Electrical reduction of perovskite electrodes for accelerating exsolution of nanoparticles

Abstract

Growth of finely dispersed nanocatalysts by exsolution of metal nanoparticles from perovskite oxides under reducing conditions at elevated temperature is a promising approach of producing highly active catalytic materials. An alternative method of exsolution using an applied potential has been recently shown to potentially accelerate the exsolution process of nanoparticles that can be achieved in minutes rather than the hours required in chemical reduction. In the present study, we investigate exsolution of nanoparticles from perovskite oxides of La 0.43 Ca 0.37 Ni 0.06 Ti 0.94 O 3-γ (LCTNi) and La 0.43 Ca 0.37 Ni 0.03 Fe 0.03 Ti 0.94 O 3-γ (LCTNi-Fe) under applied potentials in carbon dioxide atmosphere. The impedance spectra of single cells measured before and after electrochemical poling at varying voltages showed that the onset of exsolution process occurred at 2 V of potential reduction. An average particle size of the exsolved nanoparticles observed after testing using a scanning electron microscopy was about 30-100 nm. The cells with the reduced electrodes exhibited desirable electrochemical performances not only in pure carbon dioxide (current density of 0.37 A cm −2 for LCTNi and 0.48 A cm −2 for LCTNi-Fe at 1.5 V) but also in dry hydrogen (0.36 W cm −2 for LCTNi and 0.43 W cm −2 for LCTNi-Fe).

A Review on Perovskite-Type LaFeO3 Based Electrodes for CO2 Reduction in Solid Oxide Electrolysis Cells: Current Understanding of Structure–Functional Property Relationships

“…It was also shown that the nanoparticle ex-solution in electrochemical cells can be reached by the application of an electrical potential. 120 Specifically, metallic nanoparticles of size 30−100 nm were obtained from La 0.43 Ca 0.37 Ni 0.06 Ti 0.94 O 3 (LCTNi) and La 0.43 Ca 0.37 Ni 0.03 Fe 0.03 Ti 0.94 O 3 (LCTNi-Fe) perovskite phases in a carbon dioxide environment at the reduction potential over 2 V. As can be seen in Figure 14, such cells have shown 121 The XRD results have shown that the chemical composition of the obtained nanoparticles is Fe 0.64 Ni 0.36 . In addition, some La 2 O 3 was formed, which is undesirable due to its low activity.…”

Unraveling the evolution of exsolved Fe–Ni alloy nanoparticles in Ni-doped La0.3Ca0.7Fe0.7Cr0.3O3−δ and their role in enhancing CO2–CO electrocatalysis

“…22 The NPs not only provide active sites for CO 2 /CO adsorption but also increase the catalytically active surface area. 23,24 In situ NP exsolution has been demonstrated in a variety of perovskite systems, such as La 0.52 Sr 0.28 Ni 0.06 Ti 0.94 -O 3 , 21 La 0.43 Ca 0.37 Ni 0.03 Fe 0.03 Ti 0.94 O 3Àg , 25 24 and, Pr 0.5 Ba 0.5 Mn 0.9 Co 0.1 O 3 , 28 to name a few.…”

Trends and Prospects of Bimetallic Exsolution

“…Redox exsolution, an alternative to assembly and deposition methods, has the potential to produce supported metal nanoparticles with combined high activity and stability. In this method, active species are substituted in a perovskite oxide matrix and subsequently emerge as metal nanoparticles at the surface, normally driven by thermal [3] or electrical reduction [4] . Exsolved nanoparticles are epitaxially grown from the parent oxide and partially socketed in it.…”