Platinum Nanocatalysts Supported on Defective Hollow Carbon Spheres: Oxygen Reduction Reaction Durability Studies

Abstract

The durability and long-term applicability of catalysts are critical parameters for the commercialization and adoption of fuel cells. Even though a few studies have been conducted on hollow carbon spheres (HCSs) as supports for Pt in oxygen reduction reactions (ORR) catalysis, in-depth durability studies have not been conducted thus far. In this study, Pt/HCSs and Pt/nitrogen-doped HCSs (Pt/NHCSs) were prepared using a reflux deposition technique. Small Pt particles were formed with deposition on the outside of the shell and inside the pores of the shell. The new catalysts demonstrated high activity (>380 μA cm−2 and 240 mA g−1) surpassing the commercial Pt/C by more than 10%. The catalysts demonstrated excellent durability compared to a commercial Pt/C in load cycling, experiencing less than 50% changes in the mass-specific activity (MA) and surface area-specific activity (SA). In stop-start durability cycling, the new materials demonstrated high stability with more than 50% retention of electrochemical active surface areas (ECSAs). The results can be rationalised by the high BET surface areas coupled with an array of meso and micropores that led to Pt confinement. Further, pair distribution function (PDF) analysis of the catalysts confirmed that the nitrogen and oxygen functional groups, as well as the shell curvature/roughness provided defects and nucleation sites for the deposition of the small Pt nanoparticles. The balance between graphitic and diamond-like carbon was critical for the electronic conductivity and to provide strong Pt-support anchoring.

Tunable Electrochemical Hydrogen Uptake and Release of Nitrogen-Doped Reduced Graphene Oxide Nanosheets Decorated with Pd Nanoparticles

“…Size determination is more accurately determined by G ( r ) analysis as both Bragg diffraction and diffuse scattering are considered. As a result, size determination is more accurate as compared to common methodologies such as Bragg diffraction and transmission electron microscopy images, which can underrepresent smaller-sized particles . In order to obtain the accurate size determination, the instrument broadening factors were first determined through G ( r ) modeling of a Sigma-Aldrich powdered diamond sample.…”

“…As a result, size determination is more accurate as compared to common methodologies such as Bragg diffraction and transmission electron microscopy images, which can underrepresent smaller-sized particles. 56 In order to obtain the accurate size determination, the instrument broadening factors were first determined through G(r) modeling of a Sigma-Aldrich powdered diamond sample. The decay of the G(r) envelope introduced by the spherical nanoparticle correction factor is highly correlated with the instrumental broadening factors.…”

Catalyst Design: Counter Anion Effect on Ni Nanocatalysts Anchored on Hollow Carbon Spheres

“…Many of these allotropes are known to possess useful properties such as high surface areas, thermal stability, chemical stability under harsh conditions, and excellent electronic conductivity [ 1 , 2 , 3 ]. Owing to such attractive properties, many carbon allotropes have been explored as popular candidates in electrocatalysis as metal catalyst supports [ 4 , 5 ] as their physicochemical and/or electronic properties facilitate good dispersion of metal nanoparticles, resulting in improved catalytic performance and stability.…”

Porous spinel-type transition metal oxide nanostructures as emergent electrocatalysts for oxygen reduction reactions

“…To date, precious metals, like platinum (Pt) and palladium (Pd), remain the most excellent catalysts for ORRs, but the rarity, intolerable cost, and insufficient long-term stability of Pt are crucial barriers. [5][6][7][8][9][10][11][12][13][14] Noble-metal-free electrocatalysts, like carbon nanomaterials and single-atom materials, are promising for enhanced ORRs. [15][16][17][18][19][20] Unlike precious metals, spinel-type transition metal oxide (TMO) nanocatalysts with stoichiometric or non-stoichiometric compositions are highly promising for ORRs due to their unique physicochemical merits (i.e., rich active sites, p-type conductivity, optical transparency, magnetic properties, semiconductivity, multiple valence states of their oxides, and redox properties).…”