Bridging the Surface Charge and Catalytic Activity of a Defective Carbon Electrocatalyst

Abstract

Electrocatalysis is dominated by reaction at the solid–liquid–gas interface; surface properties of electrocatalysts determine the electrochemical behavior. The surface charge of active sites on catalysts modulate adsorption and desorption of intermediates. However, there is no direct evidence to bridge surface charge and catalytic activity of active sites. Defects (active sites) were created on a HOPG (highly oriented pyrolytic graphite) surface that broke the intrinsic sp2‐hybridization of graphite by plasma, inducing localization of surface charge onto defective active sites, as shown by scanning ion conductance microscopy (SICM) and Kelvin probe force microscopy (KPFM). An electrochemical test revealed enhanced intrinsic activity by the localized surface charge. DFT calculations confirmed the relationship between surface charge and catalytic activity. This work correlates surface charge and catalytic activity, providing insights into electrocatalytic behavior and guiding the design of advanced electrocatalysts.

Charge Polarization from Atomic Metals on Adjacent Graphitic Layers for Enhancing the Hydrogen Evolution Reaction

“…This transformation enhances the adsorption of protons to the catalyst, thus promises am ore stable adsorption state of the intermediate in the HER. [18] Thee nergy profiles in Figure 3b shows that the theoretical Gibbs free energy to drive HER of 2(a(Co-Pt)@N8V4) is 0.08 V, which is lower than those of a(Co-Pt)@N8V4 and Pt/C.T he significant free-energy decreased from a(Co-Pt)@N8V4 to 2(a(Co-Pt)@N8V4) is probably ascribed to the strong adsorption of H* with the advantage of concentrated negative charges.T ov alidate the interaction of atomic metals trapped on the adjacent graphitic layers, control samples of A-CoPt-NG and A-CoPt-MNG with atomic Co and Pt trapped on single layer graphene and multilayer graphene were prepared, respectively.T hey were fabricated from the atomic Co trapped graphene with nitrogen dopants (Co-NG and Co-MNG) via the same electrochemical activations.M etal particles are absent in A-CoPt-NG (Supporting Information, Figure S10), but apparent signals of Co and Pt are observed from the energy-dispersive X-ray spectroscopy (EDS) elemental mapping images,i ndicating that Co and Pt are trapped on the graphene atomically. TheR aman spectra (Supporting Information, Figure S11) show that the 2D band of A-CoPt-NG around 2650 cm À1 is as ymmetric Lorentzian peak, indicating the single layered structure.However,the 2D band of A-CoPt-MNG splits and is shifted to high frequency,i mplying the multilayered structure.T he Pt contents of A-CoPt-MNG and A-CoPt-NG are 0.05 wt %a nd 0.03 wt %, respectively.W hen the Ag was photo-deposited (Supporting Information, Figure S12), there are more Ag particles on the surface of A-CoPt-MNG…”

Charge Polarization from Atomic Metals on Adjacent Graphitic Layers for Enhancing the Hydrogen Evolution Reaction

“…The most significant change is the vanishment of charge depletion on the outside surface of the outmost layer. This transformation enhances the adsorption of protons to the catalyst, thus promises a more stable adsorption state of the intermediate in the HER . The energy profiles in Figure b shows that the theoretical Gibbs free energy to drive HER of 2(a(Co‐Pt)@N8V4) is 0.08 V, which is lower than those of a(Co‐Pt)@N8V4 and Pt/C.…”

Heterogeneous Mo2C/Fe5C2 Nanoparticles Embedded in Nitrogen‐Doped Carbon as Efficient Electrocatalysts for the Oxygen Reduction Reaction

“…The intensity ratio between G and D bands ( I D / I G ) in Mo 2 C/Fe 5 C 2 @NC is associated with treatments of different temperature, reaching a maximum in Mo 2 C/Fe 5 C 2 @NC‐800. The intensity ratio of the D and G band ( I D / I G ) is widely used to assess the graphite material defect density , . The I D / I G values of Mo 2 C/Fe 5 C 2 @NC‐700, Mo 2 C/Fe 5 C 2 @NC‐800 and Mo 2 C/Fe 5 C 2 @NC‐900 are measured to be 1.01, 1.08, 0.96, respectively.…”