Chemical Dopants on Edge of Holey Graphene Accelerate Electrochemical Hydrogen Evolution Reaction

Abstract

Carbon‐based metal‐free catalysts for the hydrogen evolution reaction (HER) are essential for the development of a sustainable hydrogen society. Identification of the active sites in heterogeneous catalysis is key for the rational design of low‐cost and efficient catalysts. Here, by fabricating holey graphene with chemically dopants, the atomic‐level mechanism for accelerating HER by chemical dopants is unveiled, through elemental mapping with atomistic characterizations, scanning electrochemical cell microscopy (SECCM), and density functional theory (DFT) calculations. It is found that the synergetic effects of two important factors—edge structure of graphene and nitrogen/phosphorous codoping—enhance HER activity. SECCM evidences that graphene edges with chemical dopants are electrochemically very active. Indeed, DFT calculation suggests that the pyridinic nitrogen atom could be the catalytically active sites. The HER activity is enhanced due to phosphorus dopants, because phosphorus dopants promote the charge accumulations on the catalytically active nitrogen atoms. These findings pave a path for engineering the edge structure of graphene in graphene‐based catalysts.

Engineered 2D Transition Metal Dichalcogenides—A Vision of Viable Hydrogen Evolution Reaction Catalysis

“…With the advantages of the low cost and easy fabrication, several heteroatom‐doped carbon materials have been reported for HER in recent years, including N, O, S, and P doped carbon nanomaterials. [ 166–170 ] Nevertheless, the HER catalytic performance of these materials reported so far are still poor (most Tafel slopes were larger than 100 mV dec −1 ) comparing with that of 2D TMDs. Besides, like the alloy and heteroatom‐doped carbon catalysts, several 2D TMDs are also highly conductive, i.e., the electrical conductivity of 10–100 S cm −1 of monolayered 1T MoS 2 sheet at room temperature, comparable to the best‐performing reduced graphene oxide sheet.…”

Electrocatalysis as the Nexus for Sustainable Renewable Energy: The Gordian Knot of Activity, Stability, and Selectivity

“…Moreover, the HER was faster on NP codoped G with edge structures, with a TOF of 0.64 H 2 s À1 at À200 mV (vs. RHE) compared to its edge-free counterpart with a TOF of 0.45 H 2 s À1 . [48] Most of the studies were performed in acidic electrolytes because of the favorable wetting properties. Recently, by using a soluble reversible redox species, a N 6 -coordinated Os complex, as an internal standard together with a rigorous measuring regime, TOF values in the range of 0.25 to 1.5 s À1 per Co atom in the potential range from 1.70 to 1.80 V (versus RHE) were determined for individual ZIF-67 MOF derived Co-C particles for the OER.…”

Reactive Plasma N-Doping of Amorphous Carbon Electrodes: Decoupling Disorder and Chemical Effects on Capacitive and Electrocatalytic Performance

“…However, this appears unlikely, as the changes in interfacial capacitance cannot justify the observed E on trend: the minimum capacitance of anC is lower than that of anC:Np5, while that of anC:Np20 samples is smaller than that of anC:Np10. Therefore, we propose that the most probable origin of improved onsets is an increase in the concentration of structural defects, such as edges and bond distortions, which have been proposed to be active sites in the electrocatalysis of the ORR (Favaro et al, 2013;Byers et al, 2014;Jia et al, 2016Jia et al, , 2019 and other reactions of importance for sustainable energy technologies (Dabo et al, 1998;Siahrostami et al, 2017;Kumatani et al, 2019). Finally, it is interesting to note that despite improvements in E on and values of n = 3 resulting from nitrogen plasma treatments, none of the anC:N carbon film electrodes displayed the high E on values (0.83 V RHE ) and remarkable selectivity (n = 4) observed for highly graphitized carbon thin films electrodes with low N/C content but ca.…”