Mesoporous PdBi nanocages for enhanced electrocatalytic performances by all-direction accessibility and steric site activation

Abstract

An effective yet simple approach was developed to synthesize mesoporous PdBi nanocages for electrochemical applications. This technique relies on the subtle utilization of the hydrolysis of a metal salt to generate precipitate cores in situ as templates for navigating the growth of mesoporous shells with the assistance of polymeric micelles. The mesoporous PdBi nanocages are then obtained by excavating vulnerable cores and regulating the crystals of mesoporous metallic skeletons. The resultant mesoporous PdBi nanocages exhibited excellent electrocatalytic performance toward the ethanol oxidation reaction with a mass activity of 3.56 A mg^-1_Pd, specific activity of 17.82 mA cm^-2 and faradaic efficiency of up to 55.69% for C1 products.

Fig. 1. Schematic illustration of the preparation of meso-PdBi nanocages.

Fig. 2. (a and b) SEM images of the obtained products (a) before and (b) after HCl etching treatment. (c–e) HAADF-STEM image and corresponding elemental maps (Pd (red) and Bi (green)).

Fig. 3. (a and b) HAADF-STEM images of an individual mesoporous PdBi nanocage. (c) High-resolution HAADF image of a surface region of the meso-PdBi nanocages. False color is applied to enhance the contrast. (d) Lattice profiles of the selected lines in panel (c). (e) Aberration-corrected HAADF image of the PdBi nanocage surface. The dashed arrows show the lattice distortion in panel (e).

Fig. 4. (a) CV curves recorded in 0.5 M H₂SO₄ at a scan rate of 50 mV s⁻¹ of different electrocatalysts. (b) CV, (c) LSV and (e) chronoamperometric curves (recorded at −0.2 V) for the EOR in 1.0 M KOH containing 1.0 M C₂H₅OH. The CV and LSV curves were obtained at scan rates of 50 mV s⁻¹ and 1.0 mV s⁻¹, respectively. (d) Histogram of the mass and specific activities of different catalysts for the EOR. (f) FEs of the major products of the EOR at different potentials catalyzed by: meso-PdBi nanocages, meso-Pd NPs and PdB (from left to right for each potential).

Fig. 5. XPS patterns of (a) Pd 3d and (b) Bi 4f of meso-PdBi nanocages and meso-Pd NPs. (c–e) LSVs of the EOR catalyzed by (c) meso-PdBi nanocages, (d) meso-Pd and (e) PdB in 1.0 M KOH containing 1.0 M C₂H₅OH at different scan rates. (f) The relationship of the peak current versus the square root of the scan rate.