The wide possibilities of l-cysteine and l-cystine adsorbed and/or oxidized species onto Pt were explored by FTIR experiments and DFT calculations.

The current electrochemical method for H2 production is water electrolysis, a process with a high energy demand, which is limited by the oxygen evolution reaction (OER). One way to handle the problems related to the OER is to use other oxidative reactions by so-called coupled water electrolysis. One option is the SO2 oxidation reaction (SO2OR), a process that generates H2SO4, which has industrial use, by the consumption of an abundant pollutant that demands, under standard conditions, 0.70 V less than the OER according to theoretical predictions. On the basis of theoretical calculations the mechanism is expected to be the same for a range of metallic catalysts, with the best ones being Pt and Au, in order. Here, the SO2 electro-oxidation on Pt and Au electrodes was investigated by in situ infrared reflection–absorption (IRRA) spectroelectrochemistry, aiming to elucidate the mechanism. On Pt, species such as dithionate, S2O6 2–, not commonly cited in the literature, were found as intermediates, and PtOH and PtO were suggested as oxidative species. On Au electrodes, the situation observed was completely different. The electrolyte chaotropicity strongly influenced the adsorption of SO2 on Au, changing from Au–O for highly kosmotropic media to Au–S for more chaotropic systems. When the Au–S bond is formed, dithionate and S2O5 2– species were simultaneously present along with the Au­(SO3) complex in solution. The observation of these two species was accompanied by potential oscillations, and an HN-NDR (hidden N-shaped negative differential resistor) oscillator was observed. Different mechanisms for different electrolytes are proposed for Au electrodes.

State of the art electrocatalysts for the hydrogen evolution reaction (HER) are based on metal nanoparticles (NPs). It has been shown that the localized surface plasmon resonance (LSPR) excitation in plasmonic NPs can be harvested to accelerate a variety of molecular transformations. This enables the utilization of visible light as an energy input to enhance HER performances. However, most metals that are active toward the HER do not support LSPR excitation in the visible or near-IR ranges. We describe herein the synthesis of gold−rhodium core− shell nanoflowers (Au@Rh NFs) that are composed of a core made up of spherical Au NPs and shells containing Rh branches. The Au@Rh NFs were employed as a model system to probe how the LSPR excitation from Au NPs can lead to an enhancement in the HER performance for Rh. Our data demonstrate that the LSPR excitation at 533 nm (and 405 nm) leads to an improvement in the HER performance of Rh, which depends on the morphological features of the Au@Rh NFs, offering opportunities for optimization of the catalytic performance. Control experiments indicate that this improvement originates from the stronger interaction of Au@Rh NFs with H 2 O molecules at the surface, leading to an icelike configuration, which facilitated the HER under LSPR excitation.

Electroactive biomaterials that are easily processed as scaffolds with good biocompatibility for tissue regeneration are difficult to design. Herein, the synthesis and characterization of a variety of novel electroactive, biodegradable biomaterials based on poly(3,4-ethylenedioxythiphene) copolymerized with poly(d,l lactic acid) (PEDOT-co-PDLLA) are presented. These copolymers were obtained using (2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanol (EDOT-OH) as an initiator in a lactide ring-opening polymerization reaction, resulting in EDOT–PDLLA macromonomer. Conducting PEDOT-co-PDLLA copolymers (in three different proportions) were achieved by chemical copolymerization with 3,4-ethylenedioxythiophene (EDOT) monomers and persulfate oxidant. The PEDOT-co-PDLLA copolymers were structurally characterized by 1H NMR and Fourier transform infrared spectroscopy. Cyclic voltammetry confirmed the electroactive character of the materials, and conductivity measurements were performed via electrochemical impedance spectroscopy. In vitro biodegradability was evaluated using proteinase K over 35 days, showing 29–46% (w/w) biodegradation. Noncytotoxicity was assessed by adhesion, migration, and proliferation assays using embryonic stem cells (E14.tg2a); excellent neuronal differentiation was observed. These novel electroactive and biodegradable PEDOT-co-PDLLA copolymers present surface chemistry and charge density properties that make them potentially useful as scaffold materials in different fields of applications, especially for neuronal tissue engineering.

SO2 oxidation has been proposed as an alternative pathway for the electrochemical generation of H2 as it requires lower potentials than water splitting and at the same time consumes an atmospheric pollutant. Theoretical predictions suggest that gold and platinum are the most active catalysts for this reaction. This work presents experimental evidence that, contrary to the predictions, SO2 oxidation starts at less positive potentials on Au electrodes (ca. 0.60 V (vs. RHE)) than on Pt. It is found further that the observed current densities on Au are one order of magnitude higher than on Pt. In addition, the SO2 oxidation mechanism depends on the chemical nature of the electrolyte used: a kosmotropic anion (HSO4-) results in lower currents than a chaotropic one (ClO4-) and the latter displays oscillatory reaction rates under both potentiostatic and galvanostatic regimes.