High performance electrocatalysts supported on graphene based hybrids for polymer electrolyte membrane fuel cells

In this study, new electrocatalysts for PEM fuel cells, based on Pt nanoparticles supported on hybrid carbon support networks comprising reduced graphene oxide (rGO) and carbon black (CB) at varying ratios, were designed and prepared by means of a rapid and efficient microwave-assisted synthesis method. Resultant catalysts were characterized ex-situ for their structure, morphology, electrocatalytic activity. In addition, membrane-electrode assemblies (MEAs) fabricated using resultant electrocatalysts and evaluated in-situ for their fuel cell performance and impedance characteristics. TEM studies showed that Pt nanoparticles were homogeneously decorated on rGO and rGO-CB hybrids while they had bigger size and partially agglomerated distribution on CB. The electrocatalyst, supported on GO-CB hybrid containing 75% GO (HE75), possessed very encouraging results in terms of Pt particle size and dispersion, catalytic activity towards HOR and ORR, and fuel cell performance. The maximum power density of 1090 mW cm(-2) was achieved with MEA (Pt loading of 0.4 mg cm(-2)) based on electrocatalyst, HE75. Therefore, the resultant hybrid demonstrated higher Pt utilization with enhanced FC performance output. Our results, revealing excellent attributes of hybrid supported electrocatalysts, can be ascribed to the role of CB preventing rGO sheets from restacking, effectively modifying the array of graphene and providing more available active catalyst sites in the electrocatalyst material.(C) 2018 The Authors

What is missing in autonomous discovery: Open challenges for the community

Self-driving labs (SDLs) leverage combinations of artificial intelligence, automation, and advanced computing to accelerate scientific discovery. The promise of this field has given rise to a rich community of passionate scientists, engineers, and social scientists, as evidenced by the development of the Acceleration Consortium and recent Accelerate Conference. Despite its strengths, this rapidly developing field presents numerous opportunities for growth, challenges to overcome, and potential risks of which to remain aware. This community perspective builds on a discourse instantiated during the first Accelerate Conference, and looks to the future of self-driving labs with a tempered optimism. Incorporating input from academia, government, and industry, we briefly describe the current status of self-driving labs, then turn our attention to barriers, opportunities, and a vision for what is possible. Our field is delivering solutions in technology and infrastructure, artificial intelligence and knowledge generation, and education and workforce development. In the spirit of community, we intend for this work to foster discussion and drive best practices as our field grows

Precisely controlled synthesis of reduced graphene oxide supported electrocatalysts for PEM fuel cells by pulsed photocatalytic deposition

It has almost been a decade that scientists have been trying to address the shortcomings of batteries and polymer electrolyte membrane (PEM) fuel cells in production cost. One of the most important parts of the PEM fuel cells is its catalyst layer, CL. The CL of PEM fuel cells consists of Pt-based particles deposited on a carbon support. Although carbon black (CB)/Pt shows a promising electrochemical performance for hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR), its vulnerability to the PEM fuel cells’ harsh environment has made this carbon-based electrocatalysts very sensitive to corrosion, and performance loss. One of the promising candidates to replace carbon black in CL preparation seemed to be graphene-based support. This study demonstrated the capability of a novel method in controlling the structural and electrochemical properties of electrocatalysts deposited on graphene-based supports, utilizing a pulsed-UV setup for the synthesis procedure. In the second chapter, the variation of UVon and UVoff periods resulted in samples with a range of different structures, compositions, and activities. The results revealed a dominant growth and agglomeration phase of Pt particles, mostly with metallic states, by increasing both UVon and Uoff time spontaneously. Further chemical reduction by highly concentrated ascorbic acid was used to confirm proposed mechanisms, which lead to samples even with more metallic Pt (Pt0) and higher electrochemical activities. The rest of the second chapter focused on utilizing a series of transition metal ions, Co2+, Ni2+ or Fe2+, to assist the deposition of Pt on PRGO planes that resulted in various types of Pt particles size, morphologies and distribution. Different interactions between hole scavengers and PRGO particles or water molecules, was the main parameter that modulated the Pt4+ reduction. The structural and electrochemical properties of electrocatalysts revealed that utilizing the cobalt-based hole scavenger, caused a dominant growth phase of Pt particles at preferred positions, with improved electrocatalytic activities (ECSA value of 195.91 m2.g-1 for Co2+ vs. 152.01 m2.g-1 for methanol). The third chapter includes the computational methods in evaluating the properties of the samples by modelling either the cyclic voltammetry data with a neural network algorithm or DFT calculation of H2 adsorption on graphene-based electrocatalysts. The result of the neural network modelling demonstrated the potential of the proposed method in designing a highly controllable synthesis procedure by which the electrochemical properties of the electrocatalysts could be predictable before the synthesis. The DFT calculation by the Quantum-Espresso code revealed that the existence of oxygen functional groups on graphene plane not only affects the crystal structure of deposited Pt particles, but also hinders the adsorption of H2 molecules on Pt surface

The correlation among deposition parameters, structure and corrosion behaviour of ZnNi/nano-SiC composite coating deposited by pulsed and pulsed reverse current

The present work shows how the parameters of pulsed current (PC) deposition affect structural and morphological characteristics of electrodeposited ZnNi/nano-SiC composite coating and its corrosion properties. In this regard, ZnNi coatings containing SiC nanoparticles were electrodeposited from chloride bath by PC and pulsed reverse current (PRC) methods, and the effect of duty cycle, frequency and reverse current density were studied. With low and high duty cycles the SiC content of the coating was more than the coating deposited by medium duty cycle. Changing the duty cycle affected the coating composition, structure and morphology. Elevation of the pulse frequency increased SiC content of the coating. Application of PRC produced a coating with a complex and dendritic structure. In most of the electrodeposition conditions, in addition to direct effects of PC on coatings characteristics, it was seen that the more SiC was deposited in the coating the less Ni was deposited, and this also affected the corrosion behaviour. The best corrosion resistance behaviour was shown by coatings with more compact structure and less porosity

The correlation among deposition parameters, structure and corrosion behaviour of ZnNi/nano-SiC composite coating deposited by pulsed and pulsed reverse current

The present work shows how the parameters of pulsed current (PC) deposition affect structural and morphological characteristics of electrodeposited ZnNi/nano-SiC composite coating and its corrosion properties. In this regard, ZnNi coatings containing SiC nanoparticles were electrodeposited from chloride bath by PC and pulsed reverse current (PRC) methods, and the effect of duty cycle, frequency and reverse current density were studied. With low and high duty cycles the SiC content of the coating was more than the coating deposited by medium duty cycle. Changing the duty cycle affected the coating composition, structure and morphology. Elevation of the pulse frequency increased SiC content of the coating. Application of PRC produced a coating with a complex and dendritic structure. In most of the electrodeposition conditions, in addition to direct effects of PC on coatings characteristics, it was seen that the more SiC was deposited in the coating the less Ni was deposited, and this also affected the corrosion behaviour. The best corrosion resistance behaviour was shown by coatings with more compact structure and less porosity

A Continuous-flow Photocatalytic Reactor for the Precisely Controlled Deposition of Metallic Nanoparticles

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic nanoparticles is developed. Guidelines for the replication of the reactor and its operation are provided in detail. Three different composite systems (Pt/graphene, Pt/TiO2, and Au/TiO2) with monodisperse and uniformly distributed particles are produced by this reactor, and the photodeposition mechanism, as well as the synthesis optimization strategy, are discussed. The synthesis methods and their technical aspects are described comprehensively. The role of the ultraviolet (UV) dose (in each excitation pulse) on the photodeposition process is investigated and the optimum values for each composite system are provided

Platinum nanoparticles loaded carbon black: reduced graphene oxide hybrid platforms for label-free electrochemical DNA and oxidative DNA damage sensing

Carbon black-based hybrid materials have attracted great attention in the design of electrochemical sensors due to their consistent electroanalytical properties. With this in mind, for the first time, we present the preparation of platinum nanoparticles loaded carbon black:reduced graphene oxide (PtNPs/CB:rGO) hybrid platforms for label-free electrochemical DNA and DNA damage sensing. Synthesis of different hybrids was performed via microwave-assisted reduction method for the impregnation of platinum nanoparticles efficiently. These materials were characterized with X-ray diffraction analysis (XRD), Raman spectroscopy, transmission emission spectroscopy (TEM) and subsequently they were used for pencil graphite electrode modification in order to improve the characteristics of the surface. Modified electrodes were firstly applied for fish sperm DNA (fsDNA) analysis. The effect of different ratios (wt.:wt. %) of CB and rGO was investigated and it was shown that the hybrid material with 50:50 ratio had better sensitivity with a low detection limit of 0.14 mg L−1 and a good linearity to fsDNA between 1 and 200 mg L−1 (n = 3) based on guanine (G) oxidation by using differential pulse voltammetry (DPV). In order to expand this comparison, PtNPs/CB and PtNPs/rGO modified electrodes were also incorporated. Furthermore, the electroanalytical response of the hybrid material modified electrode was investigated based on the oxidation of thymine (T). Later on, oxidative DNA damage detection in the presence of Cu(II)/H2O2 reagents and protection studies in the presence of ascorbic acid were performed successfully by using electrochemical impedance spectroscopy (EIS). The study pointed out the remarkable reproducibility and sensitivity of the CB-based modification for nanoparticle decoration