Infrared spectroscopic study of the carbon dioxide adsorption on the surface of Ga2O3 polymorphs
Infrared spectroscopic study of the carbon dioxide adsorption on the surface of Ga2O3 polymorphs
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DOI：
10.1021/jp055594c
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发表时间：
2006-03-23
影响因子：
3.3
通讯作者：
Bonivardi, AL
中科院分区：
文献类型：
--
作者：
Collins, SE;Baltanás, MA;Bonivardi, AL
用原位红外光谱研究了具有不同晶相(α、β和伽马)和比表面积(12-105m(2)g(-1))的氧化镓(III)晶型对CO2的吸附。在活化的GaAs(即在723K的O-2和D-2(H-2)下部分脱羟基)的裸表面上，O-D(O-H)伸缩模式的几个IR信号被分配给以四面体和/或八面体位置与镓离子键合的单配位、双配位和三配位的OD(OH)基团。在323K下，多晶型的表面暴露在CO2中，出现了各种(双)碳酸盐物种。碱性较强的羟基能与二氧化碳反应生成两种碳酸氢盐：单(m-)和双齿(b-)[v(As)，(CO3)=1630 cm(-1)；v(S)(CO3)=1431或1455 cm(-1)(m-或b-)；6(OH)=1225 cm(-1)]。与重碳酸盐基团一起，红外光谱谱带归属为：羧酸盐[v(As)(CO_2)=1750 cm(-1)；v(S)(CO_2)=1170 cm(-1)]，桥式碳酸盐[v(As)(CO_3)=1680 cm(-1)；v(As)(CO_3)=1280 cm(-1)]，双齿碳酸盐[Va，(CO_3)=1587 cm~(-1)；v，(CO_3)=第1325 cm(-1)]，多齿碳酸盐[x(As)(CO_3)=1460 cm(-1)]；V(S)(CO_3)=1406厘米(-1)]物种发育，二氧化碳排放量高达约600Torr。然而，在323K放气后，只有双齿和多齿碳酸盐基团仍然留在样品的表面。体积吸附(323K)测得的总吸附CO2量类似于2.0mmolm(-2)在任何晶型上，与(双)碳酸盐物种的积分吸光度与材料的表面积成正比。在流动的CO2(760Torr)下加热时，大多数(双)碳酸盐物种消失了T&gT；550K，但多齿基团仍保留在表面，直到使用的最高温度(723K)。对二氧化碳吸附过程中更可能的表面位置进行了深入的讨论。
The adsorption Of CO2 over a set of gallium (III) oxide polymorphs with different crystallographic phases (alpha, beta, and gamma) and surface areas (12-105 m(2) g(-1)) was studied by in situ infrared spectroscopy. On the bare surface of the activated gallias (i.e., partially dehydroxylated under O-2 and D-2 (H-2) at 723 K), several IR signals of the O-D (O-H) stretching mode were assigned to mono-, di- and tricoordinated OD (OH) groups bonded to gallium cations in tetrahedral and/or octahedral positions. After exposing the surface of the polymorphs to CO2 at 323 K, a variety of (bi)carbonate species emerged. The more basic hydroxyl groups were able to react with CO2, to yield two types of bicarbonate species: mono- (m-) and bidentate (b-) [v(as),(CO3) = 1630 cm(-1); v(s)(CO3) = 1431 or 1455 cm(-1) (for m- or b-); 6(OH) = 1225 cm(-1)]. Together with the bicarbonate groups, IR bands assigned to carboxylate [v(as)(CO2) = 1750 cm(-1); v(s)(CO2) = 1170 cm(-1)], bridge carbonate [v(as)(CO3) = 1680 cm(-1); v(as)(CO3) = 1280 cm(-1)], bidentate carbonate [Va,(CO3) = 1587 cm-1; v,(CO3) = 1325 cm(-1)], and polydentate carbonate [x(as)(CO3) = 1460 cm(-1); v(s)(CO3) = 1406 cm(-1)] species developed, up to approximately 600 Torr Of CO2. However, only the bi- and polydentate carbonate groups still remained on the surface upon outgassing the samples at 323 K. The total amount of adsorbed CO2, measured by volumetric adsorption (323 K), was similar to 2.0 mu mol m(-2) over any of the polymorphs, congruent with an integrated absorbance of (bi)carbonate species proportional to the surface area of the materials. Upon heating under flowing, CO2 (760 Torr), most of the (bi)carbonate species vanished a T > 550 K, but polydentate groups remained on the surface up to the highest temperature used (723 K). A thorough discussion of the more probable surface sites involved in the adsorption of CO2 is made.