Gas-Phase Synthesis of PtMo Alloy Electrocatalysts with Enhanced Activity and Durability for Oxygen Reduction Reaction

Abstract

The proton-exchange membrane fuel cell is a promising technology to effectively utilize hydrogen energy, which is the ideal alternative to fossil fuels. However, the high dependency on scarce Pt as an oxygen reduction reaction (ORR) electrocatalyst is still a severe barrier that hinders widespread commercialization. Herein, we propose a facile synthetic strategy facilitating mass production of Pt–Mo solid-solution alloy nanoparticles on a carbon support (PtMo/C) as a highly active ORR electrocatalyst. Without using organic surfactants or reducing agents, our synthesis process based on the gas-phase method in an inert atmosphere is cost-effective and does not require any post-treatment, unlike most reported solution-based reduction processes. Both molybdenum metal and carbon monoxide decomposed from molybdenum hexacarbonyl contribute to the reduction of the PtMo alloy during the annealing process. By elucidating the growth and synthesis mechanisms, we optimized the particle size of PtMo/C to approximately 3.1 nm, annealed at 800 °C (PtMo/C-800). Consequently, PtMo/C-800 shows high mass activity (146 mA mgPt –1), which is superior to that of commercial Pt/C, and excellent durability after accelerated degradation tests.

Local Oxidation Induced Amorphization of 1.5‐nm‐Thick Pt–Ru Nanowires Enables Superactive and CO‐Tolerant Hydrogen Oxidation in Alkaline Media

“…This annealing-induced amorphization is conflicting with conventional cognition, as a heating treatment is commonly conducive to the enhancement of crystallinity for metallic materials. [38,39] To illuminate the roots for this interesting phenomenon, we also implemented the synthetic procedure on carbon-loaded pure Pt NWs and bimetallic Pt-Ru NWs with other atomic ratios, i.e., Pt 73 Ru 27 and Pt 88 Ru 12 NWs (Figures S3-S5, Table S1, Supporting Information), respectively. After 200 °C annealing in air, we find this crystalline-to-amorphous transformation also occurred on Pt 73 Ru 27 and Pt 88 Ru 12 NWs as all the XRD diffraction peaks vanished (Figure S5, Supporting Information), while pure Pt NWs inversely exhibited an enhanced crystallinity (Figure S6, Supporting Information).…”

Understanding the Metal Carbonyl-Assisted Synthesis of PtMoCu/C Nanocatalysts for Proton-Exchange Membrane Fuel Cells

“…To understand the difference in durability, we examined the catalysts after the ADTs by TEM (Figure S8). Most of the particles in the PtMoCu-SCR/C and benchmark Pt/C became severely aggregated after 10,000 cycles, whereas the PtMoCu/C and PtMo/C still maintained their initial shape, and no obvious aggregation was observed, which is possibly due to the sacrificial oxidation of Mo to protect the Pt oxidation. , Furthermore, we evaluated the atomic ratios of Pt, Cu, and Mo in the benchmark Pt/C, PtMo/C, PtMoCu/C, and PtMoCu-SRC/C before and after the ADT tests by analyzing the ICP–MS (Table S2). There were no significant compositional changes in all samples.…”

“…Furthermore, it improves the electrocatalytic ORR activity and stability by changing the electronic structure and lattice parameters of Pt. , Among the various non-noble metals, Cu exhibits excellent durability with respect to electrochemical oxidation in acidic environments . Meanwhile, group 6 metals, such as Mo or W, can alleviate the reduction of ligand as well as the strain effect by stabilizing Pt and metal elements against dissolution on the catalyst surface in acidic environments. − Thus, using trimetallic PtMoCu or PtWCu is an effective strategy to reduce the utilization of Pt and stabilize it against its dissolution in an acidic solution.…”

Electrochemical trends of a hybrid platinum and metal–nitrogen–carbon catalyst library for the oxygen reduction reaction

“…0.3 V to 0.8 V), which was not observed in the Mo-N-C sample (without Pt nanoparticles), but has been previously observed in Pt-Mo catalysts and attributed to redox transitions of the Mo from the Mo 4+ to Mo 6+ state, further evidencing a change in the chemical nature of the Pt nanoparticles due to interactions with the Mo-N x sites. [35][36][37][38]…”