鈷、鎳以及鈷鎳合金薄膜電極材料製備及其產氫活性的研究

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题名:	鈷、鎳以及鈷鎳合金薄膜電極材料製備及其產氫活性的研究
作者:	王彥貞;Wang, Yen-Chen
贡献者:	化學學系
关键词:	鈷;鎳;鈷鎳合金;氫氣析出反應;cobalt;nickel;cobalt-nickel alloy;hydrogen evolution reaction
日期:	2021-08-18
上传时间:	2021-12-07 11:23:20 (UTC+8)
出版者:	國立中央大學
摘要:	本研究以循環掃描電位的方式，於Au(111)或Pt(111)上沉積鈷、鎳以及不同比例的鈷鎳合金後，於鹼性溶液中(0.1M KOH)測試對氫氣析出反應(hydrogen evolution reaction,HER)之催化活性，而合金中鈷鎳的比例以角解析X射線光電子光譜(ARXPS)來分析，並藉由STM觀察這些金屬的沉積過程與表面形貌。其中CoNi6.1/Au(111)合金電極擁有較小的過電位(-223mV)以及Tafel斜率(87.7mV/dec)，對產氫(HER)活性優於純鈷、鎳以及其他比例的合金。於Pt(111)上修飾3層Ni後，其HER活性表現最突出，它有最小的過電位(-53mV)，以Tafel斜率(46.9mV/dec)推論， HER的速率決定步驟(rds)為氫氣脫附反應(Heyrovsky步驟)，其餘材料的rds皆為氫吸附的反應(Volmer步驟)，可能是由於Ni能有利於水的分解，而三層的鎳與白金之間可能有很好的電子效應，能夠提供有利於氫的吸附位點，且OHad與Ni之間的相互作用最為理想，因此大幅提升產氫活性。以STM觀察鈷鎳合金於Au(111)上成長，第一層多以針狀的方式生長為無序或整齊的moir? pattern結構。在Pt(111)上，鈷鎳離子比例為1:1時，第一層沉積膜由兩種金屬共同組成，無整齊的蜂窩狀結構，當鈷鎳比例為1:4時，第一層亦無整齊的蜂窩狀結構，而是長成樹枝狀的樣貌。也以STM觀察pH3與pH5硫酸鹽中，鎳在Au(111)和Pt(111)上的生長。;The electrodeposition of cobalt, nickel and cobalt-nickel alloys on Au(111) and Pt(111) electrodes was studied by using cyclic voltammetry (CV),scanning tunneling microscope (STM) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activities of the as-prepared filmy materials toward hydrogen evolution reaction (HER) were examined in alkaline media (0.1 M KOH). The chemical compositions of the Co-Ni alloys were analyzed with angle-resolved X-ray photoelectron spectroscopy (ARXPS).The deposition process and surface morphology of these metallic films were observed by STM. The Au(111)-supported CoNi6.1 alloy film exhibited higher HER activity than pure cobalt, nickel and the other alloys, as manifested by a smaller overpotential (-223 mV) and Tafel slope (87.7 mV/ dec). On the Pt(111) electrode the deposition of three monolayer (ML) Ni led to the most active catalyst for HER, as evaluated from the smallest overpotential (-53 mV) and Tafel slope (46.9 mV/dec). This catalyst was unique, in that the rate-determining step (rds) for HER was the hydrogen desorption reaction, as opposed to the hydrogen adsorption reaction found for others. It is assumed that as-preapred Ni films were active sites for the water splitting reaction, which facilitated dissociation of water molecule to OHad. It is assumed that Pt substrate altered the electronic configuration of the three-layer-thick nickel film, which optimized its interaction of H and OH.The first layer of the depositied Co-Ni alloys on Au(111) assumed a needle-like texture, disordered and ordered moir? patterns, which resemble those features observed with pure Ni deposit. The Co-Ni alloy films deposited on Pt(111) from a 1:1 and 1:4 Co2+/Ni2+ solutions had a disordered structure and a dendritic pattern. The latter resulted from a fractal-like growth mode. The electrodeposition of Ni on Au(111) and Pt(111) in pH 3 and pH 5 sulfate media were also examined.
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