双二苯基-1-甲基咪唑膦氯化镍的制备及其电催化还原CO2的研究

以二苯基-1-甲基咪唑膦（dpim）为配体制备了一种新型的配合物催化剂Ni(dpim)₂Cl₂. 循环伏安研究表明，Ni(dpim)₂Cl₂配合物在氮气气氛下表现出两步还原的电化学行为，在-0.7 V下为两电子的不可逆还原，在-1.3 V下为单电子准可逆还原. 向电解液中通入CO₂后，在-1.3 V下的还原峰变得不可逆，且其峰电流从0.48 mA·cm^-2增大到0.55 mA·cm^-2. 在质子源（CH₃OH）存在的条件下，该还原峰电流可继续增大到0.72 mA·cm^-2. 该研究结果表明，Ni(dpim)₂Cl₂配合物对CO₂还原具有良好的电催化性能，且其电催化还原过程符合ECE机理. 在-1.3 V下恒电位电解得到的还原产物主要为CO，催化转换频率（Turnover of Frenquency, TOF）为0.17 s^-1.

Preparation of Ni(dpim)2Cl2 Complex for the Electrocatalytic Reduction of CO2

A newNi(dpim)₂Cl₂complex using 2-(diphenylphosphino)-1-methylimidazole (dpim) as ligand was prepared and served as a catalyst for the electrochemical reduction of CO₂. The electrochemical redox behavior ofNi(dpim)₂Cl₂ in CH₃CN/TPABF₄ solution under nitrogen atmosphere showed the two-electron irreversible reduction at -0.7 V and one-electron quasi-reversible reduction at -1.3 V. After bubbling CO₂ into the electrolyte, the reduction peak appeared at -1.3 V became irreversible andthe peak current increased from 0.48 mA·cm^-2 to 0.55 mA·cm^-2. Moreover, the peak current at -1.3 V could further increase to 0.72 mA·cm^-2 in the presence of proton source (CH₃OH). These observations indicate thatthe Ni(dpim)₂Cl₂exhibited a good electrocatalytic performance toward CO₂ reduction and the electrocatalytic reduction processfollowed the ECE mechanism. The reduction products obtained by the potentiostatic electrolysis (at -1.3 V) were identified to be mainly CO with the catalytic conversion frequency of 0.17 s^-1.