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I n our communication 1 , we have investigated Pt nanoparticles supported on high surface area carbons (Pt/C) and boron carbide composites (Pt/BC). We showed that purely electronic interactions between the nanoparticulate catalyst and its support have bearings on electrocatalytic activity for the oxygen reduction reaction in acidic media and catalyst stability. This has been achieved by interrogating the electronic states of the supported Pt catalysts in an electrochemical environment via X-ray absorption near edge structure (XANES), which showed a relatively more positive charge on Pt nanoparticles if supported on BC compared to very similar Pt nanoparticles supported on C. Similarity of the Pt nanoparticle size distribution and morphology was established by transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS), respectively, to exclude other factors contributing to the electrocatalytic characteristics.We also investigated the two catalysts ex situ under ultra-high vacuum (UHV) conditions by X-ray photoelectron spectroscopy (XPS), which has shown a shift to higher binding energies of the Pt 4f signal relative to the reference C 1s signal for the Pt/BC catalyst. Following the band filling argument put forward by Watanabe et al. 2 , we have tentatively interpreted this change with a relatively more negative charge of Pt supported on BC compared to Pt on C under UHV conditions. A fuller account of the reasoning is contained in the published reviewer file of our original communication.This led us to point out that the relative state of charge of the Pt nanoparticles on the two supports (i.e., more negative or more positive) appears different under potentiostatic control in aqueous electrolyte than under UHV conditions. In an attempt to rationalise this observation, we have argued that the overall work function of the heterogeneous electrode surfaces should be different for the Pt/C and Pt/BC systems, which leads to a shift of the potential of zero charge (pzc) 3 of the heterogeneous Pt/BC electrode surface relative to Pt/C. An additional positive charge has, therefore, to be accommodated by the Pt/BC electrode if held at the same potential, because it is further away from the pzc.Binninger addressed this minor point 4 . In an attempt to show that "no inversion of the relative charge transfer between support and Pt nanoparticle can be deduced", Binninger has put forward an electrostatic argument. He investigates the potential at which the nanoparticle electrolyte-facing, external surface has zero charge in the limit of infinitely strong screening (i.e., where the Debye length is much shorter than the catalyst particle size) in the electrolyte in detail and concludes that this potential is the same as is found for an extended Pt electrode under the same conditions. This result is unsurprising given that the assumption of infinite screening will quench all electrostatic interaction between nanoparticle and support through the electrolyte. Binninger then qualitatively expands his co...
I n our communication 1 , we have investigated Pt nanoparticles supported on high surface area carbons (Pt/C) and boron carbide composites (Pt/BC). We showed that purely electronic interactions between the nanoparticulate catalyst and its support have bearings on electrocatalytic activity for the oxygen reduction reaction in acidic media and catalyst stability. This has been achieved by interrogating the electronic states of the supported Pt catalysts in an electrochemical environment via X-ray absorption near edge structure (XANES), which showed a relatively more positive charge on Pt nanoparticles if supported on BC compared to very similar Pt nanoparticles supported on C. Similarity of the Pt nanoparticle size distribution and morphology was established by transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS), respectively, to exclude other factors contributing to the electrocatalytic characteristics.We also investigated the two catalysts ex situ under ultra-high vacuum (UHV) conditions by X-ray photoelectron spectroscopy (XPS), which has shown a shift to higher binding energies of the Pt 4f signal relative to the reference C 1s signal for the Pt/BC catalyst. Following the band filling argument put forward by Watanabe et al. 2 , we have tentatively interpreted this change with a relatively more negative charge of Pt supported on BC compared to Pt on C under UHV conditions. A fuller account of the reasoning is contained in the published reviewer file of our original communication.This led us to point out that the relative state of charge of the Pt nanoparticles on the two supports (i.e., more negative or more positive) appears different under potentiostatic control in aqueous electrolyte than under UHV conditions. In an attempt to rationalise this observation, we have argued that the overall work function of the heterogeneous electrode surfaces should be different for the Pt/C and Pt/BC systems, which leads to a shift of the potential of zero charge (pzc) 3 of the heterogeneous Pt/BC electrode surface relative to Pt/C. An additional positive charge has, therefore, to be accommodated by the Pt/BC electrode if held at the same potential, because it is further away from the pzc.Binninger addressed this minor point 4 . In an attempt to show that "no inversion of the relative charge transfer between support and Pt nanoparticle can be deduced", Binninger has put forward an electrostatic argument. He investigates the potential at which the nanoparticle electrolyte-facing, external surface has zero charge in the limit of infinitely strong screening (i.e., where the Debye length is much shorter than the catalyst particle size) in the electrolyte in detail and concludes that this potential is the same as is found for an extended Pt electrode under the same conditions. This result is unsurprising given that the assumption of infinite screening will quench all electrostatic interaction between nanoparticle and support through the electrolyte. Binninger then qualitatively expands his co...
Lithium–sulfur (Li–S) batteries have attracted wide attention as high‐energy‐density energy storage devices, but their practical applications are hindered by the severe shuttle effect and sluggish kinetics of lithium polysulfides (LiPSs). To address these challenges, polar mediators are employed to chemisorb and catalyze LiPSs, but most of them suffer from low electronic conductivity and poor catalytic activity. Here, a novel strategy is reported to enhance both properties by dispersing Fe(III) atoms in VO2 nanoribbons(Fe‐VO2), creating electronic metal‐support interactions (EMSI) that modulate the electronic structure and charge transfer of VO2. Theoretical calculations reveal that EMSI lowers the energy barrier for the decomposition of Li2S from 1.60 to 1.32 eV and increases the electronic conductivity of VO2. Fe doping reduces the Li‐ions diffusion barrier from 1.42 eV in VO2 to 0.99 eV in Fe‐VO2. The Fe‐VO2 catalyst shows strong adsorption and fast converstion of LiPSs, resulting in high energy density and long cycling life of Li‐S batteries. The cathode with Fe‐VO2 maintains a higher capacity retention of 67% after 500 cycles at 1 C, compared with 52.4% and 53.6% for the carbon black based cathode and VO2 based cathode, respectively. This work demonstrates the potential of EMSI for designing efficient catalysts for Li–S batteries and provides new insights into the electronic structure engineering of polar mediators.
The electrical double-layer playsakey role in important interfacial electrochemical processes from catalysis to energy storage and corrosion. Therefore,u nderstanding its structure is crucial for the progress of sustainable technologies. We extract new physico-chemical information on the capacitance and structure of the electrical double-layer of platinum and gold nanoparticles at the molecular level, employingsingle nanoparticle electrochemistry.The charge storage ability of the solid/liquid interface is larger by one order-of-magnitude than predicted by the traditional mean-field models of the doublelayer such as the Gouy-Chapman-Stern model. Performing molecular dynamics simulations,w ei nvestigate the possible relationship between the measured high capacitance and adsorption strength of the water adlayer formed at the metal surface.T hese insights may launch the active tuning of solidsolvent and solvent-solvent interactions as an innovative design strategy to transform energy technologies towards superior performance and sustainability.
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