Investigation of Highly Effective and Stable Electrocatalysts for Electrochemical CO2 Reduction at Room and Elevated Temperatures

• Author / Creator

  Liu,Subiao

• To effectively reduce and utilize atmospheric CO2, electrochemically converting it to CO on an efficient and stable electrocatalyst at room and elevated temperatures has attracted extensive interests. However, present electrocatalysts usually suffer from sluggish kinetics, high overpotential, low selectivity and energy efficiency. Therefore, it is highly desirable to search for novel catalysts that can efficiently facilitate the CO2RR at room and elevated temperatures. I demonstrated a predominant shape-dependent electrocatalytic reduction of CO2 to CO on triangular silver nanoplates (Tri-Ag-NPs) in 0.1 M KHCO3 at room temperature. Compared with similarly sized Ag nanoparticles and bulk Ag, Tri-Ag-NPs exhibited an enhanced current density and significantly improved Faradaic efficiency and energy efficiency with a considerable durability. To further study the effects of electrocatalyst structure and employed solvent, I successfully prepared Ag2S nanowires (NWs) using a facile one-step method and utilized it as an electrocatalyst for CO2RR. Ag2S NWs in ionic liquid (IL) possess a partial current density of 12.37 mA cm-2, about 14 and 17.5-fold higher than those of Ag2S NWs in KHCO3 and bulk Ag. Moreover, it shows significantly higher selectivity with a value of 92.0% at η of -0.754 V. More importantly, the CO formation begins at an ultralow η of 54 mV. These studies demonstrate shape and structure influences of electrocatalysts as well as employed solvent in tuning electrocatalytic activity and selectivity of metal/non-mental catalysts for CO2RR. I also developed a new Ni-doped La(Sr)FeO3-δ as an electrocatalyst for CO2RR at elevated temperatures. To further increase the electrochemical performance of La(Sr)Fe(Ni), the powders were reduced in a tubular furnace in a reducing gas flow, thus forming in situ exsolved Fe-Ni alloy nanospheres on the backbone of LSFN since the catalysts coated with functional metal/alloy nanoparticles can significantly improve the catalytic activity and coking resistance in hydrocarbon fuels. Additionally, I developed an electrocatalyst with in situ exsolved Co-Fe alloy nanoparticles embedded in an active (Pr0.4Sr0.6)3(Fe0.85Mo0.15)2O7 double-layered perovskite backbone, which also acts as a more stable and efficient electrocatalyst to promote CO2RR compared to the Pr0.4Sr0.6Co0.2Fe0.7Mo0.1O3-δ cubic perovskite. Therefore, these newly developed perovskites point to a new direction to develop highly efficient catalysts in the form of the perovskite oxides with uniformly in situ exsolved metal/bimetal nanospheres/nanoparticles.

• Subjects / Keywords

  • Electrocatalyst
  • Electrocatalysis
  • CO2 reduction
  • Perovskite

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3ZK56126

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.