Phosphorus and Nitrogen Dual-doped Graphene Oxide as Metal-free Catalyst for Hydrogen Evolution Reaction

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Title:	Phosphorus and Nitrogen Dual-doped Graphene Oxide as Metal-free Catalyst for Hydrogen Evolution Reaction
Authors:	陳威廷;Chen, Wei-Ting
Contributors:	機械工程學系
Keywords:	石墨烯;析氫反應;協同作用
Date:	2020-04-21
Issue Date:	2020-06-05 17:43:17 (UTC+8)
Publisher:	國立中央大學
Abstract:	碳材料催化劑有潛力應用於電化學中的析氫反應（HER）來產生氫氣做為能源，尤其石墨烯其能隙結構可藉由摻雜不同的元素來降低析氫反應所需的活化能，當摻雜多個不同元素下還能產生協同作用，進一步提升其析氫反應的活性。本實驗採用了兩步合成的方法來製備磷（P）-氮（N）雙摻雜氧化石墨烯，第一步以水熱法先摻雜磷元素後，接著第二步再高溫退火時通入氨氣摻雜氮元素已完成製備，不同條件下的參數命名為 (NP-溫度 PA X，例如NP-1000 PA 4 為第一步水熱法氧化石墨烯溶液(GO)與植酸(PA)的比例為15 mL/4 mL，退火溫度在1000度的條件下通入氨氣完成製備)。在探討析氫反應的活性中，本實驗改變了磷的前驅物濃度及不同的退火溫度來找到最佳參數，關於磷的前驅物濃度，發現到隨著磷元素摻雜的增加，即使氨氣的量一樣，其氮摻雜的量也會增加;在不同退火溫度800度、900度、1000度的探討中，900度的退火溫度有最高的摻雜原子量，其含有9.8 ％的氮元素和4.8 ％的磷元素，但是在析氫反應的電化學測式中，1000度的退火溫度條件有最好的析氫反應， NP-1000 PA 4中的原子摻雜比率是6.7 ％的氮和4 ％的磷，其原因為1000度退火溫度下，氧化石墨烯的還原程度較高，電阻較低，即使元素摻雜的比例較低，其析氫反應的活性仍較900度的好，NP-1000 PA 4表現出的析氫反應只需施加過電壓為338 mV就能達到10 mA/cm2 電流密度，Tafel斜率為88 mV / dec和Rct 32 Ω，因此，磷氮摻雜的氧化石墨烯未來有希望作為析氫反應的活性材料。;Carbon-based catalysts are promising for electrochemical hydrogen evolution reaction (HER). The bandgap of graphene can be tailored through the doping processes and resulting in a synergistic coupling effect. Herein, two-step synthesis phosphorus(P)-nitrogen(N) dual doped graphene oxide was prepared, followed by annealing at different temperatures to explore the catalyst effect for HER applications. Green phosphorus precursor phytic acid and nitrogen precursor ammonia gas were used in this experimental work. The heteroatom doping concentrations were studied and discussed. The doping level of phosphorus in the first step was found to enhance the nitrogen doping effect in the second step. The highest doping atomic ratio was achieved in the sample NP-900 PA 4 with 9.8% N and 4.8 %P. The annealing process at different temperatures was used for finding an optimized condition in order to reduce graphene oxide while maintaining the active sites in graphene structure. The atomic doping ratio in NP-1000 PA was 6.7% nitrogen and 4% phosphorus. Also, NP-1000 PA 4 displayed superior HER performance with an overpotential of 338 mV (10 mA/cm2), Tafel slope of 88 mV/dec, and Rct of 32 Ω. Therefore, there is a great potential to use such dual doped graphene as an efficient catalyst for the future hydrogen energy system.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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