Abstract
Multiple heteroatom-doped graphene is of great interest for developing an efficient electrocatalyst for oxygen reduction reaction (ORR). To maximize the electrocatalytic performance of doped graphene, the competitive doping mechanism caused by the different atomic sizes of dopants should be developed. Herein, three different heteroatoms (e.g., N, P and B) are competitively introduced into reduced graphene oxide (RGO) using both single- and two-step processes. The total quantity of heteroatoms for ternary RGO synthesized using the two-step process is lower than that when using the single-step process. Higher ORR electrocatalytic activity for the two-step-synthesized RGO compared to the single-step-synthesized RGO can be explained by: (a) a high amount of P atoms; (b) the fact that B doping itself decreases the less electrocatalytic N moieties such as pyrrole and pyridine and increases the high electrocatalytic moieties such as quaternary N; (c) a high amount of B atoms itself within the RGO act as an electrocatalytic active center for O2 adsorption; and (d) a small amount of substitutional B might increase the electrical conductivity of RGO. Our findings provide new insights into the design of heteroatom-doped carbon materials with excellent electrocatalytic performance.
Highlights
There is no distinctive difference in microtexture between NPRGO and NPBRGO depending on the quantity and type of heteroatoms
The homogeneous introduction of N, P, and B atoms into the graphene matrix were identified from EELS elemental mapping images of ternary doped reduced graphene oxide (RGO) obtained using two-step (Figure 1e–i) and one-step (Figure S2a–e), respectively
Ternary doped RGOs containing N, P, and B atoms were synthesized by a two-step doping process that uses DNA and B2O3 as dopant sources, and multiple-doped RGOs were evaluated as electrocatalysts for oxygen reduction reaction (ORR)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Identifying efficient catalysts for the cathodic oxygen reduction reaction (ORR) in fuel cells, photocatalytic water splitting, and metal-air batteries has been a critical research direction in recent years [1,2,3,4,5]. Noble metals have been considered as the most effective ORR catalysts, but they have experienced several drawbacks such as high cost, poor long-term durability, sluggish electron transfer kinetics, and susceptibility to carbon monoxide poisoning [6,7,8,9]. Active studies regarding the replacement of noble metal-based catalysts with efficient and inexpensive non-metal catalysts have been carried out [10]
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