Thermally Stable Super Ionic Conductor from Carbon Sphere Oxide.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Development of stable proton conductors is crucial for advanced energy technologies.
• Conventional carbon-based proton conductors often suffer from limited thermal stability.
• Graphene oxide (GO) is a known proton conductor but can degrade at elevated temperatures.

Purpose of the Study:

• To synthesize and characterize a highly stable proton conductor from carbon sphere oxide (CSO).
• To evaluate the proton conductivity and thermal stability of CSO compared to graphene oxide (GO).
• To explore the potential applications of CSO in high-temperature devices.

Main Methods:

• Carbon spheres (CS) were synthesized from sucrose and subsequently oxidized to CSO using Hummers' graphite oxidation technique.
• Proton conductivity was measured at room temperature and 90% relative humidity using a thin layer of CSO on a microsized comb electrode.
• Thermal stability was assessed by annealing CSO at various temperatures and measuring its proton conductivity.

Main Results:

• CSO exhibited a proton conductivity of 8.7×10⁻³ S cm⁻¹ at 90% relative humidity, surpassing GO (3.4×10⁻³ S cm⁻¹).
• The activation energy (Ea) of 0.258 eV indicates proton conduction via the Grotthuss mechanism, primarily attributed to carboxyl functional groups.
• CSO maintained stable morphology and reproducible proton conductivity up to 400°C, unlike GO which decomposes around 80°C.

Conclusions:

• Carbon sphere oxide (CSO) is a highly stable and efficient proton conductor.
• CSO demonstrates superior thermal stability and reproducible conductivity compared to graphene oxide (GO).
• CSO is a promising material for solid electrolytes in high-temperature fuel cells and sensing devices.