Department of Chemistry, Beijing Key Laboratory for Microanalytical Methods and Instrumentation, Tsinghua University, Beijing 100084 (PR China).
ChemSusChem. 2013 Oct;6(10):2016-21. doi: 10.1002/cssc.201300331. Epub 2013 Aug 22.
The high price of platinum (Pt)-based cathode catalysts for the oxygen reduction reaction (ORR) have slowed down the practical application of fuel cells. Thanks to their low cost, and outstanding, stable catalytic properties, titanium nitrides (TiN) are among the most promising non-precious metal electrocatalysts for replacing Pt. However, the shape-activity relationships of TiN electrocatalysts have not been well-studied or understood up to now. In this work, by simply adjusting the shape of TiO2 precursor, we are able to tailor the morphology of the TiN catalysts from nanoparticles to nanotubes. We have synthetized uniform carbon-coated titanium nitride nanotubes (carbon-coated TiN NTs) through a nitridation reaction in NH3 flow using a TiO2 nanotubes/melamine mixture as precursor. The carbon-coated TiN NTs hybrids exhibit excellent electrocatalytic activity for the ORR, coupled with superior methanol tolerance and long-term stability in comparison to commercial Pt/C, through an efficient four-electron-dominant ORR process. Compared with nanoparticles, the one-dimensional and hollow structure of the nanotubes result in greater diffusion of electrolyte and superior electrical conductivity, and contribute to the greatly improved electrocatalytic performance of the carbon-coated TiN NTs nanocomposites.
对于氧还原反应（ORR）而言，铂（Pt）基阴极催化剂价格高昂，这极大地限制了燃料电池的实际应用。由于成本低廉且具有出色、稳定的催化性能，氮化钛（TiN）是最有前途的非贵金属电催化剂之一，有望替代 Pt。然而，TiN 电催化剂的形状-活性关系至今仍未得到很好的研究或理解。在这项工作中，我们通过简单地调整 TiO2 前体的形状，能够将 TiN 催化剂的形貌从纳米颗粒调至纳米管。我们使用 TiO2 纳米管/三聚氰胺混合物作为前驱体，在 NH3 流中通过氮化反应合成了均匀的碳包覆氮化钛纳米管（碳包覆 TiN NTs）。与商业 Pt/C 相比，碳包覆 TiN NTs 杂化物通过高效的四电子主导 ORR 过程，表现出优异的 ORR 电催化活性，同时具有出色的甲醇耐受性和长期稳定性。与纳米颗粒相比，纳米管的一维和中空结构促进了电解质的更好扩散和更高的导电性，有助于极大地提高碳包覆 TiN NTs 纳米复合材料的电催化性能。
