多孔氮化钛载体上铂催化剂的原子层沉积制备及其催化氧气还原性能

为有效解决铂(Pt)催化剂用于氧气还原反应(ORR)面临的催化活性及稳定性问题,本文首先合成了具有良好导电性、电化学稳定以及耐腐蚀等优点的一维多孔氮化钛(Ti N)纳米管载体材料,然后使用原子层沉积技术(ALD)在Ti N载体上沉积制备了Pt催化剂(ALD-Pt/Ti N),所得的Pt纳米颗粒尺寸均匀、高度分散且与Ti N载体之间存在着较强的相互作用。催化氧气还原活性和稳定性测试表明,所得的ALD-Pt/Ti N对ORR具有较高的催化活性,同时兼具良好的稳定性和耐久性。相比商用Pt/C,ALD-Pt/Ti N的起始电位和稳态极限电流密度与其相近,半波电位则高出了20 m V,表现出优异的电催化性能。其优良的电催化性能主要归因于ALD沉积Pt纳米颗粒的高分散性,一维多孔结构Ti N载体的高比表面积、良好导电性和抗腐蚀性能以及ALD-Pt与Ti N载体间较强的相互作用等综合影响。本工作为设计新型高催化活性、高稳定性的Pt基催化剂提供了有益借鉴。

Preparation of Platinum Catalysts on Porous Titanium Nitride Supports by Atomic Layer Deposition and Their Catalytic Performance for Oxygen Reduction Reaction

The exploitation of high-performing stable oxygen reduction reaction (ORR) electrocatalysts is critical for energy storage and conversion technologies. The existing high-efficiency electrocatalysts applied to the ORR are mainly based on Pt and its alloys. Moreover, carrier catalysts are the most widely used in actual electrocatalysis. A suitable carrier not only improves the utilization rate of precious metals and the service life of the catalyst, but also serves as a co-catalyst to ameliorate the catalytic activity through a synergistic effect in the reaction. Therefore, research into Pt-based electrocatalysts mainly focuses on the precious metal Pt and the carrier. With the aim of improving the activity and durability of Pt-based catalysts for the ORR, one-dimensional porous titanium nitride (TiN) nanotubes with a large specific surface area as well as good conductivity, electrochemical stability, and corrosion resistance were prepared in this study, and then, Pt nanoparticles were deposited on the TiN-support by atomic layer deposition (ALD). ALD is a novel and simple method for the preparation of films or nanoparticles with fine control of the thickness or size, respectively. The results of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) experiments confirmed that the Pt nanoparticles obtained by ALD (ALD-Pt/TiN) were face-centered cubic (fcc) crystals with a uniform size and were highly dispersed on the surface of TiN. X-ray spectroscopy (XPS) measurements verified that the binding energy of Pt 4f in ALD-Pt/TiN was positively shifted by 0.33 eV with respect to that of the Pt/C catalyst, indicating strong electronic interactions between the ALD-Pt nanoparticles and the TiN carriers. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) analyses revealed that ALD-Pt/TiN possessed high activity for the ORR and favorable durability. The onset potential and diffusion-limiting current density of ALD-Pt/TiN were similar to those of commercial Pt/C, while the half-wave potential was 20 mV higher than that of commercial Pt/C, indicating better electrocatalytic performance of the designed material. Furthermore, the electrocatalytic mechanism and kinetics for ALD-Pt/TiN were investigated by rotating ring-disc electrode (RRDE) experiments. The results suggested that the electron transfer number of the ALD-Pt/TiN catalyst was about 3.93, indicating that the ORR on the electrode was dominated by an efficient four-electron pathway. At the same time, the peroxide content was only 5%. The results of accelerated durability testing (ADT) showed that ALD-Pt/TiN had better ORR stability than Pt/C. This excellent electrocatalytic performance was probably due to the high dispersibility of the Pt nanoparticles deposited by ALD, good conductivity and corrosion resistance of TiN, and strong interactions between ALD-Pt and the TiN support. This work provides a reliable strategy for the design of new electrocatalytic materials with high activity and stability. Future research will focus on the strong interactions between ALD-Pt and the TiN carriers.