Armoring the Pt/C Catalyst with Fine Atomic-Scale Tungsten Species to Increase Tolerance against Thermal and Fuel Cell Stresses

Abstract

An atomic-scale tungsten (ASW)-armored carbonsupported catalyst is prepared by applying ultrafine tungsten species dispersed onto the surface of a commercially available Pt/C catalyst. Tungsten-chloro-methoxide has proven to be a useful molecular precursor that allows for the uniform deposition of ASW on the carbon support and at the periphery of the Pt nanoparticles. ASW imparts exceptional thermal stability as evidenced by the minimal sintering of nanoparticulate species at an elevated temperature of 700 °C. Moreover, when employed as an oxygen reduction reaction catalyst, the ASW-armored catalyst exhibits improved activity and impressive durability. With 1.6 times higher initial mass activity, the ASW-armored catalyst only showed a 6.5 mV loss of half wave potential compared to 16 mV for pristine Pt/ C after 30,000 cycles of the accelerated stress test (AST). Cyclic voltammetry and post-mortem materials characterizations show the ASW species substantially alleviated the corrosion of carbon during AST, which caused serious oxygen transport loss observed for pristine Pt/C. Density functional theory calculation supports our hypothesis of which ASW can indeed improve the stability of carbon surface defects when a single-atom tungsten is present in close proximity. This work demonstrates the design of atomic-scale metal species for increasing the robustness of functional nanomaterials under harsh thermal and electrochemical working environments.