Fast Oxygen Ion Migration in Cu–In–oxide Bulk and Its Utilization for Effective CO2 Conversion at Lower Temperature

Efficient activation of CO2 at low temperature was achieved by reverse water–gas shift via chemical looping (RWGS‑CL) by virtue of fast oxygen ion migration in Cu–In–structured oxide, even at lower temperatures. Results show that novel Cu–In2O3 structured oxide can show a remarkably higher CO2 splitting rate than ever reported. Various analyses revealed that RWGS‑CL on Cu–In2O3 is derived from redox between Cu–In2O3 and CuxIny alloy. Key factors for high CO2 splitting were fast migration of oxide ions in alloy and the preferential oxidation of the interface of alloy–In2O3 in the bulk of the particles. The findings reported herein can open up new avenues to achieve effective CO2 conversion at lower temperatures

Support effects on catalysis of low temperature methane steam reforming

Low temperature ( Nb2O5 > Ta2O5. Surface proton conductivity has a key role for the activation of methane in an electric field. Proton hopping ability on the oxide surface was estimated using electrochemical impedance measurements. Proton transport ability on the oxide surface at 473 K was in the order of CeO2 > Nb2O5 > Ta2O5. The OH group amounts on the oxide surface were evaluated by measuring pyridine adsorption with and without H2O pretreatment. Results indicate that the surface OH group concentrations on the oxide surface were in the order of CeO2 > Nb2O5 > Ta2O5. These results demonstrate that the surface concentrations of OH groups are related to the proton hopping ability on the oxide surface. The concentrations reflect the catalytic activity of low-temperature methane steam reforming in the electric field

Effects of metal cation doping in CeO2 support on catalytic methane steam reforming at low temperature in an electric field

Catalytic methane steam reforming was conducted at low temperature using a Pd catalyst supported on Ce1−xMxO2 (x = 0 or 0.1, M = Ca, Ba, La, Y or Al) oxides with or without an electric field (EF). The effects of the catalyst support on catalytic activity and surface proton hopping were investigated. Results show that Pd/Al-CeO2 (Pd/Ce0.9Al0.1O2) showed higher activity than Pd/CeO2 with EF, although their activity was identical without EF. Thermogravimetry revealed a larger amount of H2O adsorbed onto Pd/Al-CeO2 than onto Pd/CeO2, so Al doping to CeO2 contributes to greater H2O adsorption. Furthermore, electrochemical conduction measurements of Pd/Al-CeO2 revealed a larger contribution of surface proton hopping than that for Pd/CeO2. This promotes the surface proton conductivity and catalytic activity during EF application