Cobalt‐Doping Stabilized Active and Durable Sub‐2 nm Pt Nanoclusters for Low‐Pt‐Loading PEMFC Cathode

Abstract

Proton exchange membrane fuel cells (PEMFCs) suffer severe performance loss in the high current density (HCD) region as Pt‐loading decreases. A smaller electrocatalyst size inducing a higher electrochemically active surface area (ECSA) is critical for solving this issue. However, the poor electrocatalytic activity and stability of sub‐2 nm nanoclusters limit the potential to reduce their size. In this study, 1.69 nm Co‐doped Pt nanoclusters with a large ECSA (116.19 m2 gPt–1) are synthesized. The mass activity (MA) (0.579 A mgPt–1) and stability (9% MA loss after 30k potential cycling) refresh the record of sub‐2 nm nanoclusters. The structural characterization and theoretical calculations reveal that doping reduces the total energy required to stabilize the nanoclusters. Dopant tailoring of the d‐band center and vacancy formation energy account for the activity and stability enhancement, respectively. Due to the larger ECSA and MA induced by doping, HCD voltage loss due to lower Pt‐loading is significantly reduced compared with commercial Pt/C. The peak power density of low‐Pt‐loading PEMFCs (0.075 mgPt cmMEA–2) with a doped nanocluster cathode is 0.811 W cm–2 (H2–air condition), which far exceeds commercial Pt/C (0.5 W cm–2) and that of most reported electrocatalysts.

Coating Porous TiO2 Films on Carbon Nanotubes to Enhance the Durability of Ultrafine PtCo/CNT Nanocatalysts for the Oxygen Reduction Reaction

“…The particle sizes of PtCo/TiO 2 /CNT and PtCo/CNT (Figure a,b) were significantly reduced to 1.99 and 2.44 nm, respectively, due to Co doping, which was consistent with the XRD results. Trace Co atoms were majorly present at the skin of NPs, which facilitated the formation of stable ultrafine NPs, as verified by density functional theory calculations . In addition, the particle distribution of PtCo/TiO 2 /CNT was more uniform than that of PtCo/CNT with little agglomeration (Figure c), resulting in smaller particles and indicating that the presence of TiO 2 facilitated the dispersion of PtCo NPs.…”

“…Trace Co atoms were majorly present at the skin of NPs, which facilitated the formation of stable ultrafine NPs, as verified by density functional theory calculations. 20 In addition, the particle distribution of PtCo/TiO 2 /CNT was more uniform than that of PtCo/CNT with little agglomeration (Figure 3c), resulting in smaller particles and indicating that the presence of TiO 2 facilitated the dispersion of PtCo NPs. The high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) results and the corresponding elemental mapping images confirmed the consistent distribution of the various elements, especially Pt and Ti, throughout the structure (Figure 3d−i).…”

“…The 0.352 nm lattice stripe is correlated with the TiO 2 (101) crystal face, and the 0.229 nm lattice stripe is correlated with the Pt (111) crystal face, where the particle size reduction leads to lattice stretching. 20,21 It is clear that the PtCo NPs (green) and TiO 2 (yellow) are adjacent on the CNTs, which indicates that PtCo NPs are commonly present at the location where the TiO 2 is in contact with the CNT phase. 22 We confirmed this inference by performing elemental line sweeps on the catalyst in different directions (Figure 4b Furthermore, XPS was used to study the electronic structure differences between PtCo/TiO 2 /CNT and the other samples.…”

Low-Loading Sub-3 nm PtCo Nanoparticles Supported on Co–N–C with Dual Effect for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

“…21 However, Pt-alloy intermetallic compounds prepared by traditional methods showed a large particle size (around 5−10 nm), 33,40,41 which would reduce the Pt utilization and increase the oxygen mass transport resistance. 42 Besides, the separate method of synthesizing alloy nanoparticles and then loading them on M−N−C carriers resulted in weaker metal−support interaction and uncontrollable particle size. 15 Meanwhile, the metal−support interaction would be weakened with the increase of alloy nanoparticle size, 43,44 which caused a poor performance for catalysts.…”

Iron- and Cobalt-Doped Palladium/Carbon Nanoparticles as Catalysts for Formic Acid Oxidation

“…In addition, doping has also received a lot of attention from scientists in recent years . Relevant studies show that the electronic structure and composition of catalysts can be effectively tuned by doping other elements (H, B, P, S, Cr, Ga, Rh, Fe, and Co), greatly improving the catalytic efficiency of the catalysts. − In the catalytic reaction, the amount of doping metal greatly affects its catalytic efficiency . Usually, the optimum catalytic efficiency corresponds to the optimum composition of the catalyst .…”