The Use of Density Functional Theory to Decipher the Electrochemical Activity of Metal Clathrochelates with Regard to the Hydrogen Evolution Reaction in the Homogeneous Phase

Abstract

The energetic needs of a rising human population have led to the search for alternative energy sources. A promising route for the large-scale storage of renewable energy is water electrolysis, which is performed with a proton-conducting polymer electrolyte. However, only platinum group metal electrocatalysts have the adequate properties to minimize the overvoltages associated with either hydrogen or oxygen evolution reactions. Alternative materials based on transition metals are scarce, but molecular electrochemistry offers some alternatives. In particular, transition metal clathrochelates exhibit an interesting activity with regard to the hydrogen evolution reaction (HER). However, such complexes form a vast family, and there is a need to implement screening approaches to identify the most performing ones. Theoretical studies on molecular electrocatalysts are adequate for this purpose, since density functional theory (DFT) has a strong predicting capability to provide clues for the improvement of practical devices. This chapter describes the most recent theoretical methods applied to several members of the clathrochelate family. We describe the computation of their common spectroscopic and electrochemical properties. In addition, DFT analysis is used to decipher the multistep reaction mechanism of a model Co clathrochelate with regard to the hydrogen evolution reaction in the homogeneous phase.

Precise Fingerprint Determination of Vibrational Infrared Spectra in a Series of Co(II) Clathrochelates through Experimental and Theoretical Analyses

“…For example, beyond the HER, the use of clathrochelates as dyes for photovoltaic devices has not been performed yet, and in such a context, the prediction of their UV–vis spectra is essential. We have shown, for example, that for TDDFT, the use of the B3LYP/LANL2DZ geometries, but a combination of aug-cc-pVTZ for Co and cc-pVDZ for the rest of the molecule, permits an adequate prediction of electronic spectra . On the other hand, the use of XRD data (whose geometry has been shown here and previously to be accurately predicted via the B3LYP/LANL2DZ combination) with a large set of functionals (OLYP, RPBE, B3LYP, TPSS, BP86) and the Ahlrich’s TZV basis was excellent in predicting electron densities at Fe nuclei and therefore trends in the 57 Fe Mossbauer spectra …”

“…34−36 In particular, Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy methods allow us to study in detail the aforementioned clathrochelate monolayers, immobilized on a surface of various inorganic and organic supports (substrates), thus giving the innovative hybrid organo-inorganic materials. 12,17 Although multiple DFT studies have been performed to address the geometry and electronic structure of clathroche-lates, 25,[30][31][32]37,38 a comprehensive and systematic theoretical description of their vibrational signature (characteristic normal modes and relative intensities of the bands), combined with a thorough comparison to their IR patterns has not been reported been to date. This work has therefore an importance that goes beyond the mere description of IR spectra because the prediction of redox potentials needs the calculation of thermodynamic functions, which are available only after the calculation of the Hessian matrix.…”

“…According to a previous report, a cobalt clathrochelate with the most electron-withdrawing ribbed substituents is found to have the lowest overpotential for the hydrogen-producing process via the 2H + /H 2 pathway. In this context, the use of combined theoretical density functional theory (DFT), spectral electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) studies has proven useful − to assess the electronic structure of various cobalt clathrochelates.…”

“…Although multiple DFT studies have been performed to address the geometry and electronic structure of clathrochelates, ,− ,, a comprehensive and systematic theoretical description of their vibrational signature (characteristic normal modes and relative intensities of the bands), combined with a thorough comparison to their IR patterns has not been reported been to date. This work has therefore an importance that goes beyond the mere description of IR spectra because the prediction of redox potentials needs the calculation of thermodynamic functions, which are available only after the calculation of the Hessian matrix.…”