【作者】 刘璐；

【导师】 何建波；

【作者基本信息】 合肥工业大学 ， 应用化学， 2015， 硕士

【摘要】 氢能是一种理想的能源载体,具有无污染、能量密度高、可实现各类能源的能量转移等优点。电解水可制得高纯度氢气,但因能源消耗大,大规模的实际生产应用受到了很大限制,需要通过开发高催化活性的电极材料来降低析氢过电势。本论文中,在不同基底电极表面分别修饰镍铜纳米合金和2-氨基-5-巯基-1,3,4-噻二唑(AMT),研究两种材料对析氢反应的电催化活性。通过恒电流法在铜基底表面沉积不同原子比的NiCu合金,并测试其在硫酸介质中的催化析氢性能。采用场发射扫描电子显微镜(FE-SEM)和能谱(EDX)技术对合金层的表面形貌和组成进行分析表征,结果表明,所沉积的NiCu合金组成与采用的电流密度直接相关,当电流密度为50 mA cm-2时,NiCu原子比为1:1,呈枝晶状的纳米珍珠链紧密排列。利用线性极化法对析氢电催化活性进行评价,NiCu原子比为1:1时活性最强,交换电流密度比Cu电极提高2836倍,析氢超电势(η50)降低265 mV;比纯Ni的Cu基电极的交换电流密度提高8.5倍,析氢超电势(η50)降低135 mV。由交流阻抗图谱和计时电势数据可知,NiCu纳米合金能显著降低析氢反应的电荷传递电阻,有利于提高活性氢从活性位点的脱附能力。综合分析可知,枝状NiCu纳米晶是具有优越电催化活性的非贵金属析氢催化剂。采用多圈循环扫描伏安法在玻碳电极表面电氧化AMT形成导电聚合物PAMT,并测试其在酸性电解液中的催化析氢性能。对制备的电极材料进行FE-SEM和XPS表征,PAMT薄膜表面均匀致密,表面呈褶皱的短丝状形貌(长度小于100 nm)。经Tafel曲线分析可知,PAMT催化剂使电极开路电势正移约313mV,析氢活化能显著降低；由交流阻抗图谱和计时电势法可以看出,PAMT膜不仅能降低析氢反应的电荷传递电阻,还能有效加快氢原子从电极活性位点的脱除过程。在PAMT薄膜上的析氢活性位可用—N=来表示,其成对出现可满足H-H结合所需。上述分析表明,富含氮、硫原子的导电聚合物作为析氢电催化剂具有广阔的发展前景。不同的基底材料对电催化体系的影响作用不同。为考察不同碳基底电极对修饰PAMT导电聚合物薄膜的析氢性能影响,同样在sCPE电极表面电聚合PAMT薄膜。对比PAMT/sCPE和PAMT/GCE电极在酸性介质下的催化析氢活性,经过比较,在不同基底电极上修饰PAMT薄膜的最佳聚合圈数存在差异；在碳糊电极的最佳聚合圈数为100,而玻碳电极的聚合圈数在60时达到最佳析氢活性,且PAMT/sCPE薄膜电极的交换电流密度是sCPE电极的647倍,活化能提高65%1而PAMT/GCE电极是GCE电极的533倍,活化能提高48%。从上述实验数据分析可知,sCPE基底电极的析氢催化活性在一定程度上要优于GCE电极。更多还原

【Abstract】 Hydrogen is an ideal fuel and energy carrier due to the advantages of no pollution, high energy density, and easy conversion into available energy forms. Highly purified hydrogen can be produced from water electrolysis, but the large-scale electrolysis is reatrained by high energy consumption. Development of synthesizing highly catalytic cathode materials for lowering the overpotential of hydrogen evolution reaction (HER) grew a new impulse to researches. In this article, a study about the electrocatalytic effect of NiCu nanoalloy and 2-Amino-5-mercapto-1,3,4-thiadiazole (AMT) modified on different substrates for HER.Different atom ratio of NiCu nanoalloys were galvanostatically deposited on a Cu substrate for catalyzing HER in H2SO4 electrolytes. The morphology and composition of the deposits were characterized by FE-SEM/EDX analysis. The change of deposition current density resulted in various composition of nanoalloy. The dendrictic NiCu nanopearl chains in 1:1 atom ratio is prepared at the deposition current density of 50 mA cm-2. Dendritic NiCu nanopearl chains in 1:1 atom ratio were galvanostatically deposited on a Cu substrate for catalyzing HER in H2SO4 electrolytes. The morphology and composition of the deposits were characterized by FE-SEM/EDX analysis. All the four-level branches of the dendritic nanoalloy grew in a nanopearl chain structure with a diameter of ca.50-80 nm. The electrocatalytic activity to HER was studied by linear polarization, electrochemical impedance spectroscopy (EIS) and chronopotentiometry. The exchange current density of HER at the NiCu nanoalloy was found to be 2836 and 8.5 times higher than at Cu and Ni/Cu, while the overpotential at a current density of 50 mA cm-2 was decreased by ca.265 and 135 mV relative to Cu and Ni/Cu, respectively. Both the EIS and chronopotentiometry indicate that the NiCu nanoalloy can not only significantly reduce the charge transfer resistance of HER, but also facilitate the elimination of the generated hydrogen from the active sites. This work indicates that the dendritic NiCu nanochains may be a potent candidates as a non-noble metal catalyst for hydrogen energy production.A conductive polymer, poly (2-amino-5-mercapto-1,3,4-thiadiazole) (PAMT), was electrodeposited on a glassy carbon substrate for electrocatalyzing HER in H2SO4 electrolytes. The prepared material was characterized by scanning electron microscope and X-ray photoelectron spectroscopy. The surface of the PAMT film was uniform, crack-free, and was full of curly short filaments (<100 nm long). The free active sites of the PAMT for HER could be represented as -N=,which exist in pairs meeting the dual-site requirements for H-H combination. The Tafel analysis revealed that the open circuit potential was positively shifted by 313 mV due to the PAMT catalyst, with a prominent decrease in activation energy. Both the electrochemical impedance spectroscopy and chronopotentiometry suggested that the PAMT can not only significantly reduce the charge transfer resistance of the HER, but also facilitate the desorption of the generated hydrogen from the active sites. These results indicate that the N- and S-rich conductive polymers deserve further investigation as potential electrocatalyst candidates for hydrogen energy production.Different substrates for electrocatalysis have different effects. A conductive polymer AMT is coated on sCPE and GCE substrate to investigate the effect of different carbon-based supports for HER in acid electrolytes. The distinction with PAMT film deposits by different cycle scans is cleared. PAMT can enhance the exchange current density of HER by 647 times on PAMT/sCPE with the 100 cycle scans of electropolymerization PAMT and PAMT/GCE electrode enhance the exchange current density by 533 times with 60 cycle scans compared to the sCPE and GCE, respectively. Also, PAMT/sCPE can reduce the HER activation energy by 65%, whereas the PAMT/GCE electrode have the lower decrease by 48%. As a result, sCPE may be the better carbon electrode towards GCE as a supports of PAMT polymer film for HER.更多还原