Titanium carbonitrides have promising catalytic properties for oxygen reduction reaction (ORR). However, its synthesis normally requires high temperatures (1200–1800 °C), thus limiting research carried-out on them. The catalytic properties of the carbonitrides have so far been improved through post-synthesis partial surface oxidation. This makes the entire process of making the desired catalyst cumbersome and complex. In this work, cobalt-modified single-walled titanium carbonitride nanotube (Co@TiC_0.25N_0.75) is synthesized via solvothermal method followed by solid-solid separation process. The problem of high temperature required for TiCN synthesis is successfully overcome, and a Co doping strategy is used to improve its catalytic performance. Different mass ratios of Co nanoparticles are loaded onto TiC_0.25N_0.75. It discovers that only a fraction of the Co dissolves at TiC_0.25N_0.75 lattice due to the solubility limit being ~ 0.98%. The remaining fraction of Co is found at the wall of the TiC_0.25N_0.75. The Co nanoparticles at the TiC_0.25N_0.75 wall complement the catalytic activity, while the dissolved Co at its lattice acts as active site modifier by increasing the proportion of Ti 2p_3/2 in the low valence state. In alkaline solution, 10%Co@TiC_0.25N_0.75 shows appreciable ORR activity with onset and half-wave potential located at 0.85 and 0.73 V respectively; the performance is higher than that of TiN (0.69 and 0.55 V) and single-phase TiC_0.25N_0.75 (0.74 and 0.62 V). The results indicate that a charge transfer occurred between Co and TiC_0.25N_0.75 due to strong coupling effect. This gives a catalyst with appreciable ORR activity and stability.

Textural Abstract

High temperature, a problem associated with titanium carbonitride synthesis, is overcome through solid-solid separation method, and Co doping strategy is used to improve its catalytic performance. During ORR activity in alkaline solution, Co@TiC_0.25N_0.75 gives appreciable current density of ~ 4.9 mA cm⁻². Onset and half-wave potential are found to be 0.85 and 0.73 V vs RHE respectively.

碳氮化钛对氧还原反应（ORR）具有良好的催化性能。但是，其合成通常需要高温（1200–1800°C），因此限制了对其进行的研究。迄今为止，碳氮化物的催化性能已经通过合成后部分表面氧化得到改善。这使得制造所需催化剂的整个过程既麻烦又复杂。在这项工作中，钴改性的单壁碳氮化钛纳米管（Co @ TiC _0.25 N _0.75通过溶剂热法然后固-固分离过程合成）。TiCN合成所需的高温问题已成功克服，并采用Co掺杂策略来提高其催化性能。将不同质量比的Co纳米颗粒负载到TiC _0.25 N _0.75上。发现由于溶解度极限为〜0.98％，只有一部分Co在TiC _0.25 N _0.75晶格中溶解。Co的剩余部分位于TiC _0.25 N _0.75的壁上。TiC _0.25 N _0.75时的Co纳米粒子壁补充了催化活性，而溶解的钴在其晶格上通过增加低价态的Ti 2p _3/2的比例充当了活性位点改性剂。在碱性溶液中，10％Co @ TiC _0.25 N _0.75表现出明显的ORR活性，起始和半波电势分别位于0.85和0.73V。性能高于TiN（0.69和0.55 V）和单相TiC _0.25 N _0.75（0.74和0.62 V）。结果表明，由于强耦合效应，在Co和TiC _0.25 N _0.75之间发生了电荷转移。这样得到的催化剂具有显着的ORR活性和稳定性。

质地摘要

通过固-固分离方法克服了高温（碳氮化钛合成相关的问题），并采用了Co掺杂策略来提高其催化性能。在碱性溶液中进行ORR活性期间，Co @ TiC _0.25 N _0.75给出的电流密度约为4.9 mA cm ^-2。相对于RHE，起始和半波电势分别为0.85 V和0.73V。