Lu Guang, Wang Hui, Bian Zhao-Yong, Liu Xin
J Nanosci Nanotechnol. 2014 Sep;14(9):7097-103. doi: 10.1166/jnn.2014.8952.
Palladium-graphene nanocomposites catalysts for the conversion of CO2 to formic acid were prepared by means of sodium borohydride reduction of K2PdCl4 in a graphite oxide suspension, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV) technologies. The characterization results showed that graphene with a d-spacing of 3.82 Å was fabricated, and palladium nanoparticles with an average size of 3.8 nm were highly dispersed in the graphene sheets with amorphous structure. The cyclic voltammogram analyses indicated palladium-graphene nanocomposites catalysts posed high catalytic activity for the CO2 reduction and the rate-determining step was the CO2 diffusion process from bulk solution to electrode surface. Then the electrocatalytic reduction of CO2 was investigated in a diaphragm electrolysis device, using Pd/graphene gas-diffusion electrode as a cathode and a Ti/RuO2 net anode. The reduction process was optimized by the application of factorial design 2(3) (voltage, reaction time and electrolyte concentration) and response surface methodology (RSM). Optimum conditions for the production of formic acid were given as following: voltage: 5.1 V, reaction time: 50.4 min and electrolyte concentration: 0.5 mol L(-1). The yield of formic acid formation was 3157.7 mg L(-1) and Faraday efficiency was 86.9% under the optimum operation condition.
通过在氧化石墨悬浮液中用硼氢化钠还原K2PdCl4制备了用于将CO2转化为甲酸的钯-石墨烯纳米复合催化剂，并采用X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）和循环伏安法（CV）技术对其进行了表征。表征结果表明，制备出了d间距为3.82 Å的石墨烯，平均尺寸为3.8 nm的钯纳米颗粒高度分散在具有非晶结构的石墨烯片中。循环伏安分析表明，钯-石墨烯纳米复合催化剂对CO2还原具有高催化活性，速率决定步骤是CO2从本体溶液扩散到电极表面的过程。然后，在隔膜电解装置中，以Pd/石墨烯气体扩散电极作为阴极、Ti/RuO2网状电极作为阳极，研究了CO2的电催化还原。通过应用2(3)析因设计（电压、反应时间和电解质浓度）和响应面方法（RSM）对还原过程进行了优化。生成甲酸的最佳条件如下：电压：5.1 V，反应时间：50.4 min，电解质浓度：0.5 mol L(-1)。在最佳操作条件下，甲酸生成产率为3157.7 mg L(-1)，法拉第效率为86.9%。
