From two-dimension to one-dimension: the curvature effect of silicon-doped graphene and carbon nanotubes for oxygen reduction reaction

Abstract

For the goal of practical industrial development of fuel cells, inexpensive, sustainable, and highly efficient electrocatalysts for oxygen reduction reactions (ORR) are highly desirable alternatives to platinum (Pt) and other rare metals. In this work, based on density functional theory, silicon (Si)-doped carbon nanotubes (CNTs) and graphene as metal-free, low cost, and high-performance electrocatalysts for ORR are studied systematically. It is found that the curvature effect plays an important role in the adsorption and reduction of oxygen. The adsorption of O2 becomes weaker as the curvature varies from positive values (outside CNTs) to negative values (inside CNTs). The free energy change of the rate-determining step of ORR on the concave inner surface of Si-doped CNTs is smaller than that on the counterpart of Si-doped graphene, while that on the convex outer surface of Si-doped CNTs is larger than that on Si-doped graphene. Uncovering this new ORR mechanism on silicon-doped carbon electrodes is significant as the same principle could be applied to the development of various other metal-free efficient ORR catalysts for fuel cell applications.

Synthesis, characterization and electrical properties of silicon-doped graphene films

“…[7][8][9] Until now, it has been reported that nitrogen, boron and sulfur atoms can be successfully doped into graphene and modulate its electrical and chemical properties. [16][17][18][19][20][21] However, it is difficult to dope silicon atoms into graphene lattice with stable Si-C bonds, because the atomic radius of silicon atom (117 pm) is much larger than that of carbon atom (77 pm). [16][17][18][19][20][21] However, it is difficult to dope silicon atoms into graphene lattice with stable Si-C bonds, because the atomic radius of silicon atom (117 pm) is much larger than that of carbon atom (77 pm).…”

Oxygen Reduction Reactions on Single‐ or Few‐Atom Discrete Active Sites for Heterogeneous Catalysis

“…From the computational research perspective, uneven charge and spin densities as a result of the electronegativity differences between the comprising elements of the catalytic motif is the main descriptor for ORR activity. Hence, the ORR activity can be triggered or enhanced by introducing curvature and defects, doping, and alloying . Binding energies with the intermediates species during the reaction is another important activity descriptor which has been emphasized for many nonmetal electrocatalysts.…”

“…Hence, the ORR activity can be triggered or enhanced by introducing curvature and defects, doping, and alloying. [195,196] Binding energies with the intermediates species during the reaction is another important activity descriptor which has been emphasized for many nonmetal electrocatalysts. Band structural modification due to the assembly of heteroatoms within the carbon framework is another widely studied mechanism to describe the catalytic performance of the materials.…”

Computational chemistry for graphene-based energy applications: progress and challenges

“…Zhang et al 226 investigated the catalytic effect of silicon dopants in graphene, alongside the effects of interfacial curvature. Their periodic PBE calculations (based on both an infinite graphene plane and a (10,0) carbon nanotube) indicated that O 2 adsorption strength over the Si dopant site increased when going from a convex, to flat, to a concave surface, with the corresponding free energy change of the rate-determining step in the ORR becoming lower.…”