热处理对ZnOHF电催化还原CO2制CO的性能影响

Effect of heat treatment on the performance of ZnOHF for electrocatalytic reduction of CO2 to CO

  • 摘要: 利用电化学方法将惰性CO2选择性和高效地转化为增值化学品是缓解环境和能源危机的重要途径之一。非贵金属Zn因储量丰富、价格低廉且稳定无毒常用于电催化CO2还原(CO2RR)制CO过程。本研究采用水热法制备了ZnOHF粉体并通过热处理对其进行活化。分别采用XRD、SEM、EDS和XPS表征方法对热处理前后ZnOHF的结构、形貌和元素分布进行研究。相比未经过热处理的ZnOHF样品,热处理后的ZnOHF样品在电催化还原CO2合成CO的反应中表现出更高的CO2还原活性和对CO的选择性,其CO的法拉第效率达到77.4%,这是由于热处理可使ZnOHF表面获得适宜数量的羟基,减小颗粒粒度,增加粗糙度和电化学比表面积(ECSA),从而暴露更多的活性位点,促进CO2在表面的吸附活化以及CO脱附。

     

    Abstract: The selective and efficient conversion of inert CO2 into value-added chemicals by electrochemical methods is one of the important ways to alleviate the environmental and energy crisis. Non-precious metal Zn is often studied in electrocatalytic CO2 reduction reaction (CO2RR) to CO because of its abundant reserves, low price and good stability. However, it is still necessary to improve the catalytic performance of traditional Zn-based catalysts for CO2RR. In order to optimize the performance of Zn-based catalysts, the pure ZnOHF sample was synthesized by hydrothermal method. The effect of heat treatment on the structure, texture and electrocatalytic CO2RR performance of ZnOHF samples was studied. The electrocatalytic evaluation results show that the heat-treated ZnOHF sample gives better CO2RR activity and CO selectivity compared with untreated sample, the Faraday efficiency of CO (FECO) reaches 77.4% at −1.15V vs. RHE. And even at a potential of −1.05 V vs. RHE its current density and FECO can be stabilized at −6.17 mA/cm2 and 72% in 5 h. This is because heat treatment can make the surface of ZnOHF obtain appropriate hydroxyl amount, the microcrystalline particles become uniform and fine, and the roughness and electrochemical specific surface area (ECSA) increase, thus exposing more active sites and promoting the adsorption and activation of CO2 on the surface and CO desorption. This provides experimental basis and theoretical guidance for the design and development of Zn-based catalysts for electrocatalytic CO2RR.

     

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