Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Nanoscale. 2017 Jan 19;9(3):1154-1165. doi: 10.1039/c6nr08359e.
For the first time, shape-tunable Pt-Ir alloy nanocatalysts including both single-crystalline (nano-octahedra (NOs), nano-truncated octahedra (NTOs), nanocubes (NCs)) and polycrystalline (nanocluster flowers (NCFs), nanowires (NWs), nano-short-chains (NSCs), and nano-octahedral stars (NOSs)) ones were synthesized with a facile one-pot solvothermal method, via precise control of the facet-selective agents (Br and I). The surface effects of Pt-Ir alloy nanocatalysts for oxygen electrode reaction in acidic solution were intensively investigated. Pt-Ir alloy nanocatalysts showed enhanced catalytic activities for the oxygen evolution reaction (OER), which were 1.6 to 2.0 times those of the commercial Ir/C catalyst and the Pt/C-Ir/C mixture at an overpotential of 0.25 V. The catalytic activity for the OER exhibited a positive correlation with the proportion of surface IrO species, but was restricted by the surface alloying effect. Besides the change of the intermediate adsorption state, the dissociation of water was also confirmed to be effective as the rate-determining step of the Pt-Ir alloy nanocatalysts. The catalytic activity for the oxygen reduction reaction (ORR) decreased with the increase of surface IrO species. Pt-Ir nano-short-chains (NSCs) exhibited 1.3 times the catalytic activity as that of the commercial Pt/C catalyst at 0.80 V and 0.85 V, owing to the higher proportion of the (110) facets with irregular step sites exposed after the annealing treatment at 350 °C. The unique structure could prevent the mass transfer process from being obstructed by adsorbed bisulfate anions and oxidized species on the surfaces. Pt-Ir NSCs exhibited a catalytic efficiency of 46.7% and were considered to be a promising URFC catalyst.
首次采用简便的一锅溶剂热法，通过精确控制面选择性试剂（Br 和 I），合成了具有可调形状的 Pt-Ir 合金纳米催化剂，包括单晶（纳米八面体（NOs）、纳米截断八面体（NTOs）、纳米立方体（NCs））和多晶（纳米团簇花（NCFs）、纳米线（NWs）、纳米短链（NSCs）和纳米八面体星（NOSs））。在酸性溶液中，研究了 Pt-Ir 合金纳米催化剂对氧电极反应的表面效应。Pt-Ir 合金纳米催化剂对析氧反应（OER）表现出增强的催化活性，在 0.25 V 的过电势下，其活性是商业 Ir/C 催化剂和 Pt/C-Ir/C 混合物的 1.6 至 2.0 倍。OER 的催化活性与表面 IrO 物种的比例呈正相关，但受到表面合金化效应的限制。除了中间吸附态的变化外，还证实水的解离也是 Pt-Ir 合金纳米催化剂的速率决定步骤。析氧反应（ORR）的催化活性随表面 IrO 物种的增加而降低。Pt-Ir 纳米短链（NSCs）在 0.80 V 和 0.85 V 下的催化活性是商业 Pt/C 催化剂的 1.3 倍，这归因于在 350°C 退火处理后暴露的具有不规则台阶的（110）面的比例更高。独特的结构可以防止传质过程被吸附的硫酸根阴离子和表面上的氧化物种所阻碍。Pt-Ir NSCs 表现出 46.7%的催化效率，被认为是一种很有前途的 URFC 催化剂。
