Graphitic Carbon Nitride Materials for Energy Applications

Abstract

Polymeric layered carbon nitrides were investigated for use as catalyst support materials for proton exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs). Three different carbon nitride materials were prepared: a heptazine-based graphitic carbon nitride material (gCNM), poly (triazine) imide carbon nitride intercalated with LiCl component (PTI-Li+Cl-) and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials were found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported Pt, Pt/PTI-Li+Cl- exhibited the best durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan. Superior methanol oxidation activity was observed for all gCNM supported Pt catalysts on the basis of the catalyst ECSA. Preliminary results on IrO2 supported on gCNM using a PEMWE cell revealed an enhancement in the charge-transfer resistance as the current density increases when compared to unsupported IrO2. This may be attributed to a higher active surface area of the catalyst nanoparticles on the gCNM support.

Pharaoh's Serpents: New Insights into a Classic Carbon Nitride Material

“…The observed asymmetry of the low-frequency peak could be due to structural inhomogeneity as well as the effect of 13 C, 14 N residual dipolar couplings, that are known to be significant at a relatively low magnetic field of 7.05 T. [40] In the single-pulse MAS experiment, which is better suited for quantitative estimates than CP-MAS, the shoulder at δ = 151 ppm is significantly smaller ( Figure S3a In their study of TGCN, Algara-Siller et al observed a broad resonance spanning a similar range (145-172 ppm with a maximum near 160 ppm) to that observed for the Pharaoh's serpent material [13] ( Figure S4, Supporting Information). Although their sample was nominally H-free, both 1 Figure S5, Supporting Information), [36] similar to those observed for the Pharaoh's serpent. The related crystalline compound PTI·LiCl also showed three peaks at 168, 162.6, and 157.9 ppm with relative intensities that evolved as a function of CP-MAS NMR contact times.…”

Carbon Nitride Materials as Efficient Catalyst Supports for Proton Exchange Membrane Water Electrolyzers

“…These mechanically produced composites did not exhibit competitive electrocatalytic (EC) performance when tested as anodes in a PEMWE cell, displaying a potential of 2.30 V at 0.42 A cm −2 , for a gCNH-IrO 2 (40%) composite compared with 1.85 V obtained for IrO 2 NPs at the same current density. However, electrochemical impedance measurements did indicate that the gCNH-IrO 2 composites showed enhanced charge transfer kinetics as the current density was increased, thus, suggesting ways to improve the EC performance [41]. Our results indicated that by developing a method to obtain a better distribution of the IrO 2 nanoparticles onto the gCNH substrate, a high-performance EC anode behavior could be obtained.…”

“…In a previous preliminary study, we had reported the preparation of gCNH-nano-IrO 2 composites by ball-milling mixtures of the two individual components together in isopropanol [41]. These mechanically produced composites did not exhibit competitive electrocatalytic (EC) performance when tested as anodes in a PEMWE cell, displaying a potential of 2.30 V at 0.42 A cm −2 , for a gCNH-IrO 2 (40%) composite compared with 1.85 V obtained for IrO 2 NPs at the same current density.…”

“…Our own work has recently demonstrated that graphitic or polymeric carbon nitride (gCNH) compounds show promising performance characteristics as support materials for Pt catalysts in PEM fuel cells [38,39,40,41,42,43,44]. …”

Graphitic Carbon Nitride-Graphene Hybrid Nanostructure as a Catalyst Support for Polymer Electrolyte Membrane Fuel Cells

“…However, all Pt supported on 3D aerogel materials are still significantly poorer than commercial Pt/C, with open circuit voltages (OCVs) at least 130 mV lower. Note that the performance of Pt/rGO is lower than that reported in the literature for in-situ PEM fuel cells (53), meaning that there is still scope for improvement in terms of aerogel pore size, ink formulation and electrode fabrication. Pt supported on bulk PTI is not shown, as the conductivity and surface area are too low to work in fuel cells.…”