Electrochemistry in supercritical fluids: A mini review

Abstract

A brief overview of the literature relating to electrochemical studies and processes undertaken in supercritical fluids is presented. This review mostly concerns carbon dioxide and hydrofluorocarbons, given the accessibility of their supercritical states, and does not consider the emerging body of research in expanded phase electrochemistry.

Intensified Electrocatalytic CO2 Conversion in Pressure‐Tunable CO2‐Expanded Electrolytes

“…These include the development of structurally complex gas-diffusion electrodes for use in flow cells, [26,27] polymer electrolytes, [28,29] and ionicl iquids [30] that leverage tailorede lectrode-contacting phases to favor high CO 2 availability.I ns ome cases, these approaches rely on interfacial phenomena [31] or involve preparation of membraneelectrode assemblies. [34][35][36][37] Furthermore, the high operating pressures neededt oa chieve supercritical conditions (> 7.38 MPa) pose practical challenges and increase costs. [32,33] However, scCO 2 is ap oor conductor and, even upon pairing with co-solvents, the solubility of most supporting electrolytes MultimolarC O 2 concentrations are achieved in acetonitrile solutions containing supporting electrolyte at relatively mild CO 2 pressures (< 5MPa) and ambient temperature.…”

“…is too low ( 35 mm)tofacilitate high current densitiesand faradaic efficiencies. [34][35][36][37] Furthermore, the high operating pressures neededt oa chieve supercritical conditions (> 7.38 MPa) pose practical challenges and increase costs. Development of new reaction media could help in overcoming these challenges by enabling (1) higher CO 2 concentrations at more modest pressures, (2) sufficient conductivityt oe ngender rapid electron transfer,a nd (3) higherm ass-transfer rates of CO 2 to the electrode surface.…”

The voltammetry of decamethylferrocene and coboltacene in supercritical difluoromethane (R32)

“…As can be seen from Figure Figures 7a and b we can obtain a value for the diffusion coefficient of DMFc using equation (1). These values are given in Table 2.…”

“…However because of the difficulties of working at elevated pressures they have not been that widely studied or used in electrochemistry [1,2]. Recent studies have shown that supercritical fluids are of interest for electrodeposition [3][4][5][6][7], electrosynthesis [8][9][10], and as media for the electrochemical reduction of carbon dioxide [11][12][13].…”

Discrimination of methanol desorption resistance relative to the reaction steps in presence of supercritical n-hexane

“…The reason is that the membrane reactor combines catalytic reactions with separation properties of zeolite membranes. Supercritical fluid (SCF) is obtained when a compound surpasses its critical temperature (T C ) and pressure (P C ) [16]. At this point the fluid displays intermediate properties between a gas and a liquid, producing a unique medium with many of the advantages of both states of matter [17][18][19].…”