Sains Malaysiana 31: 73-85 (2002)                                                                                Sains Fizis dan Gunaan /

                                                                                                                                Physical and Applied Sciences

Surface Pretreatment  Effect on the Electrochemical Reduction

of CO₂ on Polycrystalline Copper III Aqueous

Hydrogen Carbonate Solution

Jumat Salimon

School of Chemical Sciences & Food Technology

Universiti Kebangsaan Malayisa

43600 UKM Bangi, Selangor D.E.,Malaysia

Maher Kalaji

Department of Chemistry

University of Wales

Bangor UK LL57 2UW

ABSTRACT

A major obstacle that arises during the electroreduction of carbon dioxide in aqueous solution is the formation of inactive specie on the surface of electrode. The route that leads the formation of carbonate ions during the reduction of CO₂ is minimized through surface electro-polarization of the electrode. As the polarization potential is varied from -1.0 to 1.5 V (vs. SCE), an adsorbed carbon monoxide band that shifts from 1889 to 1920 cm^-1 appeared, indicating that an adsorbed carbon monoxide is produced from the reduction of CO₂, The band was not observed without surface pre­polarization or in nitrogen-saturated solution. These results confirm that the "carbonate route" can be overcame and depressed during the electroreduction of CO₂ in aqueous solution. Studies performed using other electrodes (Ni and Pt) show the same behaviour although in different potential ranges. Com­parison with similar studies reported in recent literature suggests that the history of the electrode and pre-treatment are very critical.

ABSTRAK

Salah satu sebab penghalang semasa proses penurunan karbon dioksida dalam larutan akuas adalah pembentukan species tak aktif pada permukaan elektrod. Tapak jalan penghasilan ion tak aktif carbonat, boleh diminimakan melalui pempolaran permukaan elektrod secara elektrokimia. Apabila keupayaan pempolaran diubahkan dari -1.0 ke-1.5 V (vs. SCE), satu puncak inframerah bagi carbon monoksida terjerap yang teranjak dari 1889 ke 1920 cm^-1 terhasil, menunjukkan bahawa CO₂ telah mengalami proses penurunan. Puncak ini tidak dapat dicerap jika permukaan elektrod tidak dipolarkan terlebih dulu atau dalam larutan yang tidak ditepukan dengan karbon dioksida. Kajian yang dilakukan terhadap elektrod berlainan (Ni dan Pt) juga menunjukkan kehadiran puncak yang sama walaupun dalam julat keupayaan yang berbeza. Perbandingan dengan kajian penurunan karbon dioksida yang telah dilaporkan dalam literatur terkini merumuskan bahawa keadaan latarbelakang dan pra-olahan permukaan elektrod merupakan faktor yang amat kritikal dan perlu diambil kira.  

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