Abstract:
Electrocatalytic proton reduction to form dihydrogen (H2) is an effective way to store energy in the form of chemical bonds. In this talk, I will discuss the applicability of a main-group-element-based tin porphyrin complex as an effective molecular electrocatalyst for proton reduction. A PEGylated Sn porphyrin complex displayed high activity and high selectivity in acetonitrile. The maximum turnover frequency (TOFmax) for H2 production was obtained as 1,099 s–1. Spectroelectrochemical analysis, in conjunction with quantum chemical calculations, suggest that proton reduction occurs via an Electron-Chemical-Electron-Chemical pathway. This study reveals that the tin porphyrin catalyst serves as a novel platform for investigating molecular electrocatalytic reactions and provides new mechanistic insights into proton reduction. In this talk, I will also discuss a separate study of electrocatalytic per- and polyfluoroalkyl substances (PFASs) mineralization using a copper(I) catalyst. Groundwater reservoirs contaminated with PFAS need purifying remedies. Perfluorooctanoic acid (PFOA) is the most abundant PFAS in drinking water. Although different degradation strategies for PFOA have been explored, none of them disintegrates the PFOA backbone rapidly under mild conditions. I will present a molecular copper electrocatalyst that assists in the degradation of PFOA up to 93% with 99% defluorination rate within 4 h of cathodic controlled-current electrolysis. Free F–, CF3COO–, CF3H, and CF4 were detected as fragmented PFOA products along with the evolution of CO2 using gas chromatography, ion chromatography, and gas chromatography-mass spectrometry techniques, suggesting comprehensive cleavage of C–C bonds in PFOA. To be discussed in this talk is also our recent progress on high-voltage, membrane-free redox flow batteries (RFBs). Large-scale electrical energy storage (EES) systems are vital for the efficient utilization of widely available intermittent renewable energy sources such as solar and wind energy to mitigate the mismatch between the generation and consumption of electrical energy. Rechargeable batteries are the first choice for building advanced EES systems owing to their high efficiency and flexible installation. Among the various battery technologies being explored, RFBs have attracted particular attention as promising EES systems because of their unique feature of the decoupling of energy density and power. Traditional aqueous RFBs have limitations including limited cell voltage due to narrow electrochemical window of water (<1.6 V) and high cost of a membrane separator. We report high-voltage membrane-free RFBs using an all-organic biphasic system to eliminate the use of aqueous media and a membrane separator.