| Autor: |
Xu P; Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States., Wang R; Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States.; Center for Complex Materials from First-Principles (CCM), Temple University, Philadelphia, Pennsylvania 19122, United States., Zhang H; Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States., Carnevale V; Institute for Computational Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States.; Department of Biology, Temple University, Philadelphia, Pennsylvania 19122, United States., Borguet E; Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States.; Center for Complex Materials from First-Principles (CCM), Temple University, Philadelphia, Pennsylvania 19122, United States., Suntivich J; Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States.; Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14850, United States. |
| Abstrakt: |
The molecular details of an electrocatalytic interface play an essential role in the production of sustainable fuels and value-added chemicals. Many electrochemical reactions exhibit strong cation-dependent activities, but how cations affect reaction kinetics is still elusive. We report the effect of cations (K + , Li + , and Ba 2+ ) on the interfacial water structure using second-harmonic generation (SHG) and classical molecular dynamics (MD) simulation. The second- (χ H 2 O (2) ) and third-order (χ H 2 O (3) ) optical susceptibilities of water on Pt are smaller in the presence of Ba 2+ compared to those of K + , suggesting that cations can affect the interfacial water orientation. MD simulation reproduces experimental SHG observations and further shows that the competition between cation hydration and interfacial water alignment governs the net water orientation. The impact of cations on interfacial water supports a cation hydration-mediated mechanism for hydrogen electrocatalysis; i.e., the reaction occurs via water dissociation followed by cation-assisted hydroxide/water exchange on Pt. Our study highlights the role of interfacial water in electrocatalysis and how innocent additives (such as cations) can affect the local electrochemical environment. |
