The Synergy of Tensile Strain and Ligand Effect in PtBi Nanorings for Boosting Electrocatalytic Alcohol Oxidation

Abstract

As the best electrocatalysts for alcohol oxidation reactions in direct alcohol fuel cells (DAFCs), Pt-based nanomaterials still face the challenges of low utilization efficiency of Pt atoms and poor reaction kinetics. To address these issues, a self-etching strategy is developed to prepare PtBi nanorings (NRs) with abundant low-coordinated atoms and inhomogeneous tensile strain (≈4%). The obtained PtBi NRs exhibit superior activity toward methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) in alkaline media. Particularly, the mass activities of PtBi NRs for MOR and EOR are 9.4 and 8.5 times higher than those of commercial Pt/C, respectively, which are among the best in the reported Pt-based catalysts. The highly open structure of PtBi NRs is believed to provide plentiful catalytic active sites and increase the utilization of Pt atoms. Theoretical calculations show that the two important factors, i.e., adsorption energy with the key reaction intermediates and the energy barrier for the potential-determining step, are significantly optimized owing to the synergy of tensile strain and the ligand effect in PtBi NRs. This study offers a promising strategy for the rational design and preparation of highly efficient catalysts for DAFCs.

Controllable Construction of PtBi Nanostructures for Enhanced Ethanol Oxidation in Acidic Media

“…As shown in Figure b, all Pt 4 f orbitals in the Pt x Bi y nanostructures showed metallic states, in which the peaks at ∼71 and ∼74 eV were assigned to 4 f 7/2 and 4 f 5/2 orbitals of metallic Pt. Impressively, the Pt signal shifted from 71.03 eV (Pt 3 Bi 1 ) to 70.70 eV (Pt 1 Bi 2 ) with the increasing Bi content, suggesting an electron transfer between Pt and Bi by the incorporation of Bi species to induce an electron-rich state of Pt, which may accelerate the CO ads desorption according to previous works. ,, For the XPS results of Bi 4 f orbitals (Figure c), three peaks at ∼157.0, ∼157.7, and ∼159 eV can be indexed as Bi 0 , Bi δ+ , and Bi 3+ species, repectively. , The existence of metallic Bi further confirmed the generation of Pt 1 Bi 1 alloys. In addition, the enhanced Bi feeding can gradually increase the proportion of Bi 0 in the Pt x Bi y nanostructures, indicating the formation of more stable Pt 1 Bi 1 alloys rather than the pure oxophilic Bi metal.…”

“…Impressively, the Pt signal shifted from 71.03 eV (Pt 3 Bi 1 ) to 70.70 eV (Pt 1 Bi 2 ) with the increasing Bi content, suggesting an electron transfer between Pt and Bi by the incorporation of Bi species to induce an electron-rich state of Pt, which may accelerate the CO ads desorption according to previous works. 36,45,46 For the XPS results of Bi 4f orbitals (Figure 3c), three peaks at ∼157.0, ∼157.7, and ∼159 eV can be indexed as Bi 0 , Bi δ+ , and Bi 3+ species, repectively. 47,48 The existence of metallic Bi further confirmed the generation of Pt 1 Bi 1 alloys.…”

“…As highly dispersed supported Pt catalysts, the most typical representative is the commercial Pt/C catalyst, in which the high-loading (20–40 wt %) Pt nanoparticles (NPs, ∼3 nm) supported on amorphous carbon-based materials. , However, the high surface energy and the mass loading of small size Pt NPs lead to their agglomeration during electrocatalysis, which reduced the amount of active sites and was highly susceptible to the poisoning of the adsorbed CO (CO ad ) intermediate. , To overcome the above issues, considerable works mainly focused on synthesizing Pt NPs with superior geometric structures or combining Pt NPs with other active and promotional components, − which can tune their electronic structures. , Among them, it is promising to prepare efficient and stable Pt catalysts via constructing unique heterogeneous structures. Taking bismuth (Bi) as an example, the introduction of Bi species into a Pt nanocrystal would downshift the d -band center of Pt, while the oxidative removal of CO ad adjacent the Pt active sites can be accelerated by the incorporation of a Bi oxide or hydroxide. − Despite the advantages of heterogeneous structures, most studies have mainly focused on performance improvement, while studies on the relationship between geometric structure and electrochemical stability of Pt-based heterogeneous structures have generally been neglected. − In addition, relatively little attention has been paid to investigating the effects of structural variation caused by the incorporation of the second component on EOR performance. As mentioned above, it is highly urgent to systematically study the key issues, which will facilitate the development of high-efficiency EOR electrocatalysts.…”

Achieving superior methanol oxidation electrocatalytic performance by surface reconstruction of PtNi nanoalloys during acid etching process

“…The introduction of Ni element can change the d-band center of Pt, adjusting the adsorption strength of the poisonous intermediates and promoting the activation of water to generate OH ads species at lower potentials, which can facilitate the electrocatalytic performance. 51 Moreover, the binding energy of the Pt 4f peak of Pt 1.5 Ni-NGA exhibits a positive shift trend (∼0.25 eV) compared to PtNi 3 -NGA due to the surface electronic change induced by acid etching, and compared with Pt/ C, the peak for Pt 4f of Pt 1.5 Ni-NGA exhibits the obvious positive shift of approximately 0.7 eV. The significant positive shift of Pt 1.5 Ni-NGA results in a lowered Pt d-band center, weakening the adsorption strength of the CO ads intermediates on the active sites.…”

Toward Electrocatalytic Methanol Oxidation Reaction: Longstanding Debates and Emerging Catalysts

“…[ 7–10 ] In contrast, the poor stability and sluggish kinetics make MOR become the bottleneck of DMFCs and restrict their commercialization. [ 11–13 ]…”