高催化活性M-BHT(M=Co， Cu)电催化还原CO2为CH4的密度泛函理论研究

具有独特电子结构和丰富催化位点的二维金属有机框架材料是具有高活性的CO₂还原反应的电催化剂. 本文基于密度泛函理论(DFT)计算, 发现单层Co-BHT(BHT=benzenehexathiol, 苯六硫醇)将CO₂还原为CH₄时具有很高的催化活性. 吉布斯自由能变化计算结果表明, 在Co-BHT上将CO₂还原成CH₄的最佳反应路径为CO₂→^*COOH→^*CO→^*CHO→^*CHOH→^*CH→^*CH₂→^*CH₃→CH₄; 整个反应的速度控制步骤为^*CO→^*CHO; 速度控制步骤的吉布斯自由能变化(ΔG_L)为0.66 eV, 比在二维Cu-C₃N₄(ΔG_L=0.75 eV)和传统的Cu(211) 表面(ΔG_L=0.74 eV) 将CO₂还原为CH₄的吉布斯自由能变化都小. 而在单层Cu-BHT表面的反应路径和速度控制步骤 (CO₂→^*COOH)与Co-BHT均不同, 且ΔG_L为0.76 eV. 与Cu-BHT相比, Co-BHT将CO₂还原为CH₄的ΔG_L更低, 这可能归因于Co-BHT的d能带中心高于Cu-BHT, 导致Co-BHT与中间体的相互作用更强.

Density Functional Theoretical Studies on the Promising Electrocatalyst of M-BHT(M=Co or Cu)for CO2 Reduction to CH4

Two-dimensional metal organic frame materials show excellent electrocatalytic activity for CO₂ reduction reaction because of their unique electronic structures and abundant catalytic sites.Herein,based on density functional theory calculations,we found that monolayer Co-BHT(BHT=benzenehexathiol)exhibits promising electrocatalytic activity in CO₂ reduction to CH4.The Gibbs free energy change calculations reveal that the optimal reaction path of CO₂ reduction to CH4 on Co-BHT is CO₂→^*COOH→^*CO→^*CHO→^*CHOH→^*CH→^*CH₂→^*CH₃→CH₄,with the rate-limiting step of^*CO→^*CHO.The Gibbs free energy change of the rate-limiting step(ΔG_L)is 0.66 eV,lower than that on both 2D Cu-C₃N₄(ΔG_L=0.75 eV)and traditional Cu(211)(ΔGL=0.74 eV).Furthermore,the studies for monolayer Cu-BHT were also carried out,where the optimal reaction path is different,and the rate-limiting step is CO₂→^*COOH with theΔG_L of 0.76 eV.The lowerΔG_L of CO₂ reduction on Co-BHT than that on Cu-BHT may be attributed to its higher d-band center compared with that of Cu-BHT,which leads to stronger interactions with the intermediates.Our work predicts the promising electrocatalytic activity of Co-BHT and provides useful insights into the catalytic mechanism and performance of Metal-BHT for CO₂ reduction to CH₄.