Three-Dimensional Heteroatom-Doped Nanocarbon for Metal-Free Oxygen Reduction Electrocatalysis: A Review

Abstract

Abstract:The oxygen reduction reaction (ORR) at the cathode is a fundamental process and functions a pivotal role in fuel cells and metal-air batteries. However, the electrochemical performance of these technologies has been still challenged by the high cost, scarcity, and insufficient durability of the traditional Pt-based ORR electrocatalysts. Heteroatom-doped nanocarbon electrocatalysts with competitive activity, enhanced durability, and acceptable cost, have recently attracted increasing interest and hold great promise as substitute for precious-metal catalysts (e.g., Pt and Pt-based materials). More importantly, three-dimensional (3D) porous architecture appears to be necessary for achieving high catalytic ORR activity by providing high specific surface areas with more exposed active sites and large pore volumes for efficient mass transport of reactants to the electrocatalysts. In this review, recent progress on the design, fabrication, and performance of 3D heteroatom-doped nanocarbon catalysts is summarized, aiming to elucidate the effects of heteroatom doping and 3D structure on the ORR performance of nanocarbon catalysts, thus promoting the design of highly active nanocarbon-based ORR electrocatalysts.

3D Carbon Materials for Efficient Oxygen and Hydrogen Electrocatalysis

“…Therefore, for cost and stability reasons, new catalysts for the ORR are highly sought after. Attention in recent years has focused on transition metal active centers in carbon matrices, especially where the carbon is doped with heteroatoms such as nitrogen, though the presence of metal in these materials leads to significant durability challenges, again, particularly in acidic media, and so a new class of entirely metal‐free ORR catalysts has emerged in recent years as cost effective, durable, and electrochemically selective alternatives to traditional materials …”

“…Additionally, 1D or 2D catalysts can be difficult to process into working electrodes and may suffer from a lack of mechanical robustness or re‐staking of nanomaterials. Therefore, 3D carbon structures including varying porosity have recently been seen as routes to scalable, high‐performance electrodes for the ORR, including the possibility of free‐standing electrodes . Such is the interest in the field of heteroatom‐doped carbons for metal‐free ORR catalysts, the number of publications is rapidly increasing year on year.…”

“…Such is the interest in the field of heteroatom‐doped carbons for metal‐free ORR catalysts, the number of publications is rapidly increasing year on year. Several recent reviews give good overviews of the progress in the area, and as the publication rate is high, this section will focus mainly on work since those reviews were published, as well as on 3D‐doped carbons in preference to 1D or 2D.…”

Theoretical investigation of the ORR on boron–silicon nanotubes (B–SiNTs) as acceptable catalysts in fuel cells

“…Stevenson et al 53 proved in ORR the O 2 in a 2-electron path is reduced to form OOH on carbon nanotubes. Hu and Xiong et al 54,55 conrmed that nitrogen and boron-doped nanostructures as ORR catalysts have low price, great durability and excellent potential. Zhao and Wei et al 56,57 conrmed the doping of carbon nanotubes have vital roles on performance of ORR.…”

Novel Non-Precious Metal Electrocatalysts for Oxygen Electrode Reactions

“…Herein, one review paper and five research articles pay special attention to ORR high-performance electrocatalysts. For example, Xiong et al [9] summed up recent progress on three-dimensional hetero-atom-doped nanocarbon for metal-free ORR electrocatalysis; Schardt et al [10] carefully investigated the influence of the structure-forming agent on the composition, morphology and ORR performance of Fe-N-C electrocatalysts; Zhu et al [11] developed a novel metal-organic framework route to embed Co nanoparticles into multi-walled carbon nanotubes for ORR in alkaline media; Liu et al [12] fabricated N,S co-doped carbon nanofibers derived from bacterial cellulose/poly(methylene blue) hybrid for ORR; Liu et al[13] prepared porous Fe-N-S/C electrocatalysts for ORR in a Zn-air battery using g-C 3 N 4 and 2,4,6-tri(2-pyridyl)-1,3,5-triazine as binary nitrogen precursors; Zeng et al [14] reported the Ag 4 Bi 2 O 5 /MnO 2 corn/cob-like nanomaterial as a superior catalyst for ORR in alkaline media. One review paper and one research article are involved in the OER electrocatalysts.…”