Electrochemistry: Development of a Macro SI-SECM Protocol to Investigate Reaction Intermediates for the HER and OER, and its Use for Designing Earth- Abundant Electrocatalysts
Abstract
This research proposal has four objectives in order to experimentally verify the predicted role of surface intermediate bonding strength in electrocatalytic activity, and determine whether this knowledge can be used to predict and screen for new earth-abundant electrocatalysts. The first objective of this proposal sets out to overcome the ultramicroelectrode (UME) substrate limitation of Surface-Interrogation Scanning Electrochemical Microscopy (SI-SECM) in order to allow for SI-SECM to be performed on any catalytic material. One of the drawbacks of SI-SECM is that the substrate must be small relative to the tip electrode to prevent open circuit positive feedback on conductive substrates. We intend to overcome this limitation by developing a unique masking technique and a computer-controlled auto-alignment method which could be used for both SECM and SI-SECM. This auto-alignment procedure will drastically advance the state-of-the-art for SECM and it will be useful for other forms of SECM such as substrate-generation/tip-collection SECM. In addition to performing surface interrogation on any material as described above, using this procedure with small electrodes would provide very close tip/substrate distances which will advance the study of heterogeneous electron transfer kinetics. Furthermore, using the exact same procedure with large tip electrodes would allow us to achieve near 100% collection efficiency in the substrate generation/tip collection mode of SECM which would enhance the ability to measure heterogeneous electron transfer kinetics on a wide variety of substrates. While other electrochemical techniques exist (e.g. EC-STM, EC-AFM, AFM-SECM), this modified SI-SECM would be the only technique that could do surface interrogation and have an in-situ method of measuring products of any electrocatalytic surface with a near 100% collection efficiency. The second objective of this proposal will investigate the surface coverage of adsorbed intermediates and the homogeneous kinetics of the intermediate reacting with a titrant on selected elements and single element oxides to determine if these properties can be used as predictors for catalytic activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). This will be done using the SI-SECM technique developed in Objective 1. It is hypothesized that the surface coverage and/or the homogeneous kinetics as determined by SISECM are related to the bond strength of the surface intermediate, and thus can be used as a predictor of catalytic activity. In this objective, we will correlate these surface intermediate measurements to the electrochemical activities of the HER and OER. We anticipate that these correlations will follow the theoretically-predicted volcano relationships. Measuring these quantities in solution via SECM will provide valuable insights into the mechanisms of these reactions and will guide the development of new earth-abundant electrocatalysts. The third objective...
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 06, 2018
- Source ID
- W911NF1710098
Entities
People
- Kevin C Leonard
Organizations
- Army Contracting Command
- United States Army
- University of Kansas