单分散有序的铟钯纳米粒子：铟的合成及其对提高乙醇氧化反应的电催化活性的作用。
Monodisperse ordered indium-palladium nanoparticles: synthesis and role of indium for boosting superior electrocatalytic activity for ethanol oxidation reaction.
机构信息
Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
出版信息
Nanoscale. 2019 Feb 14;11(7):3336-3343. doi: 10.1039/c8nr07342b.
The slow kinetics of ethanol oxidation reaction (EOR) has limited its widespread use for fuel cells. Bimetallic catalysts with optimized surface compositions can considerably govern rate-determining steps through selectivity for CH3COOH formation or by facilitating the adsorption of OHadsvia the bifunctional effect of an alloy to increase the EOR's kinetic rates. Here, we reported monodisperse ordered In-Pd nanoparticles as new bimetallic high-performance catalysts for EOR. In-Pd nanoparticles, i.e., In3Pd2 and In3Pd5 were prepared using arrested precipitation in solution, and their composition, structures, phase and crystallinity were confirmed using a variety of analyses including TEM, XPS, EDS and XRD. In-Pd nanoparticles were loaded on carbon black (Vulcan XC-72) as electrocatalysts for EOR in alkaline media. In3Pd2 and In3Pd5 nanoparticles exhibited 5.8 times and 4.0 times higher mass activities than commercial Pd/C, which showed that the presence of indium greatly boosts electrocatalytic reactivity for EOR of Pd catalysts. This performance is the best among those of bimetallic nanoparticles reported to date. Such high performance of In-Pd nanoparticles may be attributed to the following two reasons. First, In-Pd nanoparticles exhibited excellent CO anti-poison ability, as confirmed by CO striping experiments. Second, as revealed by DFT calculations of metals with OHads adsorption, In atoms on In3Pd2 surface exhibited the lowest energy (-1.659 eV) for OHads adsorption as compared to other common oxophilic metals including Sn, SnPt, Ag, Ge, Co, Pb, and Cu. We propose that the presence of indium sites promoted efficient free OH radical adsorption on indium sites and resulted in a faster reaction rate of acetate formation from acetaldehyde (the rate determining step for EOR on Pd sites). Finally, a single direct ethanol fuel cell (DEFC) with Pd/C anode was prepared. Compared to the results for a commercial Pd/C anode, the open circuit voltage (OCV) of In3Pd2/C improved by 0.25 V (from 0.64 to 0.89 V) and the power density improved by ∼80% (from 3.7 to 6.7 mW cm-2), demonstrating its practical uses as Pt or Pd catalyst alternatives for DEFC.
乙醇氧化反应（EOR）的缓慢动力学限制了其在燃料电池中的广泛应用。具有优化表面成分的双金属催化剂可以通过对 CH3COOH 形成的选择性或通过合金的双功能效应促进 OHads 的吸附来极大地控制速率决定步骤，从而提高 EOR 的动力学速率。在这里，我们报道了单分散有序的 In-Pd 纳米粒子作为新型双金属高性能 EOR 催化剂。使用溶液中的 arrested precipitation 制备了 In-Pd 纳米粒子，即 In3Pd2 和 In3Pd5，并使用各种分析方法（包括 TEM、XPS、EDS 和 XRD）确认了它们的组成、结构、相和结晶度。将 In-Pd 纳米粒子负载在 Vulcan XC-72 炭黑上作为碱性介质中 EOR 的电催化剂。In3Pd2 和 In3Pd5 纳米粒子的质量活性比商业 Pd/C 高 5.8 倍和 4.0 倍，表明铟的存在极大地提高了 Pd 催化剂对 EOR 的电催化反应性。这一性能是迄今为止报道的双金属纳米粒子中最好的。In-Pd 纳米粒子的这种高性能可能归因于以下两个原因。首先，通过 CO 剥离实验证实，In-Pd 纳米粒子表现出优异的 CO 抗中毒能力。其次，通过对具有 OHads 吸附的金属的 DFT 计算表明，与其他常见的亲氧金属（包括 Sn、SnPt、Ag、Ge、Co、Pb 和 Cu）相比，In3Pd2 表面上的 In 原子对 OHads 吸附的能量最低（-1.659 eV）。我们提出，铟位点的存在促进了自由 OH 自由基在铟位点上的有效吸附，从而导致乙醛（Pd 位点上 EOR 的速率决定步骤）形成乙酸盐的反应速率更快。最后，制备了带有 Pd/C 阳极的单乙醇直接燃料电池（DEFC）。与商用 Pd/C 阳极的结果相比，In3Pd2/C 的开路电压（OCV）提高了 0.25 V（从 0.64 到 0.89 V），功率密度提高了约 80%（从 3.7 到 6.7 mW cm-2），证明其作为 DEFC 中 Pt 或 Pd 催化剂替代品的实际用途。
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