Study of the electrochemical reduction of CO_2 on electrodeposited rhenium electrodes in methanol media

摘要

The electrochemical reduction of carbon dioxide at a rhenium electrode electrodeposited onto a polycrystalline gold support was studied by means of polariation curves with simultaneous measurement of mass changes by an electrocemical quartz microbalance (ECQM).Potentiostatic electrolysis was done and the analyses of the reduction products were carried out by gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy.The electrolyte was a methanol solution containing 0.1 M LiClO_4+CO_2,under atmospheric pressure.From the polarization curves it was observed that the CO_2 molecule to form the radical anion,is the rate-controlling step.On the other hand,mass change measurements allow us to determine that CO_2H and CO correspond to the intermediate species formed during CO_2 reduction.The product analysis indicated that the faradaic efficiency for this process depended strongly on the potential at which the electrolysis is carried out and on the hydrodynamic conditions of the solution.Under stirred conditions,the main products were CO(87%) and H_2(13%) at -1.35 V.At thsi same potential and under quiescent conditions,the major products were CO(57%),CH_4(10%) and H_2(33%).