Periodic Reporting for period 1 - VSHER (Mechanistic Understanding of Heterogenised Hydrogen Evolution Catalysts Through Vibrational Spectroelectrochemistry)
Reporting period: 2016-04-01 to 2018-03-31
In this project, we develop innovative spectroscopic approaches that allow for in situ investigations of the mechanism of molecular CO2 reduction catalysis. Specifically, powerful Fourier-transform infrared spectroscopy in the attenuated reflection mode coupled to electrochemistry is employed to investigate the interfacial catalytic reactions of manganese and rhenium transition metal complexes at a molecular level. Upon developing tailored immobilization strategies, we selectively bind the catalysts onto conductive electrode surfaces that enable controlled triggering of redox and catalytic reactions by applying potentials. Our studies aim at providing a detailed picture of the catalytic mechanism of these complexes on surfaces deriving general guidelines for rational enhancement of activity and selectivity for CO2 reduction catalysis.
Chemical synthesis was used to achieve highly catalytically active transition metal complexes bearing manganese and rhenium metal centers as active sites, respectively, as well as anchors at the ligand frame to allow for quantitative immobilization of the catalysts on highly conductive carbon nanotube film electrodes leading to improved activities that outcompete many molecular catalysts currently employed.
Investigations of the heterogenised molecular catalytic systems by means of the developed infrared spectroscopic approach led to a detailed understanding of redox induced reactions of the compounds. Infrared detection of redox intermediate species formed upon reduction of the immobilized catalysts enabled rationalization of activity and, importantly, selectivity of the compounds explaining the observed product distribution in electrocatalysis experiments conducted in parallel.
The developed infrared spectroscopic approach that enabled the detection of these species bears potential to investigate a range of interfacial reactions beyond molecular CO2 reduction catalysis. Its high sensitivity and the coupling to electrochemical control make this method also extremely powerful to study heterogeneous catalytic reactions such as CO2 reduction promoted by bulk surfaces as well as enzymatic transformations at conductive interfaces relevant for bioelectronical devices.