调控CuO表面性质选择性电催化还原CO_(2)制HCOOH

Modulation of CuO Surface Properties for Selective Electrocatalytic Reduction of CO_(2) to HCOOH

电催化二氧化碳还原反应可将温室气体二氧化碳转化为化工原料或者有机燃料,为克服全球变暖和电能向化学能转化提供了一条可行途径。该技术的主要挑战是产物分布广,导致单一产物选择性低,而调控催化剂的表面性质是解决这一难题的可行策略。本研究通过对氧化亚铜、硫化亚铜进行氧化制备表面性质不同的氧化铜,其中,氧化硫化亚铜制得的CuO-FS催化剂提高了电还原二氧化碳的活性和还原产物甲酸的选择性。该催化剂表现出较高的总电流密度,而且在一个较大的测试电压范围(-0.8~-1.1V)内,甲酸的法拉第效率可以保持在70%以上,在-0.9V时达到最大值78.4%。反应机理探究表明,CuO-FS优异的电还原二氧化碳性能归因于其较大的电化学活性表面积提供了大量表面活性位点,产生较高的总电流密度;而且电催化过程中催化剂表面产生较少的零价Cu,减少了乙烯的生成,使产物更集中于甲酸。

The electrocatalytic carbon dioxide reduction reaction can convert the greenhouse gas carbon dioxide into chemical raw materials or organic fuels, providing a feasible way to overcome global warming and the conversion of electrical energy to chemical energy. The main challenge of this technology is the wide product distribution, resulting in low selectivity of a single product, however, modulating the surface properties of the catalyst is an efficient strategy to solve this problem. In this study, the precursors of Cu_(2)O and Cu_(2)S were oxidized to the CuO catalysts with different surface properties. The CuO-FS catalyst derived from Cu_(2)S delivered the improved activity of electro-reduction of carbon dioxide and selectivity for formic acid product. This catalyst exhibited a higher total current density and the Faraday efficiency of formic acid > 70% in a wide test voltage range of -0.8 - -1.1 V;the Faraday efficiency for formic acid could reach a maximum of 78.4% at -0.9 V. The mechanism study indicated that the excellent performance of CuO-FS for electro-reduction of carbon dioxide could be attributed to the large electrochemically active surface area,which provided a large number of surface active sites, resulting in a higher total current density;moreover, the less zero-valent Cu was produced over the surface of CuO-FS during the electrocatalytic process, which reduced the production of ethylene and thus promoted the production of formic acid.