Facile Solid-State Synthesis of Supported PtNi and PtCo Bimetallic Nanoparticles for the Oxygen Reduction Reaction

Abstract

Proton-exchange membrane fuel cells (PEMFCs) represent an essential technology for the future decarbonization of the transportation sector. A major component of PEMFCs is the catalyst, often Pt-based alloys supported on carbon black, which are sufficiently active and stable upon long-term operation under the harsh reaction conditions implied by PEMFCs. However, the catalyst synthesis is typically laborious and challenging to upscale, employing organic solvents, surfactants, or uneconomical metal deposition routes. To solve this, we offer a mechanochemically assisted two-step solvent-less methodology to produce supported metal catalysts, particularly supported PtNi and PtCo catalysts. Accordingly, metal salts are first dispersed on the designated support by planetary ball milling. Subsequently, the mixture is reduced with hydrogen and annealed under an inert atmosphere to yield supported alloyed nanoparticles. Notably, by applying our procedure to the synthesis of carbon-supported PtNi and PtCo nanoparticles, we demonstrate that size, composition, and total metal loading can be finely adjusted, leading to highly performant catalysts in the oxygen reduction reaction (ORR).

Batch Preparation of PtCo/C for High-Performance Oxygen Reduction Reaction Based on a Continuous-Flow Microwave Pipeline Reactor

“…Due to their concave and high refractive index surfaces as well as synergistic effects between Pt and Co atoms, the PtCo CNCs exhibit significantly enhanced methanol oxidation activity and excellent electrocatalytic stability. In general, the current methods for synthesizing PtCo catalysts mainly include liquid-phase reduction, solid-phase reduction, electrochemical synthesis, and impregnation reduction. − The liquid-phase reduction method often requires the selection of a suitable surfactant for capping, yet the surfactant is generally difficult to remove. Electrochemical methods can prepare homogeneous films but are not very controllable.…”

Relevant Parameters for the Mechanochemical Synthesis of Bimetallic Supported Catalysts

“…When this method is extended to the synthesis of bimetallic supported catalysts, an additional issue caused by the metal-metal interaction comes into the play, making a systematic approach difficult but highly desirable. So far, the number of research papers on supported bimetallic (thermo) catalysts obtained by ball milling is still quite limited [12][13][14][15][16][17][18][19][20][21][22]. However, some important elements have been highlighted.…”

“…The simultaneous deposition of two metals can already be successfully obtained in short milling times and with relatively mild energy [13,19,21], but it strongly depends on the choice of the precursors and, possibly, on the support. Metal co-deposition is relatively easy with the appropriate conditions, but the formation of an alloy usually requires subsequent thermal treatments [13,20,21,23]. Interestingly, it has been found that energy-intensive thermal steps can be overcome by longer milling times [11,14,24], even if this can lead to the contamination of the catalyst by the milling media.…”

“…Crystals 2023, 13, x FOR PEER REVIEW 2 of 16 of an alloy usually requires subsequent thermal treatments [13,20,21,23]. Interestingly, it has been found that energy-intensive thermal steps can be overcome by longer milling times [11,14,24], even if this can lead to the contamination of the catalyst by the milling media.…”