Author: Haibin NingPublisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0
Book Description
The defects-rich cerium oxide (CeO2) supported metal oxide or metal catalysts (Cu, Co, Ni, Fe, Mn and Ru) for catalytic CO2 reduction were studied. For comparison, thermal catalysis, plasma catalysis and electrocatalysis techniques were carried out under various equilibrium and non-equilibrium experimental conditions. The effects of particle morphology, surface modification and reduction treatment on CeO2 supports and supported catalysts were also investigated and discussed to understand the underlying mechanisms in terms of the valence states, surface defects and support-catalyst interaction.A series of surface engineered CeO2 (nanorods, nanocubes, and nanoctahedra) supported metal oxide catalysts were synthesized, characterized and applied to achieve low-temperature and energy-efficient CO2 reduction. The comparison between thermal catalysis under thermodynamic equilibrium conditions and plasma catalysis under non-equilibrium conditions reveals the promotion effect of plasma on the catalytic activity of CO2 hydrogenation with the ionized gas in the plasma region via the formation of highly reactive species (i.e., vibrationally and electronically excited ions and free radicals). The effect of reduction activation treatment was examined that could change the valence states of Ru species and provide alternative reaction pathways for CO2hydrogenation, leading to higher CO2 conversion at low temperature (~95% at 150 oC) under plasma conditions. Furthermore, ~89 % CO2 conversion and ~98 % CH4 selectivity were obtained for surface modified CeO2 nanorods (mCeO2NR) supported RuOx catalysts at 150 oC, companied with excellent stability (~87 % CO2 conversion at 350 oC). Applying surface modification on the CeO2 surface generates more surface defects (oxygen vacancy, voids, and steps, etc.) as anchoring sites for Ru species and increases the thermal stability of catalyst clusters.Additionally, electrocatalytic conversion of CO2 was conducted at room temperature under atmospheric pressure with CeO2 doped RuOx catalyst films. Different CeO2 nanocrystals including pristine CeO2NR, mCeO2NR, CeO2 nanocubes (CeO2NC) and CeO2 nanoctahedra (CeO2NO) were doped into RuOx and the mCeO2NR-RuOx thin film was found to present the highest current density (166 mA/cm2 at -1.6 V vs RHE.) with the highest double-layer capacitance (100 mF/cm2) and lowest resistance from the linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry results.
