Aligholivand Mehri, Shaghaghi Zohreh, Bikas Rahman, Kozakiewicz Anna
Coordination Chemistry Research Laboratory, Department of Chemistry, Faculty of Science, Azarbaijan Shahid Madani University P.O. Box 83714-161 Tabriz Iran
Department of Chemistry, Faculty of Science, Imam Khomeini International University 34148-96818 Qazvin Iran.
RSC Adv. 2019 Dec 6;9(69):40424-40436. doi: 10.1039/c9ra08585h. eCollection 2019 Dec 3.
A new mononuclear Ni(ii) complex, NiL (1), was synthesized from the reaction of Ni(OAc)·4HO and salophen-type NO-donor ligand, HL (where HL = 2,2'-((1,1')-((4-chloro-5-methyl-1,2-phenylene)bis(azanylylidene))bis(methanylylidene))diphenol), in ethanol. The obtained complex was characterized by elemental analysis, spectroscopic techniques and single crystal X-ray analysis. The complex was studied as a water oxidizing catalyst and its electrocatalytic activity in the water oxidation reaction was tested in 0.5 M of borate buffer at pH = 3, 7 and 11 in a typical three-electrode setup with a carbon paste electrode modified by complex 1 as a working electrode. The linear sweep voltammetry (LSV) curves indicated that complex 1 has a much superior activity and only needs 21 mV Ag/AgCl overvoltage to reach a geometrical catalytic current density of 2.0 mA cm at pH = 11. The onset potential decreased from 1.15 V to 0.67 V Ag/AgCl with an increase of pH from 3 to 13 under a constant current density of 1.0 mA cm. Then, to determine the true catalyst for the water oxidation reaction in the presence of complex 1 at pH = 3, 7 and 11, cyclic voltammetry was also performed. The continuous CVs for complex 1 at neutral and alkaline solutions showed significant progress for the water oxidation reaction. In addition, the amperometry tests exhibited excellent stability and high constant current density for water oxidation by CPE-complex 1 under electrochemical conditions at pH = 11 and 7. Although X-ray powder diffraction analysis did not show a pure and crystalline structure for NiO , the scanning electron microscopy images showed that nickel oxide at pH = 11 and nickel oxide or other Ni-based compounds at pH = 7 are true water oxidizing catalysts on the surface of a CPE electrode. Moreover at pH = 3, no clear water oxidation or NiO formation was observed.
通过在乙醇中使Ni(OAc)·4H₂O与沙罗芬型NO供体配体HL（其中HL = 2,2'-((1,1')-((4-氯-5-甲基-1,2-亚苯基)双(氮亚基))双(亚甲基))二苯酚）反应，合成了一种新型单核Ni(ii)配合物NiL (1)。通过元素分析、光谱技术和单晶X射线分析对所得配合物进行了表征。将该配合物作为水氧化催化剂进行研究，并在典型的三电极装置中，以经配合物1修饰的碳糊电极作为工作电极，在pH = 3、7和11的0.5 M硼酸盐缓冲溶液中测试其在水氧化反应中的电催化活性。线性扫描伏安法(LSV)曲线表明，配合物1具有优异得多的活性，在pH = 11时仅需21 mV（相对于Ag/AgCl）的过电压即可达到2.0 mA cm²的几何催化电流密度。在1.0 mA cm²的恒定电流密度下，随着pH从3增加到13，起始电位从1.15 V（相对于Ag/AgCl）降至0.67 V（相对于Ag/AgCl）。然后，为了确定在pH = 3、7和11时存在配合物1的情况下水氧化反应的真正催化剂，还进行了循环伏安法。配合物1在中性和碱性溶液中的连续循环伏安曲线显示水氧化反应有显著进展。此外，安培法测试表明，在pH = 11和7的电化学条件下，CPE-配合物1对水氧化具有优异的稳定性和高恒定电流密度。尽管X射线粉末衍射分析未显示出纯的和结晶的NiO结构，但扫描电子显微镜图像表明，pH = 11时的氧化镍以及pH = 7时的氧化镍或其他镍基化合物是CPE电极表面真正的水氧化催化剂。此外，在pH = 3时，未观察到明显的水氧化或NiO形成。
