Strong Coupling Effects between Single Metal Site-Rich Carbon and PtCo Intermetallic Catalysts for Heavy-Duty Meas

Abstract

Developing active and durable low-platinum group metal (PGM) oxygen reduction reaction (ORR) catalysts for proton-exchange membrane fuel cells (PEMFCs) remains a critical challenge for heavy-duty vehicle (HDV) applications. This work comprehensively studies synergistic catalysts, composed of Pt-based nanoparticles and supports with atomically dispersed M-N-C sites (MnSA-NC), using a suite of experimental techniques and DFT calculations. DFT calculations predicted that the presence of Mn-N4 sites could induce a strong coupling effect between Pt and support, which can strongly bind with Pt to immobilize the Pt clusters and weaken the adsorption of oxygen on the Pt surface to enhance intrinsic activity. In addition to the favorable MnN4 dopants, the MnSA-NC support is optimal support with sufficient surface areas, porosities, and adequate graphitization degree. Subsequently, well-dispersed Pt and ordered L12-Pt3Co nanoparticles with an average diameter of 2.1 nm and 3.3 nm were deposited on the MnSA-N-C support, which was comprehensively studied as the ORR cathode catalyst for PEMFCs, presenting remarkable performance and durability. In particular, the Pt@MnSA-NC catalyst achieved a mass activity (MA) of 0.70 A mgPt −1 at 0.9 V iR -free and maintained 86 % of its initial performance after a 30,000-cycle accelerated stress test (AST). The L12-Pt3Co@MnSA-NC catalyst achieved much higher performance, with MA of 0.91 A mgPt −1 and current density of 1.63 A cm−2 at 0.7 V in an H2-air fuel cell at 150 kPaabs with 0.10 mgPt cm−2 on the cathode. Furthermore, under HDV operating conditions (250 kPaabs and 0.20 mgPt cm-2), the L12-Pt3Co@MnSA-NC catalyst delivered an impressive current density of 1.80 A cm−2 at 0.7 V, with only 13 % performance loss after the 30,000 cycles AST, showing great potential to meet the DOE target set for HDVs.