Pt-like Activity Research Articles

Cathodically activated Au/TiO2 nanocomposite synthesized by a new facile solvothermal method: An efficient electrocatalyst with Pt-like activity for hydrogen generation

We report here a facile, template-free and one-step solvothermal approach for the synthesis of high-temperature stable gold/titania nanocomposite (NCs), providing a new, simple, quick and inexpensive wet-chemical route. Our approach is based on the assembly of gold salt and titanium butoxide in dimethyl sulfoxide (DMSO). Also, we present here, for the first time, a cathodically activated Au/TiO2 catalyst with Pt/C activity for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 in the dark. The as-prepared (unactivated) Au/TiO2 NCs exhibits considerable electrocatalytic activity for H2 generation in the dark, with a low onset potential (EHER) of −64 mV vs. RHE, a Tafel slope (-bc) of 60 mV dec−1 and an exchange current density (jo) of 0.12 mA cm−2. Long-term stability and durability tests in 0.5 M H2SO4, employing cyclic voltammetry technique (10,000 of repetitive cycling) and 72 h of chronoamperometry measurements at a high cathodic potential (cathodic activation), reveal that the electrocatalyst activates during such aging processes yielding an activated Au/TiO2 catalyst with Pt/C-like activity for H2 generation (EHER -3 mV, -bc: 35 mV dec−1, and jo: 0.95 mA cm−2). The outstanding HER activity of the activated catalyst is discussed.

Robust photocatalytic hydrogen evolution over amorphous ruthenium phosphide quantum dots modified g-C3N4 nanosheet

The development of materials which meet the needs of both cost-efficiency and high performance for hydrogen evolution reaction is of great importance. However, developing photocatalysts with Pt-like activity still remains as a major challenge. Herein, we utilize ultrafine amorphous ruthenium phosphide (RP) nanoparticles as a high-efficient and robust cocatalyst to enhance the H2 production activity of g-C3N4 (g-CN). The RP/g-CN samples were prepared based on a facile in-situ growth phosphatization method. The optimum H2 evolution rate reached up to 2110 μmol h−1g−1 for 0.1%-RP/g-CN, which was 113.4 times as high as that of pristine g-C3N4 and 2.22 times of Pt-loaded g-C3N4. Furthermore, ruthenium is the cheapest platinum-group metal and its amount in the best RP/g-CN sample is only 0.1%, showing the superiority of competitive price and high activity. The introduction of ultrafine amorphous ruthenium phosphide accelerated the transfer rate of electrons and restrain the recombination of charge carriers. The amorphous ruthenium phosphide ultrafine nanoparticles could also serve as cocatalysts for hydrogen evolution. This work provides a promising alternative to expensive Pt-loaded photocatalyst for excellent hydrogen evolution performance under visible light irradiation.

Superhydrophilic amorphous Co–B–P nanosheet electrocatalysts with Pt-like activity and durability for the hydrogen evolution reaction

Superhydrophilic ternary Co–B–P nanosheets are developed as a hydrogen evolution electrocatalyst showing Pt-like catalytic activity and superior stability in alkaline media.

When NiO@Ni Meets WS2 Nanosheet Array: A Highly Efficient and Ultrastable Electrocatalyst for Overall Water Splitting.

The development of low-cost, high-efficiency, and stable bifunctional electrocatalysts toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance for large-scale water splitting. Here, we develop a new strategy for the first design and synthesis of a NiO@Ni decorated WS2 nanosheet array on carbon cloth (NiO@Ni/WS2/CC) composite. This composite serves as a unique three-dimensional (3D) synergistic electrocatalyst that not only combines the intrinsic properties of individual NiO@Ni and WS2, but also exhibits significantly improved HER and OER activities when compared to that of pure NiO@Ni and WS2. This electrocatalyst possesses Pt-like activity for HER and exhibits better OER performance than that for commercial RuO2, as well as demonstrating superior long-term durability in alkaline media. Furthermore, it enables an alkaline electrolyzer with a current density of 10 mA cm–2 at a cell voltage as 1.42 V, which is the lowest one among all reported values to date. The excellent performance is mainly attributed to the unique 3D configuration and multicomponent synergies among NiO, Ni, and WS2. Our findings provide a new idea to design advanced bifunctional catalysts for water splitting.

RuP2 -Based Catalysts with Platinum-like Activity and Higher Durability for the Hydrogen Evolution Reaction at All pH Values.

Highly active, stable, and cheap Pt-free catalysts for the hydrogen evolution reaction (HER) are under increasing demand for future energy conversion systems. However, developing HER electrocatalysts with Pt-like activity that can function at all pH values still remains as a great challenge. Herein, based on our theoretical predictions, we design and synthesize a novel N,P dual-doped carbon-encapsulated ruthenium diphosphide (RuP2 @NPC) nanoparticle electrocatalyst for HER. Electrochemical tests reveal that, compared with the Pt/C catalyst, RuP2 @NPC not only has Pt-like HER activity with small overpotentials at 10 mA cm-2 (38 mV in 0.5 m H2 SO4 , 57 mV in 1.0 m PBS and 52 mV in 1.0 m KOH), but demonstrates superior stability at all pH values, as well as 100 % Faradaic yields. Therefore, this work adds to the growing family of transition-metal phosphides/heteroatom-doped carbon heterostructures with advanced performance in HER.

PdCu@Pd Nanocube with Pt-like Activity for Hydrogen Evolution Reaction.

The electronic properties of metal surfaces can be modulated to weaken the binding energy of adsorbed H-intermediates on the catalyst surface, thus enhancing catalytic activity for the hydrogen evolution reaction (HER). Here we first prepare PdCu alloy nanocubes (NCs) by coreduction of Cu(acac)2 (acac = acetylacetonate) and Na2PdCl4 in the presence of oleylamine (OAm) and trioctylphosphine (TOP). The PdCu NC coated glassy carbon electrode is then anodized at a constant potential of 0.51 V vs Ag/AgCl at room temperature in 0.5 M H2SO4 solution for 10 s, which converts PdCu NCs into core@shell PdCu@Pd NCs that show much enhanced Pt-like activity for the HER and much more robust durability. The improvements in surface property and HER activity are rationalized based on strain and ligand effects that enhance the activity of the edge-exposed Pd atoms on core@shell PdCu@Pd structure. This work opens up a new perspective for simultaneously reducing metal Pd cost and achieving excellent performance toward the HER.

Ternary FexCo1-xP Nanowire Array as a Robust Hydrogen Evolution Reaction Electrocatalyst with Pt-like Activity: Experimental and Theoretical Insight.

Replacement of precious Pt with earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) holds great promise for clean energy devices, but the development of low-cost and durable HER catalysts with Pt-like activity is still a huge challenge. In this communication, we report on the development of self-standing ternary FexCo1-xP nanowire array on carbon cloth (FexCo1-xP/CC) as a Pt-free HER catalyst with activities being strongly related to Fe substitution ratio. Electrochemical tests show that Fe0.5Co0.5P/CC not only possesses Pt-like activity with the need of overpotential of only 37 mV to drive 10 mA cm-2, outperforming all non-noble-metal HER catalysts reported to date, but demonstrates superior long-term durability in 0.5 M H2SO4. Density functional theory calculations further reveal that Fe substitution of Co in CoP leads to more optimal free energy of hydrogen adsorption to the catalyst surface. This study offers us a promising flexible monolithic catalyst for practical applications.

High Pt-like activity of the Ni–Mo/graphene catalyst for hydrogen evolution from hydrolysis of ammonia borane

Ni nanocatalysts modified with a Mo dopant and a graphene support have been used as a low cost catalyst with Pt-like activity and robust durability for hydrogen evolution from the hydrolysis of ammonia borane under ambient atmosphere at room temperature.

A novel CoP/MoS2-CNTs hybrid catalyst with Pt-like activity for hydrogen evolution

A novel hybrid catalyst with Pt-like activity for the hydrogen evolution reaction is constructed by the in situ growth of CoP on the surface of MoS2 and CNTs.

A novel strategy for tailoring copper oxide cluster with Pt-like activity for photocatalytic hydrogen evolution

The production of hydrogen by solar-driven water splitting has attracted a lot attention as an ideal solution for global energy and environment issues. Platinum has been widely used as the cocatalyst for facilitating hydrogen evolution reaction, but the high cost and low abundance may limit the large-scale commercial application of solar-to-fuels technique. Here we report an active and cheap photocatalyst, using copper oxide as cocatalyst immobilized on anatase titanium dioxide. The hydrogen evolution efficiency from the copper oxide cocatalyst can be comparable to those of systems containing the well-known platinum cocatalysts. Therefore, this copper-based cocatalyst provides an inexpensive means of harnessing solar energy to achieve efficient hydrogen evolution from water splitting. The findings in this work may open the door for developing other noble-metal-free catalysts for photocatalysis and photoelectrochemistry.

Core/Shell Face-Centered Tetragonal FePd/Pd Nanoparticles as an Efficient Non-Pt Catalyst for the Oxygen Reduction Reaction.

We report the synthesis of core/shell face-centered tetragonal (fct)-FePd/Pd nanoparticles (NPs) via reductive annealing of core/shell Pd/Fe3O4 NPs followed by temperature-controlled Fe etching in acetic acid. Among three different kinds of core/shell FePd/Pd NPs studied (FePd core at ∼8 nm and Pd shell at 0.27, 0.65, or 0.81 nm), the fct-FePd/Pd-0.65 NPs are the most efficient catalyst for the oxygen reduction reaction (ORR) in 0.1 M HClO4 with Pt-like activity and durability. This enhanced ORR catalysis arises from the desired Pd lattice compression in the 0.65 nm Pd shell induced by the fct-FePd core. Our study offers a general approach to enhance Pd catalysis in acid for ORR.

A New Core/Shell NiAu/Au Nanoparticle Catalyst with Pt-like Activity for Hydrogen Evolution Reaction.

We report a general approach to NiAu alloy nanoparticles (NPs) by co-reduction of Ni(acac)2 (acac = acetylacetonate) and HAuCl4·3H2O at 220 °C in the presence of oleylamine and oleic acid. Subject to potential cycling between 0.6 and 1.0 V (vs reversible hydrogen electrode) in 0.5 M H2SO4, the NiAu NPs are transformed into core/shell NiAu/Au NPs that show much enhanced catalysis for hydrogen evolution reaction (HER) with Pt-like activity and much robust durability. The first-principles calculations suggest that the high activity arises from the formation of Au sites with low coordination numbers around the shell. Our synthesis is not limited to NiAu but can be extended to FeAu and CoAu as well, providing a general approach to MAu/Au NPs as a class of new catalyst superior to Pt for water splitting and hydrogen generation.

Ordered Mesoporous Porphyrinic Carbons for Oxygen Reduction Reaction: Pt-like Activity in Acidic Media and Active Site

The high cost of polymer electrolyte fuel cell (PEFC) systems, predominantly dictated by the platinum-based cathode catalysts for the oxygen reduction reaction (ORR), has critically impeded the widespread application of PEFCs. Therefore, the quest for low-cost yet high-performance non-precious metal catalysts has been of prime importance in recent years. We present a new class of self-supported, transition metal-doped ordered mesoporous porphyrinic carbon (M-OMPC; M=transition metal) catalysts, which were prepared by nanocasting mesoporous silica templates with metalloporphyrin precursors [1]. The preparation of M-OMPC catalysts is simple, tunable, scalable, and highly reproducible. Among the M-OMPC catalysts, FeCo-OMPC exhibits a very high ORR activity in an acidic medium, which is one of the best performances among the non-precious M/N/C catalysts, and outperformed the carbon-supported commercial Pt/C catalyst. Furthermore, the FeCo-OMPC showed superior long-term durability in ORR, compared to Pt/C; after cycling 10,000 times under O2 bubbling, the FeCo-OMPC exhibited 6-fold higher ORR activity than the Pt/C. The weakening of the interaction between oxygen atom and the FeCo-OMPC compared to Pt/C as well as high surface area of the former could be responsible for its significantly high ORR activity. We also systematically investigated the potential active sites for the ORR in the FeCo-OMPC catalysts, and could correlate the local coordination structure around metal centers and corresponding ORR activities [2]. The M-OMPC catalysts could suggest a new concept for future design of non-precious metal-based high-performing ORR catalysts. [1] J. Y. Cheon, T. Kim, Y. Choi, H. Y. Jeong, M. G. Kim, Y. J. Sa, J. Kim, Z. Lee, T.-H. Yang, K. Kwon, O. Terasaki, G.-G. Park, R. R. Adzic, S. H. Joo, Scientific Reports 3, 2715 (2013). [2] J. Y. Cheon, M. G. Kim, G.-G. Park, S. H. Joo, manuscript in preparation.

Fabrication of phosphonate functionalized platinum nanoclusters and their application in hydrogen peroxide sensing in the presence of oxygen

The water-soluble phosphonate functionalized spherical platinum nanoclusters (Pt-NCs) composed of primary nanoparticles are synthesized by the thermal decomposition of platinum(IV)-complex. The size, morphology and structure of Pt-NCs are analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Attachment of phosphonate groups on Pt surface is confirmed by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and zeta potential analysis. The phosphonate functionalized Pt-NCs efficiently suppress the oxygen reduction reaction (ORR) while fully preserving the Pt-like activity for the hydrogen peroxid reduction reaction. Importantly, at certain cathodic potential, only reduction reaction of hydrogen peroxide occurs at the Pt-NCs surface. Consequently, the phosphonate functionalized Pt-NCs can be used to fabricate a new kind of hydrogen peroxide electrochemical sensor with high performance in the presence of oxygen. Under optimized experimental conditions, the hydrogen peroxide electrochemical sensor shows fast response (less than 2s) and wide linear range (1.0×10−6–1.0×10−3M) in the presence of oxygen. The results presented here indicate an important new direction in the quest to design selective catalysts for the fabrication of noble-metal based H2O2 electrochemical sensor.

Selective catalysts for the hydrogen oxidation and oxygen reduction reactions by patterning of platinum with calix[4]arene molecules

The design of new catalysts for polymer electrolyte membrane fuel cells must be guided by two equally important fundamental principles: optimization of their catalytic behaviour as well as the long-term stability of the metal catalysts and supports in hostile electrochemical environments. The methods used to improve catalytic activity are diverse, ranging from the alloying and de-alloying of platinum to the synthesis of platinum core-shell catalysts. However, methods to improve the stability of the carbon supports and catalyst nanoparticles are limited, especially during shutdown (when hydrogen is purged from the anode by air) and startup (when air is purged from the anode by hydrogen) conditions when the cathode potential can be pushed up to 1.5 V (ref. 11). Under the latter conditions, stability of the cathode materials is strongly affected (carbon oxidation reaction) by the undesired oxygen reduction reaction (ORR) on the anode side. This emphasizes the importance of designing selective anode catalysts that can efficiently suppress the ORR while fully preserving the Pt-like activity for the hydrogen oxidation reaction. Here, we demonstrate that chemically modified platinum with a self-assembled monolayer of calix[4]arene molecules meets this challenging requirement.

The melanophore aggregating response of isolated fish scales: a very rapid and sensitive diagnosis of whooping cough

Pertussis toxin (PT) has been found to block noradrenaline-induced pigment aggregation in fish melanophores, and, based on this, a rapid and highly sensitive assay for PT was developed. Some preliminary results have also indicated that it may be possible to detect PT-like activity in saliva samples from patients with clinically suspected pertussis. In the present study the diagnostic value of the fish melanophore method was evaluated in 70 patients suspected of having pertussis; culture, serology and physician diagnosis were used as reference methods. In 60 of the patients, pertussis was verified by at least one of the reference methods. The melanophore test showed PT-like activity in saliva samples from 58 of the patients. Three patients with reference-verified pertussis showed no PT-like activity in the test; among these, one patient had been immunized and had also been treated with erythromycin during 3 days immediately prior to visiting the hospital. The melanophore test has three major advantages: it allows detection of pertussis in the early and curable stage of the disease; it takes only 2 h to perform; and it requires no sophisticated equipment.

A rapid and sensitive assay for pertussis toxin based on pigment aggregation within the melanophores of an isolated fish scale

The noradrenaline-induced pigment aggregation within the melanophores of the cuckoo wrasse (Labrus ossifagus L.) has been shown to be mediated by postsynaptic alpha2-adrenoceptors which in turn act via an inhibitory control of adenylate cyclase. In a previous paper it was shown that pertussis toxin (PT) caused a blockade of noradrenaline-induced pigment aggregation. Based on these findings, an assay for PT has been developed. The method involves toxin titration directly on isolated fish scales from L. ossifagus, takes about 2 h to perform and needs no sophisticated equipment. The method allows detection of femtogram quantities of toxin per ml. The effect of purified PT was neutralized by antiserum. Some preliminary results indicate that it is possible to detect PT-like activity in sputum samples from patients with suspected whooping cough, whereas no PT-like activity could be detected in samples from healthy volunteers.