Layered Crystalline and Amorphous Platinum Disulfide (PtS2): Contrasting Electrochemistry

Group 6 transition metal dichalcogenides (TMDs), such as MoS₂ and WS₂ have been extensively studied for various applications while few studies have delved into other TMDs such as platinum dichalcogenides. In this work, layered crystalline and amorphous platinum disulfide (PtS₂) were synthesized, characterised and their fundamental electrochemical properties were investigated. Both materials exhibited inherent oxidation and reduction reactions which would limit their operating potential window for sensing applications. Amorphous phase materials are considered to be promising electrocatalysts due to the porous, and nanostructured morphology with high concentration of unsaturated active sites. The electrocatalytic performances towards oxygen reduction (ORR) and hydrogen evolution reactions (HER) of crystalline and amorphous PtS₂ were analysed. Amorphous PtS₂ was found to exhibit superior electrocatalytic performances towards ORR and HER as compared to crystalline PtS₂. For HER, amorphous and crystalline PtS₂ have overpotential values of 0.30 V and 0.70 V (vs. RHE) at current density of 10 mA cm⁻², respectively. The influence of electrochemical reduction pre-treatment on their catalytic behaviours was also investigated. Electrochemical reduction pre-treatment on both crystalline and amorphous PtS₂ removed the oxidized sulfate groups and increased the proportion of Pt⁰ oxidation state which exposed more catalytic sites. As such, these materials were activated and displayed improved ORR and HER performances. Electrochemically reduced amorphous PtS₂ outperformed the untreated counterparts and exhibited the best HER performance with overpotential of 0.17 V (vs. RHE) at current density of −10 mA cm⁻². These findings provide insights into the electrochemical properties of noble metal PtS₂ in both crystalline and amorphous states which can be activated by electrochemical reduction pre-treatment.     

碳纳米管负载金属卟啉电催化剂制备及其催化活性

采用微波合成法制备了多壁碳纳米管负载钴卟啉(CoTMPP/MWNT)电催化剂,利用透射电子显微镜对催化剂微观结构进行了表征,并通过旋转圆盘和旋转环盘技术对电催化剂的氧还原活性进行了评价.结果表明,与有机回流合成法制备的催化剂相比,微波法合成的CoTMPP/MWNT催化剂具有更好的氧还原性能,半波电位正向移动110mV;与多孔碳为载体的CoTMPP/BP2000催化剂相比,多壁碳纳米管为载体的CoTMPP/MWNT电催化剂的起始电位高10mV,还原电流损失低21%,表现出更好的氧还原活性和稳定性.在CoTMPP/MWNT电催化剂表面进行的氧还原过程中电子转移数为3·6,H2O2生成量为18%.MWNT独特的电子特性、强抗腐蚀能力及其与活性钴离子之间的相互作用有助于改善催化剂的氧化还原性能.     

High Catalytic Activity of Nitrogen and Sulfur Co‐Doped Nanoporous Graphene in the Hydrogen Evolution Reaction

Chemical doping has been demonstrated to be an effective way to realize new functions of graphene as metal‐free catalyst in energy‐related electrochemical reactions. Although efficient catalysis for the oxygen reduction reaction (ORR) has been achieved with doped graphene, its performance in the hydrogen evolution reaction (HER) is rather poor. In this study we report that nitrogen and sulfur co‐doping leads to high catalytic activity of nanoporous graphene in HER at low operating potential, comparable to the best Pt‐free HER catalyst, 2D MoS₂. The interplay between the chemical dopants and geometric lattice defects of the nanoporous graphene plays the fundamental role in the superior HER catalysis.     

Preparation and Catalytic Activity of Carbon Nanotube-Supported Metalloporphyrin Electrocatalyst

The multiwalled carbon nanotube-supported CoTMPP (CoTMPP/MWNT) electrocatalyst was prepared by the microwave synthesis method, and its microstructure was characterized using transmission electron microscopy. The electrocatalytic performance of CoTMPP/MWNT for oxygen reduction reaction (ORR) was evaluated by rotating disc electrode and rotating ring disc electrode technique. Compared with the CoTMPP/MWNT electrocatalyst prepared by the traditional organic reflux method, the one prepared by the microwave synthesis method showed better performance for ORR, and the half-wave potential exhibited a positive shift of 110 mV. Compared with CoTMPP/BP2000, the CoTMPP/MWNT electrocatalyst showed a 10 mV higher on-set potential and a 21% lower reduction current loss in ORR, indicating that the CoTMPP/MWNT electrocatalyst had higher catalytic activity and better stability than CoTMPP/BP2000. The number of exchanged electrons during ORR and the yield of peroxide were 3.6 and 18%, respectively. The high corrosion resistance and unique electronic property of MWNT, and the interaction between MWNT and active metal ions can efficiently improve the electrocatalytic performance of the CoTMPP/MWNT catalyst.     

酸性和碱性溶液中金属氮碳材料氧还原和氢析出反应的理论研究

单原子催化剂(SAC)由于其低成本和在各种电催化反应中潜在的高催化活性而被认为是铂族金属的有前景的替代材料,但仍然缺乏对不同金属氮碳材料催化剂之间活性差异的原子机理的理解.在此,通过实验和理论研究相结合,研究了非贵金属氮碳材料(Me-N-C,Me = Fe和Co)作为模型催化剂,以探索在普遍的pH值下氧还原反应(ORR...     

Electrocatalytic Oxidation of Hydrogen Peroxide on Poly(m‐toluidine)‐Nickel Modified Carbon Paste Electrode in Alkaline Medium

The poly(m‐toluidine) film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of carbon paste electrode. Then transition metal ions of Ni(II) were incorporated to the polymer by immersion of the modified electrode in a 0.2 M NiSO₄, also the electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple. The electrocatalytic ability of Ni(II)/poly(m‐toluidine)/modified carbon paste electrode (Ni/PMT/MCPE) was demonstrated by electrocatalytic oxidation of hydrogen peroxide with cyclic voltammetry and chronoamperometry methods in the alkaline solution. The effects of scan rate and hydrogen peroxide concentration on the anodic peak height of hydrogen peroxide oxidation were also investigated. The catalytic oxidation peak current showed two linear ranges with different slopes dependent on the hydrogen peroxide concentration and the lower detection limit was 6.5 μM (S/N=3). The catalytic reaction rate constant, (k_h), was calculated 5.5×10² M^?1 s^?1 by the data of chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility and high catalytic activity toward the hydrogen peroxide oxidation. This method was also applied as a simple method for routine control and can be employed directly without any pretreatment or separation for analysis cosmetics products.     

Electrocatalytic Dioxygen Reduction at Glassy Carbon Electrode Modified with Polyaniline Grafted Multiwall Carbon Nanotube Film

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.     

Preparation of CoSe nanoparticles by microwave-assisted polyol method: effect of Se/Co ratio, support type and synthesis conditions on oxygen reduction activity

Highly methanol-tolerant CoSe nanoparticles supported on different carbon substrates were synthesized by microwave heating of glycerol solutions of cobalt(II) acetate and sodium selenite at different Se/Co mole ratios in the presence of different concentrations of acetic acid and ammonia. The resulting CoSe catalysts were used for the electrochemical oxygen reduction reaction (ORR) in acidic solution in the presence of methanol. The ORR activity of the catalyst was increased by increasing its Se content up to 50?mol%. The presence of acetic acid or ammonia in the synthesis solution significantly affects the electrocatalytic performance of the CoSe catalyst; highest activity was observed when the catalyst was synthesized at NH₃/Co(II) mole ratio of 6. Among the catalysts prepared on different supports including carbon black (Vulcan XC-72R), and nanoporous carbons synthesized from resorcinol-formaldehyde and phloroglucinol-formaldehyde resins, the one supported on the carbon prepared from the last resin exhibited highest electrocatalytic activity for ORR.     

Enhancing Hydrogen Evolution Activity of Au(111) in Alkaline Media through Molecular Engineering of a 2D Polymer

The electrochemical splitting of water holds promise for the storage of energy produced intermittently by renewable energy sources. The evolution of hydrogen currently relies on the use of platinum as a catalyst—which is scarce and expensive—and ongoing research is focused towards finding cheaper alternatives. In this context, 2D polymers grown as single layers on surfaces have emerged as porous materials with tunable chemical and electronic structures that can be used for improving the catalytic activity of metal surfaces. Here, we use designed organic molecules to fabricate covalent 2D architectures by an Ullmann‐type coupling reaction on Au(111). The polymer‐patterned gold electrode exhibits a hydrogen evolution reaction activity up to three times higher than that of bare gold. Through rational design of the polymer on the molecular level we engineered hydrogen evolution activity by an approach that can be easily extended to other electrocatalytic reactions.     

Synthesis and catalytic activity of platinum/porous silicon nanocomposites

Physicochemical characteristics of the functional electrode nanocomposites based on porous silicon with platinum nanoparticles were investigated with the use of electron microscopy, X-ray diffraction, and cyclic voltammetry. It is established that a decrease in the platinum nanoparticle size leads to an increase in catalytic activity of nanocomposites in the reactions of electrocatalytic oxygen reduction and hydrogen oxidation.     

A Nanoporous PdCo Alloy as a Highly Active Electrocatalyst for the Oxygen‐Reduction Reaction and Formic Acid Electrooxidation

A nanoporous (NP) PdCo alloy with uniform structure size and controllable bimetallic ratio was fabricated simply by one‐step mild dealloying of a PdCoAl precursor alloy. The as‐made alloy consists of a nanoscaled bicontinuous network skeleton with interconnected hollow channels that extend in all three dimensions. With a narrow ligament size distribution around 5 nm, the NP PdCo alloy exhibits much higher electrocatalytic activity towards the oxygen‐reduction reaction (ORR) with enhanced specific and mass activities relative to NP Pd and commercial Pt/C catalysts. A long‐term stability test demonstrated that NP PdCo has comparable catalytic durability with less loss of ORR activity and electrochemical surface area than Pt/C. The NP PdCo alloy also shows dramatically enhanced catalytic activity towards formic acid electrooxidation relative to NP Pd and Pd/C catalysts. The as‐made NP PdCo holds great application potential as a promising cathode as well as an anode electrocatalyst in fuel cells with the advantages of superior catalytic performance and easy preparation.     

Electrocatalytic oxidation of hydrogen peroxide and cysteine at a glassy carbon electrode modified with platinum nanoparticle-deposited carbon nanotubes.

A glassy carbon electrode modified with platinum nanoparticle-decorated carbon nanotubes (Pt-CNT/GCE) was prepared. The electrochemical behaviors for the catalysis oxidations of hydrogen peroxide and cysteine were studied. The Pt-CNT/GCE showed catalytic activity for electro-oxidation of hydrogen peroxide at 0.6 V in PBS (pH = 7.0) and for that of cysteine at 0.55 V in sulfuric acid medium (pH 相似文献   

铂基金属间化合物纳米晶的最新进展:可控合成与电催化应用

铂基金属间化合物纳米晶因其高度有序的结构特点,优异的抗氧化及耐腐蚀性能,作为电极材料被广泛应用于各类电催化反应,目前已有的PtCo金属间化合物纳米晶在燃料电池阴极反应(氧还原反应)中的活性和稳定性均达到了美国能源部(DOE) 2020年的目标。为了进一步提高金属间化合物纳米晶的电催化性能,需要对影响纳米晶电催化性能的因素进行深入研究。本文综述了铂基金属间化合物纳米晶的研究现状,着重介绍了铂基金属间化合物的可控合成策略及其在电催化领域的最新研究进展,分析总结了该领域存在的问题,并展望了其未来发展方向。     

Fabrication and Application of a Sensitive and Highly Stable Copper Hexacyanoferrate Modified Carbon Ionic Liquid Paste Electrode for Hydrogen Peroxide and Glucose Detection

A three‐factor mixture design and response surface methodology were employed to find the optimal weight ratio of graphite powder, n‐dodecylpyridinium hexafluorophosphate and paraffin for the fabrication of a copper hexacyanoferrate modified carbon ionic liquid paste electrode (CuHCFe‐CILPE). The fabricated sensor showed electrocatalytic activity towards oxidation and reduction of hydrogen peroxide. It also was observed that the electrocatalytic activity for hydrogen peroxide oxidation was much higher than the electrocatalytic activity for hydrogen peroxide reduction. Glucose oxidase was then successfully immobilized on the surface of the proposed sensor to examine the possibility of using CuHCFe‐CILPE for the biosensor fabrication.     

Thermodynamic guidelines for the design of bimetallic catalysts for oxygen electroreduction and rapid screening by scanning electrochemical microscopy. M-co (M: Pd, Ag, Au)

We propose guidelines for the design of improved bimetallic (and related) electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. This guide is based on simple thermodynamic principles assuming a simple mechanism where one metal breaks the oxygen-oxygen bond of molecular O(2) and the other metal acts to reduce the resulting adsorbed atomic oxygen. Analysis of the Gibbs free energies of these two reactions guides the selection of combinations of metals that can produce alloy surfaces with enhanced activity for the ORR when compared to the constituent metals. Selected systems have been tested by fabricating arrays of metallic catalysts consisting of various binary and ternary combinations of Pd, Au, Ag, and Co deposited on glassy carbon (GC) substrates. The electrocatalytic activity of these materials for the ORR in acidic medium was examined using scanning electrochemical microscopy (SECM) in a new rapid-imaging mode. This was used to rapidly screen arrays covering a wide range of catalyst compositions for their activity for the ORR in 0.5 M H(2)SO(4). Using the SECM technique, we have identified combinations of metals with enhanced electrocatalytic activities when compared with the constituent, pure metals. Addition of Co to Pd, Au, and Ag clearly decreases the ORR overpotential, in agreement with the proposed model. Catalyst spots that exhibited enhanced electrocatalytic activity in the SECM screening technique were then examined using classical rotating disk electrode (RDE) experiments. The activity of carbon black supported catalyst mixtures on a GC RDE and the electrocatalytic activity determined using the SECM screening technique showed excellent agreement. C/Pd-Co electrodes (10-30% Co) exhibited remarkable activity for ORR catalysis, close to that of carbon-supported Pt.     

精确可控串联策略触发高效的氧还原活性

探索高效、经济的非金属氧还原(ORR)电催化剂已成为电化学能源体系的关键.科学界最具挑战性的目标之一是通过合理地验证和精确地调节活性位点来设计结构明确、性能优异的催化剂材料.本文提出一种精确和可控的串联协同作用的活性位点策略,以提高MFCOFs的ORR催化活性.以亚胺-N、噻吩-S和三嗪-N等作为结构单元,通过精确的串...     

Pig Bone Derived Hierarchical Porous Carbon‐Supported Platinum Nanoparticles with Superior Electrocatalytic Activity Towards Oxygen Reduction Reaction

Hierarchical porous carbon (HPC) with nitrogen doped three dimension open macropore structure was prepared from pig bone, and applied for the support material for platinum nanoparticle (Pt NP) electrocatalyst. Compared with carbon black supported Pt NP electrocatalysts, the Pt/HPC exhibited larger electrochemical active surface area and enhanced catalytic properties for the oxygen reduction reaction (ORR) in terms of on‐set potential, current density, mass activity and stability. The superior catalytic activity is mainly attributed to the high surface area, hierarchical porous structures and the nitrogen‐doped surface properties of the HPC, indicating it is a promising support material for the ORR electrocatalysts.     

Nitrogen and Phosphorus Dual‐Doped Hierarchical Porous Carbon Foams as Efficient Metal‐Free Electrocatalysts for Oxygen Reduction Reactions

Despite tremendous progress in developing doped carbocatalysts for the oxygen reduction reaction (ORR), the ORR activity of current metal‐free carbocatalysts is still inferior to that of conventional Pt/C catalysts, especially in acidic media and neutral solution. Moreover, it also remains a challenge to develop an effective and scalable method for the synthesis of metal‐free carbocatalysts. Herein, we have developed nitrogen and phosphorus dual‐doped hierarchical porous carbon foams (HP‐NPCs) as efficient metal‐free electrocatalysts for ORR. The HP‐NPCs were prepared for the first time by copyrolyzing nitrogen‐ and phosphorus‐containing precursors and poly(vinyl alcohol)/polystyrene (PVA/PS) hydrogel composites as in situ templates. Remarkably, the resulting HP‐NPCs possess controllable nitrogen and phosphorus content, high surface area, and a hierarchical interconnected macro‐/mesoporous structure. In studying the effects of the HP‐NPCs on the ORR, we found that the as‐prepared HP‐NPC materials exhibited not only excellent catalytic activity for ORR in basic, neutral, and acidic media, but also much better tolerance for methanol oxidation and much higher stability than the commercial, state‐of‐the‐art Pt/C catalysts. Because of all these outstanding features, it is expected that the HP‐NPC material will be a very suitable catalyst for next‐generation fuel cells and lithium–air batteries. In addition, the novel synthetic method described here might be extended to the preparation of many other kinds of hierarchical porous carbon materials or porous carbon that contains metal oxide for wide applications including energy storage, catalysis, and electrocatalysis.     

Nanosheets with High-Performance Electrochemical Oxygen Reduction Reaction Revived from Green Walnut Peel

The synthesis of metal-free carbon-based electrocatalysts for oxygen reduction reactions (ORR) to replace conventional Pt-based catalysts has become a hot spot in current research. This work proposes an activation-assisted carbonization strategy, to manufacture N-doped ultra-thin carbon nanosheets (GWS180M800) with high catalytic activity, namely, melamine is used as an accelerator/nitrogen source, and walnut green peels biological waste as a carbon source. The melamine acts as a nitrogen donor in the hydrothermal process, effectively enhancing the nitrogen doping rate. The content of pyridine nitrogen groups accounts for up to 48.5% of the total nitrogen content. Electrochemical tests show that the GWS180M800 has excellent ORR electrocatalytic activity and stability, and makes a quasi-four-electron ORR pathway clear in the alkaline electrolyte. The initial potential and half slope potential are as high as 1.01 and 0.82 V vs. RHE, respectively. The GWS180M800 catalyst has a better ability to avoid methanol cross poisoning than Pt/C has. Compared with 20 wt% Pt/C, GWS180M800 has improved methanol tolerance and stability. It is a metal-free biochar ORR catalyst with great development potential and application prospects. This result provides a new space for the preparation of valuable porous nano-carbon materials based on carbonaceous solid waste and provides new ideas for catalyzing a wide range of electrochemical reactions in the future.     

Synthesis of Nanoporous Carbon–Cobalt‐Oxide Hybrid Electrocatalysts by Thermal Conversion of Metal–Organic Frameworks

Nanoporous carbon–cobalt‐oxide hybrid materials are prepared by a simple, two‐step, thermal conversion of a cobalt‐based metal–organic framework (zeolitic imidazolate framework‐9, ZIF‐9). ZIF‐9 is carbonized in an inert atmosphere to form nanoporous carbon–metallic‐cobalt materials, followed by the subsequent thermal oxidation in air, yielding nanoporous carbon–cobalt‐oxide hybrids. The resulting hybrid materials are evaluated as electrocatalysts for the oxygen‐reduction reaction (ORR) and the oxygen‐evolution reaction (OER) in a KOH electrolyte solution. The hybrid materials exhibit similar catalytic activity in the ORR to the benchmark, commercial, Pt/carbon black catalyst, and show better catalytic activity for the OER than the Pt‐based catalyst.