利用新能源电能电催化还原二氧化碳(CO2)技术能在减排降碳过程将CO2转化为增值化学品,有广阔应用前景,在多种还原产物中,甲酸(HCOOH)易储存和运输,储氢密度高,应用前景好.氧化锡(SnO2)电催化材料成本低、毒性小,且SnO2用于电催化还原CO2制HCOOH选择性高.而在电催化还原的工业化中,合理的电解池结构有重要意义.为探究更合理的电解池结构,提出一种自制的多层堆栈式电解池,将通过火焰喷雾热解方法制备的SnO2纳米颗粒作为电催化剂,进行电催化还原CO2研究.探究电解池的阴极-阳极间距、电解液流速、电解液浓度及电极堆栈数目等参数对电催化性能影响.试验结果显示:阴极-阳极距离越小,电能损耗越少,电催化还原CO2性能更佳;电解液的流速对催化剂还原性能无明显影响,但过大的流速使反应的电流密度产生大的波动;在电解液浓度小于1 mol/L时,催化剂对HCOOH的选择性随着电解液浓度增加而增加,而在电解液浓度大于1 mol/L时,各产物的选择性趋于稳定;电极堆栈排放时,电流密度略下降,但整体法拉第效率和HCOOH的法拉第效率均所提高,并对析氢反应有较明显抑制作用.使用堆栈电解池可减小电荷转移电阻及扩散电阻.对于该堆栈电解池,在阴极-阳极间距10 mm、施加电位-1.2 V vs.RHE、KHCO3浓度1 mol/L下,SnO2在堆栈条件对HCOOH的法拉第效率达37.53％,且总的法拉第效率达75.83％.结果表明:使用堆栈电解池可提升催化剂催化性能,提升目标产物的选择性.
Experimental study of electrocatalytic CO2 reduction by nano-SnO2 based on stacked electrolytic reactor
The electrocatalytic reduction of carbon dioxide(CO2)using new energy and electrical energy can convert CO2 into value-add-ed chemicals while reducing carbon emissions,which has broad application prospects.Among the various reduction products,formic acid(HCOOH)is easy to store and transport,with a high storage density of hydrogen.Tin oxide(SnO2)electrocatalytic materials are low-cost and less toxic,while SnO2 is highly selective for HCOOH when used for electrocatalytic reduction of CO2.In the industrialization of electrocatalytic reduction,a reasonable electrolytic reactor structure is of great significance.To explore a more reasonable electrolytic re-actor structure,this paper proposes a homemade multilayer stacked electrolytic reactor,in which SnO2 nanoparticles prepared by flame spray pyrolysis method are used as electrocatalysts for electrocatalytic reduction of CO2.The effects of parameters such as cathode-anode spacing,electrolyte flow rate,electrolyte concentration and the number of electrode stacks on the electrocatalytic performance of the elec-trolytic cell were investigated.The experimental results show that:the closer the cathode-anode distance is,the lower the electrical energy loss is,and the catalyst has better catalytic performance;the flow rate of the electrolyte has no significant effect on the reduction perform-ance of the catalyst,but when the flow rate is too fast,the current density of the reaction produces a more drastic fluctuation.When the electrolyte concentration was less than 1 mol/L,the selectivity of the catalyst for HCOOH increased with the increase of the electro-lyte concentration,whereas the selectivity of the catalyst for each product stabilized at the electrolyte concentration of more than 1 mol/L.The current density decreased slightly when the electrodes were placed in stacks,but the overall Faraday efficiency and the Faraday effi-ciency of HCOOH both increased,and the hydrogen precipitation reaction was suppressed more significantly.The charge transfer resistance and diffusion resistance were reduced when using a stack electrolytic reactor.The optimum Faraday efficiency for HCOOH of SnO2 under stack conditions reaches 37.53％and the total Faraday efficiency reaches 75.83％with the cathode-anode spacing of 10 mm,the applied potential of-1.2 V vs.RHE,and the KHCO3 concentration of 1 mol/L.The results indicate that the catalytic per-formance of the catalyst and the selectivity of the target products can be enhanced by using a stacked electrolytic reactor.
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