Sains Malaysiana 36(1): 27-32 (2007)

Adsorbed CO at Polycrystalline Copper in Phosphate Buffered Solution

(CO Terjerap dipermukaan Kuprum Polihablur dalam Larutan Tampan Fosfat)

Jumat Salimon

Pusat Pengajian Sains Kimia dan Teknologi Makanan

Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia

43600 UKM Bangi Selangor D.E. Malaysia

AbstraCT

The adsorption of CO at polycrystalline copper surface was investigated spectroscopically.   It  was  found  that  CO adsorbed  as  a linear adsorbed CO, Cu-CO_L and was a dominant species on copper surface at low CO concentration.   A Cu-CO_L was electrochemically converted to a bridge bonded CO, Cu-CO_B at a high CO concentration condition.  Increasing the CO surface coverage, q_CO will increase the formation of adsorbed bridge bonded CO.  A nitrogen gas purging treatment was used to examine the stability of an adsorbed CO through the evacuation process.  The result showed that Cu-CO_B remained intact while Cu-CO_L was completely removed from the copper surface.  It suggests that Cu-CO_L may involve in a weak bonding to a copper surface such as in a physisorbed interaction, while Cu-CO_B consists much stronger bonding such as a chemisorbed interaction.  The N₂ purging treatment also gave an additional prove that Cu-CO_B was partly converted to Cu(I)-CO at anodic potential regions.

Keywords: Adsorbed carbon monoxide; copper surface

AbsTRAK

Penjerapan CO di atas permukaan polihablur kuprum telah dikaji melalui sifat spektroskopiknya.  Didapati CO yang terjerap wujud dalam bentuk CO terjerap linear, Cu-CO_L dan merupakan bentuk CO terjerap yang dominan pada kepekatan CO yang rendah.  Cu-CO_L bertukar secara elektro-kimia ke bentuk CO terjerap secara jambatan, Cu-CO_B pada kepekatan CO yang tinggi.   Penambahan penurapan permukaan CO, q_CO akan menambahkan kadar pembentukan CO terjerap secara jambatan.  Kestabilan CO terjerap telah diuji secara pengolahan penyahjerapan melalui proses alih tukar gas nitrogen.  Hasil kajian menunjukkan bahawa Cu-CO_B didapati masih kekal manakala Cu-CO_L telah terkeluar keseluruhannya dari permukaan kuprum.   Ini mencadangkan bahawa pembentukan Cu-CO_L melibatkan ikatan secara lemah ke atas permukaan kuprum seperti jerapan fizik, sementara Cu-CO_B terlibat dengan ikatan yang kuat seperti jerapan kimia.   Pengolahan alih tukar gas nitrogen juga memberi bukti tambahan bahawa sebahagian Cu-CO_B telah bertukar kebentuk kuprum(I) karbonil, Cu(I)-CO pada julat keupayaan anodik.

Kata kunci: Karbon monoksida terjerap; permukaan kuprum

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