The voltammetry of Pt{111}, Pt{100}, Pt{110} and Pt{311} single crystal electrodes as a function of perchloric acid concentration (0.05-2.00 M) has been studied in order to test the assertion made in recent reports by Watanabe et al. that perchlorate anions specifically adsorb on polycrystalline platinum. Such an assertion would have significant ramifications for our understanding of electrocatalytic processes at platinum surfaces since perchlorate anions at low pH have classically been assumed not to specifically adsorb. For Pt{111}, it is found that OHad and electrochemical oxide states are both perturbed significantly as perchloric acid concentration is increased. We suggest that this is due to specific adsorption of perchlorate anions competing with OHad for adsorption sites. The hydrogen underpotential deposition (H UPD) region of Pt{111} however remains unchanged although evidence for perchlorate anion decomposition to chloride on Pt{111} is reported. In contrast, for Pt{100} no variation in the onset of electrochemical oxide formation is found nor any shift in the potential of the OHad state which normally results from the action of specifically adsorbing anions. This suggests that perchlorate anions are non-specifically adsorbed on this plane although strong changes in all H UPD states are observed as perchloric acid concentration is increased. This manifests itself as a redistribution of charge from the H UPD state situated at more positive potential to the one at more negative potential. For Pt{110} and Pt{311}, marginal changes in the onset of electrochemical oxide formation are recorded, associated with specific adsorption of perchlorate. Specific adsorption of perchlorate anions on Pt{111} is deleterious to electrocatalytic activity in relation to the oxygen reduction reaction (ORR) as measured using a rotating disc electrode (RDE) in a hanging meniscus configuration. This study supports previous work suggesting that a large component of the ORR activity on platinum is governed by simple site blocking by specifically adsorbed anions and/or electrosorbed oxide.

Riverine fish are subjected to heterogeneous flow velocities and turbulence and may use this to their advantage by selecting regions that balance energy expenditure for station holding while maximizing energy gain through feeding opportunities. This study investigated microhabitat selection by guppies Poecilia reticulata in terms of flow characteristics generated by hemisphere boulders in an open channel flume. Velocity and turbulence influenced the variation in swimming behaviour with respect to size, sex and parasite intensity. With increasing body length, fish swam further and more frequently between boulder regions. Larger guppies spent more time in the areas of high-velocity and low-turbulence regions beside the boulders, whereas smaller guppies frequented the low-velocity and high-turbulence regions directly behind the boulders. Male guppies selected the regions of low velocity, indicating possible reduced swimming ability owing to hydrodynamic drag imposed by their fins. With increasing Gyrodactylus turnbulli burden, fish spent more time in regions with moderate velocity and lowest turbulent kinetic energy which were the most spatially and temporally homogeneous in terms of velocity and turbulence. These findings highlight the importance of heterogeneous flow conditions in river channel design owing to the behavioural variability within a species in response to velocity and turbulence.

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The irreversible adsorption of polyvinylpyrrolidone (PVP) on a series of well-defined platinum single crystal electrode surfaces has been investigated using voltammetry, ex situ XPS and DFT calculations. It is found that the adsorption of PVP is highly structure sensitive with strong adsorption exhibited by step and {100} terrace sites with only weak interactions observed between PVP and Pt{111} terraces, at least at low PVP surface concentrations. Subsequent investigations using CO electrooxidation confirmed that blocking of platinum surface sites by PVP toward CO chemisorption was marked for Pt{100} terraces but hardly occurred at all at Pt{111} terraces. Density Functional Theory calculations also confirmed that the monomer of PVP interacts more strongly with Pt{100} compared to Pt{111} sites (−142 and −125 kJ mol −1 respectively). Ex situ XPS studies suggested that the main PVP−Pt interaction is associated with charge transfer from the carbonyl substituent of PVP toward the metal surface in accordance with earlier studies of PVP adsorbed on polycrystalline platinum surfaces. Irreversible adsorption of Pt adatoms onto Pt{hkl} surfaces with and without PVP−surface modification demonstrated a marked preference for {100} facet formation on Pt{100} surfaces but no corresponding preferential {111} facet growth on Pt{111} when PVP was present. Hence, the shape control exhibited by PVP in expediting the formation of cubic Pt nanoparticles is explicitly confirmed as arising from relatively weak PVP chemisorption on Pt{111} facets at low PVP surface loading.

Two polymers (i) the polymer of intrinsic microporosity (or PIM) ethanoanthracene TB-PIM (P1, PIM-EA-TB, MW 70 kDa, BET surface area 1027 m 2 g-1) and (ii) the structurally less rigid polymer based on dimethyldiphenylmethane units (P2, BDMPM-TB, MW 100 kDa, BET surface area 47 m 2 g-1) are compared to highlight the benefits of the newly emerging PIM membrane materials in electrocatalysis and nanostructure formation. Binding sites and binding ability/capacity in aqueous environments are compared in films deposited onto glassy carbon electrodes for (i) indigo carmine dianion immobilisation (weakly binding from water-ethanol) and (ii) PdCl4 2immobilisation (strongly binding from acidic media). Nano-lamella growth for Pd metal during electro-reduction of PdCl4 2is observed. Electrocatalytic oxidation of formic acid (at pH 6) is investigated for P1 and P2 as a function of film thickness. The more rigid high BET surface area PIM material P1 exhibits "openpore" characteristics with much more promising electrocatalytic activity at Pd lamella within polymer pores.