科研之友
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摘要
The use of graphene oxide (GO) as support has been shown previously to improve the CO, adsorption performance of layered double oxides (LDOs). In this contribution, the separate promoting effect of GO has been distinguished clearly from the influence of alkali species remaining from the layered double hydroxide coprecipitation. A range of sodium-free LDO and LDO/GO hybrids with relatively low GO loadings have been prepared and characterized. These have been compared to adsorbents with sodium residues deliberately left by minimum washing of the precipitates. The incorporation of GO was found to enhance considerably the thermal stability of the LDO and to reduce the loss of site heterogeneity during temperature swing cycling. The impact of the gradual loss of surface heterogeneity of the materials on the CO2 adsorption equilibrium is shown to be described by the Toth model. CO2-TPDs did not reveal any significant modification in the nature of the sites relevant for adsorption at 573 K induced by the presence of GO in the range of loadings studied. Sodium ions incorporated by leaving residual sodium from the synthesis greatly enhanced the adsorption capacity of the unsupported and supported LDOs. The improved thermal stability achieved by use of GO in the LDO/GO hybrids was not affected significantly by the presence of residual sodium. Compared to other LDO supports, GO hybrids were found generally to exhibit higher adsorption capacities per total volume of adsorbent after multiple adsorption-desorption cycles.
- 出版日期2015-7-8
