Effect Of Transition Metal Nitride On Performance Of Pt Electrocatalyst For Low-temperature Fuel Cell

The widely used carbon-based support of Pt/C catalyst is not robust enough and the weak interaction between support and the metal nanoparticles resulting in a poor performance, which further results in migration, aggregation, and Ostwald ripening of Pt nanoparticles (NPs), leading to a poor durability for the long-term operations of the low-temperature fuel cells, thus designing and synthesis catalyst with high performance and durability is greatly desirable. In this work, by the combination of solvothermal alcoholysis/hydrothermal process and post-nitriding method, titanium nitride nanotubes (TiN NTs), titanium molybdenum nitride nanoparticles (Ti0.8Mo0.2N NPs), titanium cobalt nitride nanoparticles (Pt/Ti0.9Co0.1N NPs), with porous structure and high surface area, were proposed and used at a support for Pt nanoparticles. X ray diffraction (XRD), nitrogen adsorption/desorption (BET), scanning electron microscope (SEM) and transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) measurements and electrochemical test have been performed to investigate the physicochemical and catalytic properties of the synthesized catalyst.The Pt/TiN NTs catalyst exhibits high activity and stability for the oxygen reduction reaction (ORR). The accelerated durability test (ADT) reveals that the novel supporting material can dramatically enhance the durability of the catalyst and maintain the electrochemical active surface area (ECSA) of Pt, which shows great improvement in ECSA loss, with 77% of the initial ECSA remaining even after 12000 ADT cycles, much higher than the commercially Pt/C (JM) catalyst. The experimental data verified the strong metal/support interaction between Pt nanoparticles (NPs) and the TiN NTs support. The surface of the TiN NTs is composed of dendrite nanocrystals, which may function as ’hunters’ for re-capture and re-nucleation of the Pt species (atoms or clusters) which would dissolve into the electrolyte, preventing leaching and migrating of dissolved Pt NPs.XRD and TEM results of Ti0.8Mo0.2N show that the synthesized Ti0.8Mo0.2N is formed as a single-phase solid solution with high purity. Notable, Ti0.8Mo0.2N supported Pt catalyst exhibits a much higher mass activity and durability than that of the conventional Pt/C (JM) electrocatalysts for methanol electrooxidation. The experimental data indicate that the Mo doping has the bifunctional effect that improves the performance and durability of the supported Pt NPs by inducing both co-catalytic and electronic effects.Ti0.9Co0.1N with nanoscale morphology has been used as the Pt support to produce a highly active and stable electrocatalyst for the oxygen reduction reaction (ORR) under acidic conditions. XRD and TEM results show that the synthesized Ti0.9Co0.1N is formed as a single-phase solid solution with high purity. The XPS measurements verified the strong metal/support interaction between Pt nanoparticles (NPs) and the Ti0.9Co0.1N support. Notable, Ti0.9Co0.1N supported Pt catalyst (Pt/Ti0.9Co0.1N) exhibits a much higher mass activity and durability than that of the commercial JM Pt/C electrocatalysts for ORR. The accelerated durability test (ADT) reveals that the novel supporting material can dramatically enhance the durability of the catalyst and maintain the electrochemical active surface area (ECSA) of Pt, which shows great improvement in ECSA preservation, with 60% of the initial ECSA remaining even after 10000 ADT cycles, much higher than the commercial JM Pt/C catalyst. The experimental data indicate that the electronic structure of Pt can be modified by Co doping, and there exists a strong interaction between Pt and Ti0.9Co0.1N support, both of them are playing an important role in improving the activity and durability of the Pt/Ti0.9Co0.1N catalyst.