The influence of CO2 in the oxidant gas on the cell performance of anion-exchange membrane fuel cells was investigated using a three-electrode single cell with a reversible hydrogen electrode (RHE). The overpotential of the cathode was hardly changed by the presence of CO2, while the overpotential of the anode increased after the introduction of CO2 at the cathode. The high anode overpotential was caused by a high CO32- concentration in the anode catalyst layer, even when most of the CO32- ions in the electrolyte membrane are purged during operation through the self-purging mechanism.
Herein, a photocatalytic Giese‐type reaction with alkylsilicates bearing C,O‐bidentate ligands as stable alkyl radical precursors has been reported. The alkylsilicates were prepared in one step from organometallic reagents. Not only primary, secondary, and tertiary alkyl radicals, but also elusive methyl radicals, could be generated by using the present reaction system. The generated radicals were trapped by electron‐deficient olefins bearing various functional groups to give the desired alkyl adducts. The silicon byproduct can be recovered after the photoreaction. The radical generation process was investigated by theoretical calculations, which provided an insight into the facile generation of methyl radicals from methylsilicate bearing C,O‐bidentate ligands.
Suzuki coupling reactions are performed using PdO loaded on dealuminated Y (USY) zeolite. The reaction between bromobenzene and phenylboronic acid is complete in 15 min at room temperature in air, with a turnover number of 1300. The reaction can be repeated at least five times by using 1 wt % Pd. Inductively coupled plasma analysis does not reveal the dissolution of Pd from products, even if the reaction is repeated up to four times. Pd K-edge extended X-ray absorption fine structure analysis reveals the presence of molecular-like PdO and a mixture of Pd(0) -PdO before and after the reaction, respectively. This is probably because Pd stabilized by Al sites is present at the II sites of the Y-type zeolite, as estimated using first-principles calculations. Conversely, Pd species change to PdO clusters after repeated reactions in air using the thermally treated sample.
A photocatalytic Giese‐type reaction using alkylsilicates bearing C,O‐bidentate ligands as stable alkyl radical precursors has been reported. Not only primary, secondary, and tertiary alkyl radicals but also elusive methyl radicals could be generated using the present reaction system. The generated radicals were trapped by electron‐deficient olefins bearing various functional groups to give the desired alkyl adducts. Theoretical calculations provide an insight on the facile generation of methyl radicals from methylsilicate bearing C,O‐bidentate ligands. More information can be found in the Full Paper by T. Morofuji, N. Kano et al. on page 6713.
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