產氫反應在單原子催化劑之反應機構探討

Mechanistic Study of Hydrogen Evolution Reaction on Single Atomic Catalyst

廖振成(Liao Chen-Cheng)

指導教授 ： 蔡明剛 ； 陳韋甫 ； 林麗瓊

國立臺灣師範大學/理學院/化學系/碩士(2019年)

https://doi.org/10.6345/THE.NTNU.DC.005.2019.B05

摘要

陰極的產氫反應在傳統的二電子Volmer–Tafel–Heyrovský模型已被使用了數十年，在這些反應中，電化學脫氫的步驟包含了吸附態的氫、質子及電子，然而，從吸附態的氫到產生氫氣的過程並沒有被仔細描述，實驗上我們成功地合成了單原子鉑催化劑，發現了其在產氫反應上與鉑塊材有顯著的差異，因此我們透過理論計算模擬單原子鉑催化劑的產氫反應，並在計算的過程中發現了新的中間體，根據這些計算的結果，與動力學模型結合後，可以推導出電流及過電位的關係式，在這個關係式裡頭我們做了Tafel斜率的分析，透過推導的Tafel斜率與實驗的Tafel斜率比較，我們得到了很高的一致性。
根據在單原子鉑催化劑的例子，我們再次透過理論計算來預測不同單原子過度金屬催化劑在產氫反應的表現，並再次結合動力學模型，可以得到不同的反應機制，並推導出了不同金屬的Tafel斜率，以提供實驗針對產氫催化劑選擇的指引。

關鍵字

HER ； SAC ； DFT ； Tafel

並列摘要

The classic two-electron-reaction Volmer–Tafel–Heyrovský models in the cathodic hydrogen evolution reaction (HER) have been adopted for decades. Electrochemical desorption of hydrogen involves simply a Pt-H, a proton (or a hydronium ion) and an electron in the step. However, it was not clearly described how the second hydrogen atom attaches to Pt-H and form hydrogen molecule. With the possibility of preparing isolated atomic Pt, we report a new dihydride mechanism occurs through the formation of an intermediate dihydride state on single atomic platinum and in turn generates the Kubas-type intermediate. We present that mechanistic models built by the energy diagram of DFT calculation. Combining with DFT results and kinetic model, we successfully derived equations from the proposed mechanisms. The Tafel slope from the derived equation is consistent to the experimentally measured Tafel slope which evidenced the presence of the new dihydride mechanism.
Based on the results in Pt single atomic catalyst (SAC), we also calculated HER on single atomic catalyst for d7, d8 and d9 transition metals. Combing with kinetic model, we proposed specific mechanisms and derived the equations for Tafel slopes. This information could provide a guidance for experiment to select a catalyst for HER.

並列關鍵字

HER ； SAC ； DFT ； Tafel

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