Oxygen Reduction on Metal-Free Nitrogen-Doped Carbon Nanowall Electrodes

Abstract

A plasma-enhanced chemical vapor deposition (PECVD) process using a CH 4 :H 2 gas mixture creates vertically aligned carbon nanowalls (CNWs) on glassy carbon (GC) and Si substrates. Metal catalysts are not required for the nucleation and growth of CNWs on the substrates. The PECVD deposition temperatures and reaction times alter the morphology and thickness of the resulting CNW layer. A low-pressure, post-processing N 2 :Ar plasma treatment dopes the CNWs with nitrogen, and X-ray photoelectron spectroscopy measurements demonstrate that nitrogen is present at 4-20 atomic% with varying CN x bonding configurations dependent upon processing conditions. Raman spectroscopy shows relatively high intensity disorder bands (I D ) compared to lower intensity graphitic bands (I G ) indicating small crystalline domains. Rotating disk electrode voltammetry results show that the number of electrons (n) and kinetic current density (j k ) of the oxygen reduction reaction both increase with nitrogen content. In addition, n and j k increase with thickness of the nitrogen-containing CNW deposit. The results indicate that nitrogen-doped CNWs have higher electrochemical reactivity than their non-doped counterparts.

Vertically Aligned Graphene Nanosheet Arrays: Synthesis, Properties and Applications in Electrochemical Energy Conversion and Storage

“…In the absence of transition metals, VAGNAs with nitrogen doping has been demonstrated to increase the kinetic current and selectivity for ORR. [136] The Pt/VAGNA electrodes was elucidated to have much higher catalytic performance than commercial T-Pt/carbon-black, attributed to the domain boundaries that lowered the activation energy of O 2 dissociation on Pt particles and the energy barrier of the rate-limiting step in the ORR process. Pt NPs/VAGNA electrodes were also demonstrated to have higher current density for methanol oxidation in comparison with the commercially used Pt-carbon black electrodes, and the electrodes were shown to be more resistant to carbon monoxide poisoning.…”

Recent progress in electrocatalysts with mesoporous structures for application in polymer electrolyte membrane fuel cells

“…In recent years, nitrogen-doped carbon with N-containing polymers, ammonia, as well as nitrogen gas as the nitrogen source or the source of both nitrogen and carbon has been developed, which possesses good ORR activity. [103][104][105][106][107][108] Further developments on the combination of mesoporous carbon materials with heteroatom doping make metal-free catalysts a potential substitution for the Pt/C catalyst.…”

Untangling Cooperative Effects of Pyridinic and Graphitic Nitrogen Sites at Metal‐Free N‐Doped Carbon Electrocatalysts for the Oxygen Reduction Reaction

“…[4][5][6][7] Substantial efforts have been devoted to the fundamental understanding of the role of N-sites by means of experimental and theoretical methods. [8][9][10][11][12][13] This is a significant challenge, as N-doped nanocarbons typically contain a mix of different nitrogen moieties, including so-called substitutional or 'graphitic' N sites (NG) and pyridinic-N (NP) at edge sites and vacancies within the scaffold. It is therefore difficult to directly attribute the observed ORR activity of N-doped carbon electrocatalysts to specific active sites.…”