Three-dimensionally(3D) ordered mesoporous carbon sphere arrays(OMCS) are explored to support high loading(60 wt%) Pt nanoparticles as electrocatalysts for the methanol oxidation reaction(MOR).The OMCS has a unique hierarchical nanostructure with ordered large mesopores and macropores that can facilitate high dispersion of the Pt nanoparticles and fast mass transport during the reactions. The prepared Pt/OMCS exhibits uniformly dispersed Pt nanoparticles with an average size of ~ 2.0 nm on the mesoporous walls of the carbon spheres. The Pt/OMCS catalyst shows significantly enhanced specific electrochemically active surface area(ECSA)(73.5 m^2g^(-1)) and electrocatalytic activity(0.69 mA cm^(-2))for the MOR compared with the commercial 60 wt% Pt/C catalyst.
Gas phase mass transfer in falling film microreactors (FFMRs) with the absorption of CO2 into aqueous solutions of NaOH was investigated.The overall gas-phase mass transfer coefficient increases with NaOH concentration,but decreases as the concentration of CO2 increases.There exists an entrance effect,hindering the mass transfer,which is caused by the dead volume for gas-phase flow in the gas chamber in FFMRs.The entrance effect has a larger impact in a shorter FFMR owing to the relatively large dead volume with respect to that of gas chamber.A decrease in the depth of gas chamber facilitates the mass transfer process.Therefore,the gas-phase entrance or geometry of the gas chamber should be designed appropriately to reduce the entrance effect and improve the mass transfer.
