H-Y Lee, C-H Shin, T.H. Yu, W.A. Goddard III, J-S Yu
Keywords: new highly graphitized carbon support, n-doping, oxygen reduction reaction, Pt fuel cell catalyst, network-structured porosity
Summary:For polymer electrolyte membrane fuel cells (PEMFCs), the state-of-the-art electrocatalysts are based on carbon-supported Pt group metals. However, current carbon supports suffer from carbon corrosion during repeated start-stop operations, causing performance degradation. We report a new strategy to produce highly graphitized porous carbon with controllable N-doping that uses low-temperature synthesis (650 ℃) from g-C3N4 carbon-nitrogen precursor with pyrolysis using Mg. The high graphiticity is confirmed by high-intensity 2D Raman peak with low ID/IG (0.57), pronounced graphitic XRD planes, and excellent conductivity. Without further post-treatment, this highly graphitized N-doped porous carbon (GNPC) material combines high pyrrolic-N content with high porosity. Supporting Pt on GNPC exhibits excellent oxygen reduction activity for PEMFC with greatly improved durability as proved by real-time loss measurements of Pt and carbon, the first to surpass the DOE 2025 durability targets for both catalyst and support. The Pt/GNPC prepared at 650 oC shows 32 and 24% drop in mass activity after accelerated durability tests of both electrocatalyst and support, respectively, which are less than DOE target of 40% loss. The atomistic basis for this durability is explained via quantum mechanics-based molecular dynamics simulations. Interestingly, it is found that pyrrolic-N strongly interacts with Pt, making the Pt catalyst more stable during fuel cell reaction. We expect that high porosity robust graphitized materials will lead to many other novel applications for electrocatalysis with durable carbon frameworks.