以密度泛函理論計算改良鹼性析氫反應之描述符

Abstract

在過去的研究中，酸性的析氫反應只需計算氫的吸附自由能(∆GH*)，即可決定催化劑的好壞。在本篇研究中，我們利用3個鹼性析氫反應中最重要的參數：氫的吸附自由能(∆GH*)、氫氧根的吸附自由能(∆GoH*)、水解離活化能(Ea(water))，繪製出雷達圖，建構出一個簡單、有用的方法，來判斷較為複雜的鹼性析氫反應活性。一開始，本篇研究先計算單金屬銀(Ag)、金(Au)、鈷(Co)、銅(Cu)、鎳(Ni)、鈀(Pd)、鉑(Pt) (皆為FCC (111)面)，並數繪製成雷達圖，與文獻值的交換電流密度對數(log i0)繪製成散佈圖後，發現兩者呈現高度正相關，代表雷達圖面積可以很好的對應鹼性析氫反應的活性。接著，本篇研究測試了以鉑(Pt)和鈀(Pd)為基底的雙金屬催化劑：Pt3M、PtM、Pd3M、PdM (M = Ag、Au、Co、Ni、Pd、Pt、Rh、Ru)，並且將雷達圖面積與功函數比較後，發現兩者呈線高度正相關，代表功函數也可以代表活性，並且以鉑(Pt)為基底的雙金屬催化劑的活性高於以鈀(Pd)為基底的雙金屬催化劑，其中又以Pt3Au為最高。最後，本篇研究也計算了非金屬催化劑Fe3O4(220)及FeP(111)，繪製出雷達圖後，其活性趨勢為FeP(111)> Fe3O4(220)，與實驗中磷化物的活性高於氧化物的趨勢相符。Catalytic activity of hydrogen evolution reaction (HER) in acidic media can be well predicted through hydrogen-adsorption free energy (∆GH*) previously. In the present study, we further develop a simple and useful method to diagnose the more complicated HER in alkaline media by utilizing three vital parameters of ∆GH*, hydroxide-adsorption free energy (∆GoH*), and activation energy of water dissociation (Ea(water)) in a radar chart. First, we examined single metals of Ag, Au, Co, Cu, Ni, Pd, Pt with the same crystal structure (FCC) and surface facet (111). The area of radar chart well correlated with the (logarithm of) exchange current density (log i0) from experiments, indicating the accuracy of our new method. Further, we examined Pt and Pd-based bimetallic catalysts of Pt3M, PtM, Pd3M and PdM (M = Ag, Au, Co, Ni, Pt, Pd, Rh, Ru). Excellent correlation is also found between the area and work function, representing as activity. Pt-based bimetals shows better activity than Pd-based one and Pt3Au shows the best HER activity. Finally, Fe3O4(220) and FeP(111) have been examined to extend our method in non-metallic catalysts. The predicted activity follow the trends of FeP(111)> Fe3O4(220), which consistent with the experiments that phosphides are more active than oxides.