(Invited) Efficient and Selective Electrocatalytic and Photoelectrochemical Conversion of Energy and Chemicals

Abstract

Due to the intermittent nature of most renewable energy sources (such as solar and wind), practical large scale renewable energy utilization demands both efficient energy conversion and large scale energy storage or alternative usage. Earth-abundant but highly active and selective electrocatalysts are needed to enable efficient and sustainable production of fuels and chemicals using electrocatalytic and photoelectrochemical (PEC) energy conversion. We developed earth-abundant electrocatalysts for highly efficient hydrogen evolution reaction (HER) and oxygen evolution (OER). We recently combined computations and experiments to develop metal compounds as selective catalysts for two-electron oxygen reduction reaction (2e- ORR) to produce hydrogen peroxide (H2O2) and the subsequent electro-Fenton process for upgrading biomass molecules. We have integrated these earth-abundant electrocatalysts with efficient semiconductor materials to demonstrate efficient photoelectrochemical hydrogen generation systems. We also developed high performance hybrid solar-charged storage devices that integrate photoelectrochemical solar cells and redox flow batteries (RFBs). In these integrated solar flow batteries (SFBs), solar energy is absorbed by semiconductor electrodes to directly charge up the redox couples without external electric bias. Such charged redox molecules can then be either discharged to generate the electricity when needed or used to produce fuels and chemicals.