Manipulation of Heteroatom Substitution on Nitrogen and Phosphorus Co-Doped Graphene as a High Active Catalyst for Hydrogen Evolution Reaction

Abstract

Graphene doped with heteroatoms is known to create a unique electronic structure with comparatively much higher active sites by the synergistic coupling effect. However, in the earlier attempts, the atomic structure of such co-doped graphene could not be altered; thus, there is a lack of reports discussing the influence of the atomic arrangement in the catalytic performance of the co-doped graphene. Here, by co-doping P and N atoms in graphene as a model system, we present a facile and two-step process wherein the sequence of doping helps in manipulating the heteroatom substitution, which is of great importance in defining better crystallinity and conductivity and favorable elemental functionalities and hence improving catalytic performance. The present method provides a clean, flexible, binder-free, and readily available electrocatalyst that avoids tedious conventional synthesis and device fabrication steps. The highest P-doping percentage (6 at. %) in the present work is superior to previous reports (3 at. %). By altering the sequence of N- and P-doping, the co-doped graphene electrode displayed excellent performance, with an increment of 148% in the sp2 domain size and enormous lowering in overpotential and Tafel slope (78%). Further, the efficiency of the hydrogen evolution reaction catalyst sustains >98% for 20 h, which is significantly higher than the well-known MoS x (63%). Although here the P–N co-doped system was utilized as a proof of concept, this method could be adapted for other versatile co-doped graphene. This work may pave the way for the development of co-doped graphene-based devices where manipulation of atomic arrangement can result in a structure with properties desirable for catalytic or electronics applications.

Recent Progress in Advanced Electrocatalyst Design for Acidic Oxygen Evolution Reaction

“…To activate pristine carbon materials, heteroatoms such as N, S, O, and P have to be doped into carbon matrix to induce charge polarization of carbon atoms, alter the electronic structure and local density of states, or introduce structural defects, which may possibly bring about distinct catalytic properties. [199][200][201][202] Heteroatom doped carbon materials have been widely used for efficiently catalyzing hydrogen evolution reaction, oxygen reduction reaction, electrochemical CO 2 reduction, oxygen evolution reaction, etc. [22,81,116,200,201] Regarding OER in acidic electrolytes, carbon based electrocatalysts including heteroatom doped carbon and hybrid carbon materials have been developed to boost the reaction kinetics.…”

Non‐N‐Doped Carbons as Metal‐Free Electrocatalysts

“…Along with the monodoped carbon catalysts discussed above, co‐doping of carbon materials with two or more different heteroatoms can further enhance the catalytic performance of the carbon catalysts by increasing the total number of active sites and through possible synergistic effects. [ 47 ] So far, co‐doping studies have been focused on co‐doping of N‐doped carbon materials with a second element, such as B, [ 69–76 ] S, [ 77–88 ] P, [ 89–106 ] and, to a less extent, Cl, [ 107 ] and Si. [ 108,109 ] A few reports on the co‐doping of carbon materials with three elements, such as N–P–S, [ 110,111 ] N–P–B, [ 112,113 ] N–P–F, [ 114 ] and N–S–F, [ 115 ] have recently appeared.…”

“…Current reports indicate that the sequence of doping helps in manipulating the heteroatom substitution, leading to a dramatic influence on the electrocatalytic properties. [ 95 ] Hung et al. found that the P doped graphene followed by the N‐doping is of great importance in defining a better crystallinity and conductivity and favorable elemental functionalities than the corresponding materials from the inverse doping sequencing.…”

Green Preparation of Fluorescent Nitrogen-Doped Carbon Quantum Dots for Sensitive Detection of Oxytetracycline in Environmental Samples

“…Heteroatomic doping of CQD not only improves fluorescence efficiency but also provides active sites in CQD to expand its potential applications in analysis and sensing [ 24 ]. Through the synergistic coupling effect, heteroatom-doped carbon materials can produce unique electronic structures with higher active sites [ 49 , 50 ]. In particular, nitrogen doping plays an important role in the regulation of electronic and chemical properties of carbon materials.…”