Electrospun carbon nitride supported on poly(vinyl) alcohol as an electrocatalyst for oxygen reduction reactions

Abstract

Electrochemical oxygen reduction reaction (ORR) via nonprecious catalysts has the potential for significant cost reduction in fuel cells. Dense, multi-layered poly(vinyl) alcohol (PVA) nanofibers dispersed with catalytically active carbon nitride (CN x ) nanoparticles were synthesized using electrospinning process. Size, morphology, elemental composition, bond structure of the CN x /PVA nanofibers were analysed using TEM, SEM, FTIR, XPS and Raman spectroscopic studies. Significant improvement in the electrocatalytic activity of CN x nanoparticles dispersed in the nanofibers as compared to its native form was observed towards ORR by voltammetry coupled with FTIR studies. Onset potential and peak current density observed for CN x /PVA nanofibers using cyclic voltammetry was comparable to conventional Pt/C (40:60 % by weight) catalyst. ORR mechanism was further analysed using RRDE and in-situ FTIR with linear sweep voltammetry studies. RRDE analysis confirmed that ORR takes place primarily via 4-electron pathway. The catalytic activity of CN x /PVA nanofibers for ORR was stable over 5000 repetitions of voltammetric studies coupled with FTIR.

Improvement in electrocatalytic activity of oxygen reduction reaction of electrospun carbon nitride/polyacrylonitrile nanofibers by addition of carbon black and Nafion® fillers

“…Synthesis of CN x nanoparticles CN x powder was synthesized from ethylene diamine (EDA) and carbon tetrachloride (CCl 4 ) by the process used by Jindal and Basu [17]. 110 mL EDA and 90 mL CCl 4 were stirred and refluxed in a container using a condenser at 90 C in nitrogen atmosphere for 6 h. The black viscous liquid formed was vacuum dried at 120 C. Calcination of the vacuum dried samples was carried out at 600 C for 5 h in nitrogen atmosphere.…”

“…However, CN x tends to agglomerate limiting its surface area [16]. In recent studies, we improved ORR catalytic activity of CN x by dispersing it on different supporting polymers (polyacrylonitrile (PAN) and poly(vinyl) alcohol (PVA)) using electrospinning technique [17,18]. Previously researchers have also used electrospinning technique to prepare N-doped carbon nanofibers as an efficient ORR electrocatalyst [19e21].…”

Direct Formic Acid PEM Fuel Cell with Electrospun Carbon Nitride Nanofibers as Cathode Catalyst

“…CN x nanofibers were synthesized using the same method employed in our previous studies . In brief, firstly CN x nanoparticles were synthesized using ethylenediamine (Merck) and carbon tetrachloride (Merck) as precursors.…”

“…For example, Noto et al utilised CN x matrix as a support material to embed PtNi x alloy nanoparticles as an effective ORR electrocatalyst. Moreover, literature suggests that CN x in its nanostructured form has shown to be a potential non‐Pt catalysts for ORR . CN x nanofibers are already reported to be synthesized using template method .…”

Local probe investigation of electrocatalytic activity

“…The capability of SECM to map the electrocatalytic activity of a catalyst layer is of great importance, considering that the layers are often not homogeneous. The possibility to perform conductivity measurements 57 with SECM is also an advantage, as it can ease the interpretation of the electrocatalytic activity results. Evidently, there are numerous appealing features of SECM which benefit electrocatalytic studies.…”