电催化CO_(2)还原耦合HCHO氧化反应系统促进污染物同步经济高效资源化转化

Paired Electrochemical CO_(2) Reduction and HCHO Oxidation for the Cost-Effective Production of Value-Added Chemicals

传统电化学CO_(2)还原(CO_(2)RR)系统中阳极发生的水氧化半反应(WOR)具有动力学缓慢、过电位大、能耗高等缺点,限制了CO_(2)RR系统的经济效益和应用。因此,本研究引入MnO_(2)阳极进行甲醛氧化半反应(FOR)以代替WOR,构建了一种新型CO_(2)RR/FOR耦合系统。与传统的CO_(2)RR/WOR系统相比,在相同的施加电势下,CO_(2)RR/FOR耦合系统的CO_(2)RR电流密度和CO_(2)RR产物的生成速率通常更具有优势。此外,在CO_(2)RR/FOR耦合系统中,在合适的施加电势下,HCHO可以选择性地转化为HCOOH。具体来说,两电极CO_(2)RR/FOR耦合系统中,在3.5V的槽电压下,近90%的HCHO可以被去除,且HCHO会选择性转化为HCOOH,其转化率约为48%。更重要的是,在不同的工作电流下,FOR所需的电势比WOR所需的电势要小。在-10 mA·cm^(-2)时,CO_(2)RR/FOR耦合系统能降低约210 mV的槽电压,并且其能耗比单独的CO_(2)RR系统和FOR系统的能耗之和降低45.13%。值得注意的是,当使用商业多晶硅太阳能电池作为电源时,在CO_(2)RR/FOR耦合系统中的CO_(2)RR电流密度、CO_(2)RR产物的生成速率和HCHO到HCOOH的选择性仍然可以实现相当的改善。目前的工作将进一步推动研究开发新型的CO_(2)RR耦合系统,以经济有效地将CO_(2)和有机污染物同时转化为有价值的化学品。

Due to rapid industrial development and human activities,CO_(2) emissions have led to serious environmental/ecological problems and climate changes such as global warming.Due to this situation,achieving carbon neutrality has become an urgent mission to improve the future of mankind.The use of the electrocatalytic CO_(2) reduction reaction(CO_(2)RR)to produce higher-value fuels and chemicals is an effective strategy for reducing CO_(2) emissions and easing the energy crisis.The water oxidation half-reaction(WOR),which occurs at the anode in a traditional CO_(2) RR system,typically suffers from slow kinetics,a large overpotential,and high energy consumption.The organic pollutant formaldehyde(HCHO)is oxidized into industrial materials(such as formic acid)under neutral conditions,which is of great significance for the sustainable production of energy and lessening environmental pollution.In addition,the number of electron transfers involved and the required potential for the HCHO oxidation half-reaction(FOR)are smaller than those of WOR,suggesting that FOR could potentially replace WOR as a coupling reaction with CO_(2) reduction.In this study,FOR at a MnO_(2)/CP anode is introduced to produce a novel paired CO_(2)RR/FOR system.The current density and generation rate of CO_(2)RR products in this paired CO_(2)RR/FOR system are generally larger than those of conventional CO_(2)RR/WOR systems at the same applied potential.Moreover,in paired CO_(2)RR/FOR systems,HCHO can be selectively converted into HCOOH at certain applied potentials.Nearly 90% of the HCHO can be selectively converted to HCOOH with a conversion efficiency of about 48%at a cell voltage of 3.5 V in a two-electrode paired CO_(2)RR/FOR system.More significantly,under a different working current,the potentials required for FOR are systemically smaller than those for WOR.At−10 mA∙cm−2,the cell voltage of the paired CO_(2)RR/FOR system can be reduced by 210 mV,and the required electric energy for the paired CO_(2)RR/FOR system can be reduced by 45.13% compared with the sum of single CO_(2)RR and FOR systems.Notably,when a commercial polysilicon solar cell is used as the power supply,improvements in the current density,the generation rate of CO_(2)RR products,and the HCHO to HCOOH selectivity can be still achieved in the paired CO_(2)RR/FOR system.The present work will inspire further studies for developing novel paired CO_(2)RR systems for the cost-effective,simultaneous conversion of CO_(2) and organic pollutants into valuable chemicals.