Bismuth‐Noble Metal Alloy Nanostructures Prepared by Colloidal Chemical Routes for Use in Hydrogen Evolution and Oxygen Reduction Electrocatalysis: Bi‐Pt Versus Bi‐Pd

Abstract

oxidation reaction. In addition, an alteration of the active adsorption sites due to dilution of the catalytically active material may also take place when bimetallic catalysts are employed. Bismuth has already received interest as a Pt-modifier for electrocatalytic use. In this way, the noble metal quantity (and thus the overall cost) can be reduced, while the catalytic activity can be maintained (or even improved) by replacing a certain Pt amount with a less expensive metal. Bi may also modify the electronic structure of the Pt by lowering its d-band center. [1] Pt-Bi has been reported to be CO tolerant and it has exhibited higher catalytic performance for several oxidation reactions such as methanol, glycerol, ethylene glycol, and ethanol. The lower poisoning of Pt-Bi catalysts with CO has been proposed to be a determinant factor for the increase in catalytic activity of such materials. [2] Another example of an electrochemical reaction in which a bimetallic system can perform better than its monometallic counterpart is the electro-oxidation of formic acid. Pt-Bi showed a more negative onset potential and higher current density than monometallic Pt, together with the above-mentioned high tolerance to CO. [3] For the Pt-Bi alloy system, the PtBi 2 composition possesses a layered hexagonal crystal structure and has been suggested to behave as a 3D topological semimetal with very high magnetoresistance and unique electronic structures. A good comprehension of the electronic structure of PtBi 2 is required to properly assign the actual origin of its anomalous transport properties. [4] Pt-Bi bimetallic structures have found applications in thermoelectronics and batteries. Pt-Bi 2 O 3 has been shown to facilitate the photolysis of water, while single Pt or Bi 2 O 3 were unable to catalyze such reactions on their own. Pt-Bi/AC (activated carbon) is a commercially available catalyst for electrocatalysis and selective oxidation reactions. It has been suggested that Bi causes a geometric blocking effect on Pt, thus decreasing the active site ensemble of Pt. These decreased sites will still permit certain desired chemical reactions to occur, but they will not be active for specific undesired side reactions. The electronic properties of Bi help to increase the electrocatalytic activity of Pt, inhibiting poison effects, thanks to its small electron effective mass, low carrier concentrations, and highly anisotropic Fermi surface. [5,6] Pt-Bi alloy may not be the most suitable electrocatalyst for the oxygen reduction reaction (ORR); [7] still, though Pt-Bi catalysts Compositional and morphological tuning of bismuth-based nanomaterials is crucial to improve and broaden the application of such structures in a range of electrocatalytic reactions. Nanostructures composed of Pt-Bi and Pd-Bi alloys in different elemental proportions and shapes are produced by solvothermal and hydrothermal chemical routes at moderate temperatures. The alloying of cost-effective bismuth with platinum is found to be much more efficient than that with...

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Laser-Induced Synthesis of Electrocatalytically Active Ag, Pt, and AgPt/Polyaniline Nanocomposites for Hydrogen Evolution Reactions

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