Achieving Highly Electrocatalytic Performance by Constructing Holey Reduced Graphene Oxide Hollow Nanospheres Sandwiched by Interior and Exterior Platinum Nanoparticles

Abstract

graphene nanosheets are considered as an attractive support to load metal nanoparticles for applications in fuel cells due to their extraordinary physicochemical properties arising from the 2D nanostructure. However, fabricating graphene/metal nanoparticle nanohybrids with superior electrochemical performance remains a great challenge to date. In this work, we, for the first time, demonstrate a novel and ingenious approach to fabricate holey reduced graphene oxide hollow nanospheres sandwiched by interior and exterior Pt nanoparticles (denoted as Pt@holey r-GO@Pt hollow nanospheres), using uniform SiO 2 nanospheres as the templates. The Pt@holey r-GO@Pt hollow nanospheres represent a new type of metal/graphene heteroarchitecture due to their rich porosity, abundant active sites, facilitated reaction kinetics, and outstanding structural stability. Thanks to these distinguished merits, the as-prepared Pt@holey r-GO@Pt hollow nanospheres exhibit greatly enhanced electrocatalytic performances toward the oxygen reduction reaction and methanol oxidation reaction as compared with the intact counterparts and commercial Pt/C catalyst, showing great potential in fuel cell devices. The smart strategy outlined here should be readily applicable to rational design of other graphene/metal nanoparticle nanohybrids for energy storage and conversion applications in the future.

Isolated Fe Single Atomic Sites Anchored on Highly Steady Hollow Graphene Nanospheres as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

“…Raman spectra of pristine GO nanosheets and Fe–N x ISAs/GHSs in Figure b exhibit two well‐defined peaks, the D band at ≈1366 cm −1 ascribed to defects and disordered carbon and G band at ≈1613 cm −1 corresponding to sp 2 ‐hybridized carbon. Obviously, the Fe–N x ISAs/GHSs show a lower ratio of the D band to G band intensity ( I D / I G ), indicative a well‐crystallized graphitic carbon and high conductivity of the Fe–N x ISAs/GHSs . The N 2 adsorption–desorption isotherms (Figure S6, Supporting Information) of the Fe–N x ISAs/GHSs can be classified as type‐IV curves, suggesting the presence of mesopores.…”

“…Importantly, no diffraction peaks related to Fe-based species emerges, proving that Fe atoms are atomically dispersed in the Fe-N x ISAs/GHSs. [31] The N 2 adsorption-desorption isotherms ( Figure S6 Supporting Information) of the Fe-N x ISAs/GHSs can be classified as type-IV curves, suggesting the presence of mesopores. While being loaded on 2D graphene nanosheets, FePc molecules also transform into plenty of Fe-based nanoparticles after the carbonization treatment, as evidenced by the small diffraction peaks in the XRD pattern ( Figure S5a, Supporting Information) and the TEM image ( Figure S5b, Supporting Information).…”

“…Among various substrates, 2D graphene-based nanosheets are regarded as a class of promising candidate because of their large surface area, outstanding mechanical robustness and superior electrical conductivity. [29][30][31] Therefore, 3D graphene hollow nanospheres are deservedly expected as an ideal platform to immobilize isolated Fe single atoms. [26][27][28] To this end, we have recently developed a sophisticated and universal template-engaged strategy to fabricate 3D graphene hollow nanospheres, which could exhibit improved mechanical strength, accelerated reaction kinetics, and enhanced electrocatalytic performance when served as a catalyst support.…”

“…Unfortunately, the irreversible stacking of 2D graphene nanosheets would diminish the accessible surface, bury the catalytically active sites and obstruct the mass diffusion/transport, thereby posing a negative effect to electrocatalytic performance . To this end, we have recently developed a sophisticated and universal template‐engaged strategy to fabricate 3D graphene hollow nanospheres, which could exhibit improved mechanical strength, accelerated reaction kinetics, and enhanced electrocatalytic performance when served as a catalyst support . Therefore, 3D graphene hollow nanospheres are deservedly expected as an ideal platform to immobilize isolated Fe single atoms.…”

Low‐Load Pt Nanoclusters Anchored on Graphene Hollow Spheres for Efficient Hydrogen Evolution

“…Meanwhile, 3D GHSs can effectively overcome the weakness of 2D graphene (e.g., stacking), acting as a highly effective carbon support to enhance the mechanical strength of electrocatalysts, promote the reaction kinetics, and thus improve the electrocatalytic properties. [ 31,53,54 ] Turnover frequency (TOF) could reveal the intrinsic per‐site activity of a catalyst. Pt/GHSs displays the highest TOF of 0.002 s −1 at the overpotential of 27 mV (details in Supporting Information), addressing the superior HER activity of Pt/GHSs.…”