Faculty of Non-Ferrous Metals, AGH University of Science and Technology in Kraków, Mickiewicza 30 Ave., 30-059 Krakow, Poland.
Department of Materials Science, Graduate School of Engineering Science, Akita University, Akita 010-8502, Japan.
Int J Mol Sci. 2023 Feb 14;24(4):3836. doi: 10.3390/ijms24043836.
Ni coatings with high catalytic efficiency were synthesised in this work, obtained by increasing the active surface and modifying Pd as a noble metal. Porous Ni foam electrodes were obtained by electrodeposition of Al on a nickel substrate. Deposition of Al was carried out with potential -1.9 V for a time of 60 min in NaCl-KCl-3.5 mol%AlF molten salt mixture at 900 °C, which is connected with the formation of the Al-Ni phase in the solid state. Dissolution of Al and Al-Ni phases was performed by application of the potential -0.5 V, which provided the porous layer formation. The obtained porous material was compared to flat Ni plates in terms of electrocatalytic properties for ethanol oxidation in alkaline solutions. Cyclic voltammetry measurements in the non-Faradaic region revealed the improvement in morphology development for Ni foams, with an active surface area 5.5-times more developed than flat Ni electrodes. The catalytic activity was improved by the galvanic displacement process of Pd(II) ions from dilute chloride solutions (1 mM) at different times. In cyclic voltammetry scans, the highest catalytic activity was registered for porous Ni/Pd decorated at 60 min, where the maximum oxidation peak for 1 M ethanol achieved +393 mA cm compared to the porous unmodified Ni electrode at +152 mA cm and flat Ni at +55 mA cm. Chronoamperometric measurements in ethanol oxidation showed that porous electrodes were characterised by higher catalytic activity than flat electrodes. In addition, applying a thin layer of precious metal on the surface of nickel increased the recorded anode current density associated with the electrochemical oxidation process. The highest activity was recorded for porous coatings after modification in a solution containing palladium ions, obtaining a current density value of about 55 mA cm, and for a flat unmodified electrode, only 5 mA cm after 1800 s.
这项工作合成了具有高催化效率的 Ni 涂层，通过增加活性表面并修饰 Pd 作为贵金属来实现。多孔 Ni 泡沫电极通过在 Ni 基底上电沉积 Al 获得。在 900°C 的 NaCl-KCl-3.5 mol%AlF 熔融盐混合物中，以-1.9 V 的电位沉积 Al 60 分钟，这与固相中 Al-Ni 相的形成有关。通过施加-0.5 V 的电位溶解 Al 和 Al-Ni 相，从而形成多孔层。将获得的多孔材料与平面 Ni 板进行比较，以评估其在碱性溶液中对乙醇氧化的电催化性能。非 Faradaic 区域的循环伏安测量显示，Ni 泡沫的形态发展得到了改善，其活性表面积比平面 Ni 电极发达 5.5 倍。通过从稀氯化物溶液（1 mM）中在不同时间置换 Pd(II)离子的电置换过程，提高了催化活性。在循环伏安扫描中，多孔 Ni/Pd 在 60 分钟时的修饰显示出最高的催化活性，对于 1 M 乙醇，最大氧化峰达到+393 mA cm，而多孔未修饰的 Ni 电极为+152 mA cm，平面 Ni 电极为+55 mA cm。在乙醇氧化的计时电流测量中，多孔电极表现出比平面电极更高的催化活性。此外，在 Ni 表面施加一层薄薄的贵金属层会增加与电化学氧化过程相关的记录阳极电流密度。在含有钯离子的溶液中进行修饰后，多孔涂层的活性最高，记录到的电流密度值约为 55 mA cm，而未经修饰的平面电极在 1800 s 后仅为 5 mA cm。
