Vibrational sum-frequency generation spectroscopy of electrode surfaces: studying the mechanisms of sustainable fuel generation and utilisation

Abstract

The electrocatalytic oxidation of water coupled to the reduction of carbon dioxide, to make carbon based products, or the reduction of protons to provide hydrogen, offers a sustainable route to generating useful fuels.

Stripping off of the Hydration Shells in the Double Layer Formation: Water Networks Matter

“…Using IR spectroscopy, Yamakata et al (24) investigated modifications in the ion hydration shells on a CO-covered Pt electrode. Local and intramolecular mode probes have been used in Sum Frequency Generation experiments at aqueous interfaces in operando conditions (31) or in SERS/Stark effect spectroscopies (32).…”

Momentum Relaxed, Plasmon-Resonant Vibrational Sum Frequency Generation of Electrochemical Interfaces: Direct Observation of Carbon Dioxide Electroreduction on Gold

“…Due to the low detection limits and inherent surface sensitivity of Vibrational Sum Frequency Generation (VSFG) spectroscopy, it has become a useful tool for the study of electrochemical interfaces. [1][2][3][4][5][6] VSFG is a second order nonlinear process that occurs between two fields of different frequencies, often a fixed visible field and a broadband or tunable infrared field. [7][8][9] As a second order process, VSFG inherently ignores contributions from centrosymmetric media and is therefore interface specific in the dipole approximation.…”

“…This is because most electrodes are opaque to infrared light, and many electrolytes, including water, also strongly absorb a large portion of the mid-infrared spectrum. 2,10,11 To address this challenge, two experimental geometries have previously been employed for VSFG studies of electrochemical systems. However, as discussed below, each of these possess experimental drawbacks, which have limited their wide spread application for spectroelectrochemistry.…”

“…For this reason, when working in this geometry, the electrode is pressed close against an optical element such as a prism with only an ultrathin (< 50 µm) film of electrolyte sandwiched against the electrode surface. [2][3][4]13,14 While this enables transmission of infrared light to the electrode/electrolyte interface, it results in severe mass transport limitations when attempting to probe faradaic processes, which can introduce experimental artifacts resulting from pH gradients and diffusion controlled kinetics.…”

“…The first method employs a front side geometry, shown in Figure 1a, where the visible and infrared beams approach the interface from the electrolyte side. 2,[12][13][14][15] The benefit of this approach is that it enables the use of a bulk electrode that can be well-characterized and sustain a high current density.…”