Ternary PtIrNi Catalysts for Efficient Electrochemical Ammonia Oxidation
Ternary PtIrNi Catalysts for Efficient Electrochemical Ammonia Oxidation
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DOI：
10.1021/acscatal.9b04670
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发表时间：
2020-04-03
期刊：
影响因子：
12.9
通讯作者：
Wu, Gang
中科院分区：
文献类型：
--
作者：
Li, Yi;Li, Xing;Wu, Gang
氨（NH3）通过其直接氨氧化反应（AOR）已被证明是低温燃料电池中氢的有效替代物。然而，动力学缓慢的AOR严重阻碍了直接氨燃料电池（DAFC）的应用。在这里，我们报告了一个有效的AOR催化剂，其中三元PtIrNi合金纳米粒子分散在由多孔二氧化硅（SiO2）和羧基功能化的碳纳米管（PtIrNi/SiO2-CNT-COOH）组成的二元复合载体通过声化学辅助合成方法。PtIrNi合金纳米颗粒在碱性介质中，由于多孔SiO2提供了丰富的OHad，而CNTs提高了其导电性，因此表现出了显著的AOR催化活性。其通过在室温下比商业PtIr/C（约0.5V）更低的起始电势（类似于0.40V vs可逆氢电极（RHE））来证明。0.43 V与RHE）。增加NH3浓度和操作温度可以显着增强该PtIrNi纳米颗粒催化剂的AOR活性。具体地，在80 ° C的温度下的催化剂表现出低得多的起始电位（类似于0.32V vs RHE）和较高的峰值电流密度，表明在较高温度下操作的DAFC有利于提高性能。恒势密度泛函理论（DFT）计算表明，Pt-Ir系综位于{100}-末端表面上，是活性中心.与Pt和Pt 3 Ir合金相比，Ni的引入提高了投射到表面位d族轨道上的态密度中心能，从而降低了 * NH 2脱氢为 *NH的理论起始势。
Ammonia (NH3) has proved to be an effective alternative to hydrogen in low-temperature fuel cells via its direct ammonia oxidation reaction (AOR). However, the kinetically sluggish AOR has prohibitively hindered the attractive direct ammonia fuel cell (DAFC) applications. Here, we report an efficient AOR catalyst, in which ternary PtIrNi alloy nanoparticles well dispersed on a binary composite support consisting of porous silicon dioxide (SiO2) and carboxyl-functionalized carbon nanotube (PtIrNi/SiO2-CNT-COOH) through a sonochemical-assisted synthesis method. The PtIrNi alloy nanoparticles, with the aid of abundant OHad provided by porous SiO2 and the improved electrical conductivity by CNTs, exhibit remarkable catalytic activity for the AOR in alkaline media. It is evidenced by a lower onset potential (similar to 0.40 V vs reversible hydrogen electrode (RHE)) at room temperature than that of commercial PtIr/C (ca. 0.43 V vs RHE). Increasing NH3 concentrations and operation temperatures can significantly enhance AOR activity of this PtIrNi nanoparticle catalyst. Specifically, the catalyst at the temperature of 80 degrees C exhibits a much lower onset potential (similar to 0.32 V vs RHE) and a higher peak current density, indicating that DAFCs operated at a higher temperature are favorable for increased performance. Constant-potential density functional theory (DFT) calculations showed that the Pt-Ir ensembles on {100}-terminated surfaces serve as the active site. The introduction of Ni raises the center energy of the density of states projected onto the group d-orbitals of surface sites and thus lowers the theoretical onset potential for *NH2 dehydrogenation to *NH compared to Pt and Pt3Ir alloy.