Sustainable production of hydrogen by water electrolysis is a promising pathway to cope with the growing demands for renewable energy conversion and storage. The alkaline electrolysis is attracting increasing attention for more facile anodic oxygen evolution reaction (OER) but plagued by poorer kinetics in cathodic hydrogen evolution reaction (HER) even with the platinum (Pt) catalysts. With the presence of alkali metal cations and hydroxyl anions, the electrode-electrolyte (Pt-water) interface in alkaline electrolyte is far more complex than that in acidic environment. Despite considerable efforts in probing the HER kinetics in alkaline electrolyte, the exact role of these different species remains elusive and represents a topic of considerable debate. Herein, we combine electrochemical impedance spectroscopy (EIS) and a unique electrical transport spectroscopy (ETS) approach to probe and understand the fundamental role of different cations (Li + , Na + and K + ) in HER kinetics. The ETS approach provides a highly specific signaling transduction pathway to exclusively probe the surface adsorbates, while the EIS offers the critical information regarding the near surface environment in the electrical double layer (EDL). Based on these comprehensive on-surface and near-surface signals, our theoretical calculations with explicit solvation further help establish the molecular level insights into the surface adsorption properties, solvation structure, and Pt-water interface dynamics in presence of different cations and surface hydroxyl adsorbate (OH ad ). Our integrated studies
The development of future sustainable energy technologies relies critically on our understanding of electrocatalytic reactions occurring at the electrode–electrolyte interfaces, and the identification of key reaction promoters and inhibitors. Here we present a systematic in situ nanoelectronic measurement of anionic surface adsorptions (sulfates, halides, and cyanides) on ultrathin platinum nanowires during active electrochemical processes, probing their competitive adsorption behavior with oxygenated species and correlating them to the electrokinetics of the oxygen reduction reaction (ORR). The competitive anionic adsorption features obtained from our studies provide fundamental insight into the surface poisoning of Pt-catalyzed ORR kinetics by various anionic species. Particularly, the unique nanoelectronic approach enables highly sensitive characterization of anionic adsorption and opens an efficient pathway to address the practical poisoning issue (at trace level contaminations) from a fundamental perspective. Through the identified nanoelectronic indicators, we further demonstrate that rationally designed competitive anionic adsorption may provide improved poisoning resistance, leading to performance (activity and lifetime) enhancement of energy conversion devices.
Electrocatalytic hydrogen evolution reaction (HER) is critical for green hydrogen generation and exhibits distinct pH-dependent kinetics that have been elusive to understand. A molecular-level understanding of the electrochemical interfaces is essential for developing more efficient electrochemical processes. Here we exploit an exclusively surface-specific electrical transport spectroscopy (ETS) approach to probe the Pt-surface water protonation status and experimentally determine the surface hydronium pK a = 4.3. Quantum mechanics (QM) and reactive dynamics using a reactive force field (ReaxFF) molecular dynamics (RMD) calculations confirm the enrichment of hydroniums (H 3 O + * ) near Pt surface and predict a surface hydronium pK a of 2.5 to 4.4, corroborating the experimental results. Importantly, the observed Pt-surface hydronium pK a correlates well with the pH-dependent HER kinetics, with the protonated surface state at lower pH favoring fast Tafel kinetics with a Tafel slope of 30 mV per decade and the deprotonated surface state at higher pH following Volmer-step limited kinetics with a much higher Tafel slope of 120 mV per decade, offering a robust and precise interpretation of the pH-dependent HER kinetics. These insights may help design improved electrocatalysts for renewable energy conversion.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.