Developing Unique Bioelectrochemical Tools to Uncover New Mechanistic Insights of Energy Conversion Processes

Abstract

A self-sustainable society requires optimal renewable energy conversion and storage strategies. Fuel cell is an electrochemical device that convert chemical energy from fuels to electrical energy to power devices. The oxygen reduction reaction (ORR) that occurs at the cathode limits the overall performance of a polymer electrolyte membrane fuel cell due to the inertness of O2. Typically, state-of-the-art Pt or Pt-alloys are employed to overcome the sluggish ORR kinetics. The high cost associated with Pt prevented the widespread adoption of fuel cell technology at present. Low-cost non-precious metal (NPM) catalysts are thus sought to replace Pt. These NPM materials, however, suffer from another limitation, which is the inability to generate H2O selectively as the only product. Selectivity is important because if H2O2 is instead generated as a major side-product, fuel cell components such as the membrane will be damaged by H2O2 and result in catastrophic failure. Some NPM catalysts can rival the performance of Pt, but in general, the activity and selectivity of NPM materials still need to be improved. In this presentation, we describe our efforts in developing a hybrid bilayer membrane (HBM, Fig. 1) nanoplatform to improve the activity and selectivity of an NPM ORR catalyst and unravel unique insights that will lead to high-performing and durable fuel cells [1]. This brand-new electrochemical platform allows for the key thermodynamic and kinetic parameters of proton and electron transfer steps to be modulated independently and systematically, thereby enabling detailed mechanistic studies into the factors that determine the activity and selectivity of the NPM ORR catalyst at the molecular level [2]. HBM results show that the ORR mechanism can be altered by regulating the proton and electron transport rates, resulting in the suppression of the 2e– pathway and the complete elimination of H2O2 as a deleterious by-product. Our team is eager to engage in collaborative studies with prominent researchers in related fields, including spectroscopy, theory, biophysics, biomedical engineering, sensors, flexible electronics, and other applications. We hope our HBM will offer opportunities for interdisciplinary discussions that will enable innovations with practical values in future society.