being introduced as well. Following this, different approaches to improve catalytic activity such as the introduction of doping and defects, the manipulation of crystal facets, and the engineering of supports, compositions, and morphologies are summarized in which TMOs with improved ORR/OER catalytic activities can be synthesized, further improving the speed, stability, and polarization of electrochemical energy storage and conversion devices. Finally, perspectives into the improvement of performance and the better understanding of ORR/OER mechanisms for bifunctional electrocatalysts using in situ spectroscopic techniques and density functional theory calculations are also discussed.