Center for Advanced Materials, Qatar University, Doha 2713, Qatar.
Gas Processing Center (GPC), College of Engineering, Qatar University, Doha 2713, Qatar.
Int J Mol Sci. 2023 Jul 23;24(14):11832. doi: 10.3390/ijms241411832.
Tailoring the shape of Pd nanocrystals is one of the main ways to enhance catalytic activity; however, the effect of shapes and electrolyte pH on carbon monoxide oxidation (CO) is not highlighted enough. This article presents the controlled fabrication of Pd nanocrystals in different morphologies, including Pd nanosponge via the ice-cooling reduction of the Pd precursor using NaBH solution and Pd nanocube via ascorbic acid reduction at 25 °C. Both Pd nanosponge and Pd nanocube are self-standing and have a high surface area, uniform distribution, and clean surface. The electrocatalytic CO oxidation activity and durability of the Pd nanocube were significantly superior to those of Pd nanosponge and commercial Pd/C in only acidic (HSO) medium and the best among the three media, due to the multiple adsorption active sites, uniform distribution, and high surface area of the nanocube structure. However, Pd nanosponge had enhanced CO activity and stability in both alkaline (KOH) and neutral (NaHCO) electrolytes than Pd nanocube and Pd/C, attributable to its low Pd-Pd interatomic distance and cleaner surface. The self-standing Pd nanosponge and Pd nanocube were more active than Pd/C in all electrolytes. Mainly, the CO current density of Pd nanocube in HSO (5.92 mA/cm) was nearly 3.6 times that in KOH (1.63 mA/cm) and 10.3 times that in NaHCO (0.578 mA/cm), owing to the greater charge mobility and better electrolyte-electrode interaction, as evidenced by electrochemical impedance spectroscopy (EIS) analysis. Notably, this study confirmed that acidic electrolytes and Pd nanocube are highly preferred for promoting CO and may open new avenues for precluding CO poisoning in alcohol-based fuel cells.
调控钯纳米晶的形貌是提高其催化活性的主要方法之一，但形貌和电解质 pH 对一氧化碳氧化（CO）的影响还没有得到足够的重视。本文通过使用 NaBH 溶液冰冷却还原 Pd 前体，制备了具有不同形貌的 Pd 纳米晶，包括 Pd 纳米海绵，以及在 25°C 下使用抗坏血酸还原制备的 Pd 纳米立方体。Pd 纳米海绵和 Pd 纳米立方体均为自支撑结构，具有高比表面积、均匀的分布和清洁的表面。在仅酸性（HSO）介质中，Pd 纳米立方体的电催化 CO 氧化活性和耐久性明显优于 Pd 纳米海绵和商业 Pd/C，这归因于纳米立方体结构的多吸附活性位、均匀的分布和高比表面积。然而，在碱性（KOH）和中性（NaHCO）电解质中，Pd 纳米海绵比 Pd 纳米立方体和 Pd/C 具有更高的 CO 活性和稳定性，这归因于其较低的 Pd-Pd 原子间距离和更清洁的表面。自支撑的 Pd 纳米海绵和 Pd 纳米立方体在所有电解质中的活性均高于 Pd/C。主要原因是，在 HSO 中，Pd 纳米立方体的 CO 电流密度（5.92 mA/cm）接近在 KOH 中的 3.6 倍（1.63 mA/cm）和在 NaHCO 中的 10.3 倍（0.578 mA/cm），这是由于电荷迁移率更高和电解质-电极相互作用更好，这可以通过电化学阻抗谱（EIS）分析得到证实。值得注意的是，本研究证实了酸性电解质和 Pd 纳米立方体更有利于促进 CO 的氧化，这可能为防止醇基燃料电池中的 CO 中毒开辟新途径。
