Free-Standing 3D Hierarchical Carbon Foam-Supported PtCo Nanowires with “Pt Skin” as Advanced Electrocatalysts

Ultrafast synthesis of efficient TS-PtCoCu/CNTs composite with high feed-to-product conversion rate by Joule heating for electrocatalytic oxidation of ethanol

Due to the challenges involved in achieving high metal load, uniform metal dispersion and nanosized metal particles simultaneously, it is difficult to develop a simple protocol for the rapid and efficient synthesis of Pt-based composites for electrocatalytic ethanol oxidation reaction (EOR). In this study, a facile ultrafast thermal shock strategy via Joule heating was applied to fabricate a series of PtCoCu ternary nanoalloys decorated carbon nanotube composites (TS-PtCoCu/CNTs), without the need for a reducing agent or surfactant. The TS-PtCoCu/CNTs with optimal Pt content (∼15 %) exhibited excellent EOR activity, with mass and specific activity of 3.58 A mgPt-1 and 5.79 mA cm-2, respectively, which are 3.8 and 13.5 times higher than those of Pt/C. Compared with the control prepared through the traditional furnace annealing, the catalyst also showed excellent activity and stability. DFT calculations revealed that the TS-PtCoCu/CNTs possesses a downshifted d-band center, weakened CO adsorption and higher OH affinity compared with monometallic Pt, all of which lead to the preferred C1 pathway for EOR. This study demonstrates an ultrafast construction of a highly efficient Pt-Co-Cu ternary catalyst for EOR. Additionally, it provides insights into the reaction mechanism based on structural characterization, electrochemical characterization, and theoretical calculations.

Pt-Co Electrocatalysts: Syntheses, Morphologies, and Applications

Pt-Co electrocatalysts have attracted significant attention because of their excellent performance in many electrochemical reactions. This review focuses on Pt-Co electrocatalysts designed and prepared for electrocatalytic applications. First, the various synthetic methods and synthesis mechanisms are systematically summarized; typical examples and core synthesis parameters are discussed for regulating the morphology and structure. Then, starting with the design and structure-activity relationship of catalysts, the research progress of the morphologies and structures of Pt-Co electrocatalysts obtained based on various strategies, the structure-activity relationship between them, and their properties are summarized. In addition, the important electrocatalytic applications and mechanisms of Pt-Co catalysts, including electrocatalytic oxidation/reduction and bifunctional catalytic reactions, are described and summarized, and their high catalytic activities are discussed on the basis of their mechanism and active sites. Moreover, the advanced electrochemical in situ characterization techniques are summarized, and the challenges and direction concerning the development of high-performance Pt-Co catalysts in electrocatalysis are discussed.

Recent Developments for the Application of 3D Structured Material Nickel Foam and Graphene Foam in Direct Liquid Fuel Cells and Electrolyzers

Platinum and platinum-based catalysts are some of the most effective catalysts used in fuel cells. However, electrocatalysts used for direct liquid fuel cells (DLFCs) and electrolyzers are high cost and suffer from several other problems, thus hindering their commercialization as power sources to produce clean energy. Common issues in electrocatalysts are low stability and durability, slow kinetics, catalyst poisoning, high catalyst loading, high cost of the catalytic materials, poisoning of the electrocatalysts, and formation of intermediate products during electrochemical reactions. The use of catalyst supports can enhance the catalytic activity and stability of the power sources. Thus, nickel foam and graphene foam with 3D structures have advantages over other catalyst supports. This paper presents the application of nickel foam and graphene foam as catalyst supports that enhance the activities, selectivity, efficiency, specific surface area, and exposure of the active sites of DLFCs. Selected recent studies on the use of foam in electrolyzers are also presented.

Recent advances in formic acid electro-oxidation: from the fundamental mechanism to electrocatalysts

Direct formic acid fuel cells have attracted significant attention because of their low fuel crossover, high safety, and high theoretical power density among all the proton-exchange membrane fuel cells. Much effort has been devoted to the study of formic acid oxidation, including the reaction processes and electrocatalysts. However, as a model reaction, the anodic electro-oxidation process of formic acid is still not very clear, especially regarding the confirmation of the intermediates, which is not helpful for the design and synthesis of high-performance electrocatalysts for formic acid oxidation or conducive to understanding the reaction mechanisms of other small fuel molecules. Herein, we briefly review the recent advances in investigating the mechanism of formic acid electro-oxidation and the basic design concepts of formic acid oxidation electrocatalysts. Rather than an exhaustive overview of all aspects of this topic, this mini-review mainly outlines the progress of this field in recent years.

Insights into the morphology and composition effects of one-dimensional CuPt nanostructures on the electrocatalytic activities and methanol oxidation mechanism by in situ FTIR

Morphology modulation and surface structure-controlled synthesis are two effective ways to tune the electrocatalytic activities of metal nanomaterials. Pt-based binary or ternary metal nanostructures have become a class of promising catalysts toward the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) for direct methanol fuel cells. Herein to reveal the morphology and surface structure effects of one-dimensional (1D) Pt-based nanostructures on their electrocatalytic properties, two types of 1D CuPt nanowires (CuPt NWs) and CuPt nanotubes (CuPt NTs) with tunable surface structures and compositions were fabricated using a convenient and easy strategy. It was found that among all the studied samples, CuPt2.22 NWs exhibited the highest efficiency catalytic performances for both the ORR and MOR in an acidic electrolyte. For the ORR, CuPt2.22 NWs exhibited an onset potential (Eonset) of 0.749 V and a half-wave potential (E1/2) of 0.577 V, which are more positive than those of the commercial Pt/C (0.668 V and 0.558 V). On the other hand, CuPt2.22 NWs show a specific activity of 20.76 mA cm-2 and a mass activity of 0.171 mA μgPt-1 for the MOR, which are 7.75 and 1.82 times, respectively, larger than those of Pt/C (2.679 mA cm-2 and 0.094 mA μgPt-1). Meanwhile, the reaction mechanism of the MOR on CuPt2.22 NWs was examined by in situ FTIR. From the enhanced IR absorption, the linear- and bridge-adsorbed CO intermediates can be determined during the methanol oxidation on CuPt2.22 NWs, from which the MOR proceeds through a dual reaction pathway. This work reveals that rationally tuning the electronic structures of 1D metal nanomaterials by well-controlling the composition and surface morphology on the nanoscale could greatly enhance the catalytic properties, which are very important for their application in fuel cells.

Shape-control of one-dimensional PtNi nanostructures as efficient electrocatalysts for alcohol electrooxidation

Bimetallic one-dimensional (1D) nanostructures such as nanowires (NWs) and nanorods (NRs), serving as high-efficiency anode electrocatalysts, have attracted extensive attention in the past decade. However, the precise design and synthesis of 1D Pt-based nanocrystals with tunable morphology and size still remain an arduous challenge. Driven by this, we report a facile yet efficient strategy for the first time to prepare PtNi ultrafine NWs (UNWs), sinuous NWs (SNWs) and ultrashort NRs (UNRs) by adjusting the amount of citric acid, ascorbic acid and glucose. Detailed analysis of their electrocatalytic properties has indicated that the as-obtained PtNi SNWs exhibit the most outstanding electrocatalytic activity toward ethylene glycol oxidation reaction (EGOR) and glycerol oxidation (GOR), 4.5 and 4.3 times higher in mass activity as well as 4.3 and 3.9 times higher in specific activity compared with the commercial Pt/C catalyst. The as-prepared PtNi SNWs are also more stable than the commercial Pt/C catalyst after successive durability tests. The proposed method provides insight into more rational designs of bimetallic nanocatalysts with 1D architectures and the as-synthesized PtNi catalysts with improved electrocatalytic performance assist in promoting the further development of direct alcohol fuel cells (DAFCs).

Direct synthesis of bimetallic PtCo mesoporous nanospheres as efficient bifunctional electrocatalysts for both oxygen reduction reaction and methanol oxidation reaction

The engineering of electrocatalysts with high performance for cathodic and/or anodic catalytic reactions is of great urgency for the development of direct methanol fuel cells. Pt-based bimetallic alloys have recently received considerable attention in the field of fuel cells because of their superior catalytic performance towards both fuel molecule electro-oxidation and oxygen reduction. In this work, bimetallic PtCo mesoporous nanospheres (PtCo MNs) with uniform size and morphology have been prepared by a one-step method with a high yield. The as-made PtCo MNs show superior catalytic activities for both oxygen reduction reaction and methanol oxidation reaction relative to Pt MNs and commercial Pt/C catalyst, attributed to their mesoporous structure and bimetallic composition.

Uniformly dispersed platinum-cobalt alloy nanoparticles with stable compositions on carbon substrates for methanol oxidation reaction

Alloying platinum (Pt) with suitable transition metals is effective way to enhance their catalytic performance for methanol oxidation reaction, and reduce their cost at mean time. Herein, we report our investigation on the synthesis of bimetallic platinum-cobalt (PtCo) alloy nanoparticles, their activation, as well as the catalytic evaluation for methanol oxidation reaction. The strategy starts with the synthesis of PtCo alloy nanoparticles in an organic medium, followed by loading on carbon substrates. We then remove the capping agent by refluxing the carbon-supported PtCo particles in acetic acid before electrochemical measurements. We emphasize the change in composition of the alloys during refluxing process, and the initial PtCo alloys with Pt/Co ratio of 1/2 turns into stable alloys with Pt/Co ratio of 3/1. The final Pt₃Co particles have uniform distribution on carbon substrates, and exhibit activity with 2.4 and 1.5 times of that for commercial Pt/C and PtRu/C for methanol oxidation reaction.

Branched PdAu nanowires with superior electrocatalytic formic acid oxidation activities

Branched PdAu nanowires supported on graphene were prepared as catalysts for formic acid electro-oxidation, and they exhibited higher catalytic activity and durability than Pd/graphene and commercial Pd/C catalysts.

Silica-polydopamine core–shell self-confined templates for ultra-stable hollow Pt anchored N-doped carbon electrocatalysts

We present the use of silica-polydopamine (SiO₂@PDA) core–shell nanoparticles (NPs) as self-confined templates for the fabrication of ultra-stable hollow Pt anchored N-doped carbon nanospheres (Pt/HN-C).

A polyacrylonitrile copolymer-silica template for three-dimensional hierarchical porous carbon as a Pt catalyst support for the oxygen reduction reaction

Herein, we report a novel route to construct a hierarchical three-dimensional porous carbon (3DC) through a copolymer-silica assembly.

3D nanoporous gold scaffold supported on graphene paper: Freestanding and flexible electrode with high loading of ultrafine PtCo alloy nanoparticles for electrochemical glucose sensing

Recent advances in on-body wearable medical apparatus and implantable devices drive the development of light-weight and bendable electrochemical sensors, which require the design of high-performance flexible electrode system. In this work, we reported a new type of freestanding and flexible electrode based on graphene paper (GP) supported 3D monolithic nanoporous gold (NPG) scaffold (NPG/GP), which was further modified by a layer of highly dense, well dispersed and ultrafine binary PtCo alloy nanoparticles via a facile and effective ultrasonic electrodeposition method. Our results demonstrated that benefited from the synergistic effect of the electrocatalytically active PtCo alloy nanoparticles, the large-active-area and highly conductive 3D NPG scaffold, and the mechanically strong and stable GP electrode substrate, the resultant PtCo alloy nanoparticles modified NPG/GP (PtCo/NPG/GP) exhibited high mechanical strength and good electrochemical sensing performances toward nonenzymatic detection of glucose, including a wide linear range from 35 μM- to 30 mM, a low detection limit of 5 μM (S/N = 3) and a high sensitivity of 7.84 μA cm(-2) mM(-1) as well as good selectivity, long-term stability and reproducibility. The practical application of the proposed PtCo/NPG/GP has also been demonstrated in in vitro detection of blood glucose in real clinic samples.

Gold nanosheets synthesized with red marine alga Actinotrichia fragilis as efficient electrocatalysts toward formic acid oxidation

In this study, gold nanosheets were synthesized with red marine alga (Actinotrichia fragilis) collected from Persian Gulf and used as an electrocatalyst for oxidation of formic acid.