Adrian C. Fisher

Vertically oriented MoS2 and WS2 nanosheets directly grown on carbon cloth as efficient and stable 3-dimensional hydrogen-evolving cathodes

The development of non-noble-metal based hydrogen-evolving catalysts is essential to the practical application of water-splitting devices. Improvement of both the activity and stability of such catalysts remains a key challenge. In this work, a simple solvothermal method is developed to directly grow MoS2 and WS2 on carbon cloth with vertically oriented nanosheet layers. With the unique layer orientation that maximally exposes active edge sites as well as a rapid release of small gas bubbles to maintain a large working area, such prepared 3-dimensional electrodes exhibit high activity towards the HER. In addition, they also exhibit prominent electrochemical durability, thanks to the strong bonding between the nanosheet layers and the substrate along with the self-removal of the as-formed H2 bubbles from the nano-porous electrode surface.

Locoregional recurrences are frequent after radiofrequency ablation for hepatocellular carcinoma

BACKGROUND Enthusiasm for radiofrequency ablation (RFA) therapy for patients with unresectable hepatocellular carcinoma (HCC) has increased. The data for recurrence after RFA for patients with HCC is not well documented. The purpose of this study was to evaluate tumor recurrence patterns after RFA in patients with unresectable HCC. STUDY DESIGN Over a 3-year period, 50 patients having RFA for unresectable HCC were identified at a single institution. Medical records and radiologic studies were reviewed and outcomes factors analyzed. RESULTS Of the entire cohort, 46 patients underwent RFA by a percutaneous approach under CT guidance. Most patients underwent either one (n = 22) or two ablations (n = 23). At the time of this report, 14 patients (28%) were tumor-free by radiologic and biochemical (alpha-fetoprotein) parameters. Eighteen additional patients had persistence of tumor at the ablation site and 14 patients had recurrence in the liver at sites different from the ablation site. An additional four patients had recurrence in extrahepatic sites. Twelve patients underwent orthotopic liver transplantation after RFA. Of these 12, 5 (42%) demonstrated no viable tumor in the explanted liver. Independent predictors of tumor recurrence included tumor size, serum AFP levels, and the presence of hepatitis. CONCLUSIONS These data suggest that factors such as tumor size should be considered before employing RFA therapy. In addition to treating the primary tumor, other therapies aimed at the livers inflammatory state might also be important in achieving a durable response after RFA.

A Flexible Electrode Based on Iron Phosphide Nanotubes for Overall Water Splitting

The design of cheap and efficient water splitting systems for sustainable hydrogen production has attracted increasing attention. A flexible electrode, based on carbon cloth substrate and iron phosphide nanotubes coated with an iron oxide/phosphate layer, is shown to catalyze overall water splitting. The as-prepared flexible electrode demonstrates remarkable electrocatalytic activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) at modest overpotentials. The surface iron oxide/phosphate, which is formed in situ, is proposed to improve the HER activity by facilitating the water-dissociation step and serves directly as the catalytically-active component for the OER process.

Photosynthetic biofilms in pure culture harness solar energy in a mediatorless bio-photovoltaic cell (BPV) system

Microbial fuel cells are an emerging technology for converting organic substrates into electrical power. Recent research has shown that biofilms of some bacterial species are capable of self-mediated extracellular electron transfer. The prospect of exploiting this trait in photoautotrophic microbes that do not require an organic substrate has important implications for the future development of renewable solar energy technologies. Here we report on light-driven electrical power generated with biofilms grown from photosynthetic fresh water or marine species without the addition of an artificial electron-shuttling mediator. Green alga (Chlorella vulgaris, Dunaliella tertiolecta) or cyanobacteria (Synechocystis sp. PCC 6803, Synechococcus sp. WH 5701) strains were grown directly on a transparent, conductive anode (indium tin oxide-coated polyethylene terephthalate) and power generation under light and dark conditions was evaluated using a single-chamber bio-photovoltaic cell (BPV) system. Increased power outputs were observed for all strains upon illumination, with the largest light effect observed for Synechococcus (maximum 10.3 mW m−2 total power output recorded under 10 W m−2 white light). Further experiments conducted with Synechococcus and C. vulgaris showed that photosynthetic oxygen evolution rates were consistent with BPV power outputs under different light regimes (red, green and blue light), indicating a direct link between power output and photosynthetic activity. Biofilm power generation in these BPV devices was self-sustained for several weeks and was highly sensitive to ambient light levels. When connected in series, four BPVs (each 0.011 m2) generated enough power to run a commercial digital clock.

Surface Segregation in Bimetallic Nanoparticles: A Critical Issue in Electrocatalyst Engineering

Bimetallic nanoparticles are a class of important electrocatalyst. They exhibit a synergistic effect that critically depends on the surface composition, which determines the surface properties and the adsorption/desorption behavior of the reactants and intermediates during catalysis. The surface composition can be varied, as nanoparticles are exposed to certain environments through surface segregation. Thermodynamically, this is caused by a difference in surface energy between the two metals. It may lead to the enrichment of one metal on the surface and the other in the core. The external conditions that influence the surface energy may lead to the variation of the thermodynamic steady state of the particle surface and, thus, offer a chance to vary the surface composition. In this review, the most recent and important progress in surface segregation of bimetallic nanoparticles and its impact in electrocatalysis are introduced. Typical segregation inducements and surface characterization techniques are discussed in detail. It is concluded that surface segregation is a critical issue when designing bimetallic catalysts. It is necessary to explore methods to control it and utilize it as a way towards producing robust, bimetallic electrocatalysts.

Strategies on the Design of Nitrogen-Doped Graphene.

Substitutional nitrogen doping in graphene has been a very powerful tool to tailor the pristine property of graphene and furthermore extend its application. While nitrogen-doped graphene (N-graphene) has shown many potential applications in catalysis, electronics, sensors and so on, there is still a lack of accurate control of substitutional nitrogen doping, and higher performance toward various applications is always needed. This Perspective summarizes the ongoing developments toward better control of nitrogen doping. Moreover, two recent strategies aiming to promote the activity of N-graphene are also discussed.

Construction of Efficient 3D Gas Evolution Electrocatalyst for Hydrogen Evolution: Porous FeP Nanowire Arrays on Graphene Sheets

A novel 3D hierarchical nanocomposite of vertically aligned porous FeP nanowires on reduced graphene oxide is prepared as a demonstration of constructing an efficient hydrogen evolution catalyst. Extension of this nanostructuring strategy to other functional nanocomposites by combining different dimensional nanomaterials is attractive.

Voltammetry at C60-modified electrodes

Abstract The reduction of electrodes coated with C 60 -fullerene is examined in acetonitrile solution containing a wide variety of supporting electrolytes (MClO 4 ; M = Li, Na, Ba 0.5 , NR 4 ). Electrochemical intercalation is observed with the formation of fulleride salts. Intercalation is typically irreversible except for the case of R = n -butyl where stable coats of fullerides may be formed into which charge can be passed with near chemical reversibility. Electron-transfer reactions at electrodes modified with C 60 coatings were investigated for diverse substrates. With unreduced coats impeded diffusion to the metal surface was seen, whereas with films reduced in the presence of tetrabutylammonium perchlorate coat-mediated electron transfer to the substrate was possible.

The transport limited currents at insonated electrodes

We investigate the transport limited currents (ILim) observed at electrodes placed ‘face-on’ to a sonic transducer such that a significant convective flux arising from acoustic streaming is observed. Experiments conducted at 25 kHz with turbulent solution flow concerned with the oxidations of iodide or ferrocyanide and the reductions of ruthenium hexammine(III) or the hydrogen ion, all in aqueous solution, over a wide range of conditions, including those of variable kinematic viscosity (υ) controlled by the addition of sucrose to the electrolyte solution and changing ultrasound power (Pw) are used to show that the following equation accurately predicts the observed limiting currents, ILim = C(h,υ)D2/3ACbulkPw1/2 where A is the electrode area, Cbulk is the concentration of the redox active species, D is the diffusion coefficient, and C is a function of υ and of the electrode-to-horn separation, h which falls off strongly as h increases.

Enhanced methane yields from anaerobic digestion of Arthrospira maxima biomass in an advanced flow-through reactor with an integrated recirculation loop microbial fuel cell.

A semi-continuously fed continuous stirred tank reactor (CSTR), advanced flow-through anaerobic reactor (AAR) and advanced flow-through anaerobic digester with an integrated recirculation loop microbial fuel cell (ADMFC) were investigated for the production of methane using Arthrospira maxima as the sole feedstock. The study demonstrated that the inclusion of a recirculation loop MFC increased the methane yields and so energy efficiency of anaerobic digestion of Arthrospira maxima biomass. The semi-continuously fed CSTR operating under a hydraulic retention time (HRT) of 10 days and an organic loading rate (OLR) of 0.5 g DW per L−1 d−1 concluded a maximum methane yield of 90 ± 19 mL CH4 per g VS with an energy efficiency of 17.1 ± 0.8%. The continuous phase AAR and ADMFC units were operated with HRTs ranging from 2 to 4 days and organic loading rates varying from 0.5 to 3 g DW L−1 d−1. The maximum methane yield and energy efficiency concluded from the ADMFC unit was 173 ± 38 mL CH4 per g VS and 29.7 ± 6.8% respectively, whilst that of the AAR was 136 ± 16 mL CH4 per g VS and 22.1 ± 2.6%.