Guest Seminar - Sustainable Carbon Materials for Energy and Environmental Applications

Carbon materials can play an essential role in creating a more sustainable future. This talk introduces two research topics currently conducted in Advanced Carbon Research Lab at the University of Sydney. First, methane pyrolysis (CH4 → 2H2 + C) is a promising H2 production method with low CO2 emissions. Utilizing its solid carbon coproducts is critical for its economic competitiveness. Catalytic CH4 pyrolysis using low-cost Fe ore catalysts yields carbon nano-onions encapsulated with magnetic Fe cores (Fe@CNO). Fe@CNO can serve as efficient and recyclable Fenton catalysts for pollutant degradation. Further, Fe@CNO has a high adsorption capacity for antibiotics in wastewater. Surface oxidized Fe@CNO also presents a high catalytic activity for in situ electrochemical H2O2 production. An integrated Fe@CNO-enabled wastewater treatment process was demonstrated. Fe@CNO was further purified by standard high-temperature thermal treatment or an alternative new electrochemical method to reach the purity of 99.3 and 97.6 wt.%, respectively. Purified CNO is demonstrated as a high-performance conductive additive in primary zinc-carbon batteries and rechargeable lithium-ion batteries, anode materials in lithium-ion batteries, and cathode and anode materials in dual-carbon batteries. These open the opportunity to turn carbon co-products from H2 production into value-added carbon commodities, avoiding waste generation and offsetting H2 production costs. Second, iron–nitrogen–carbon (Fe–N–C) single-atom catalysts are promising precious metal-free catalysts for various essential reactions. However, poor stability is a roadblock to their practical applications. A series of heterogeneous molecular catalysts with well-defined structures were used as model catalysts to map their degradation for oxygen reduction reactions in acidic electrolytes. Five degradation paths were quantified, and the beneficial role of electron-withdrawing substituents was revealed. Further, adding organic molecules with suitable properties as scavengers of reactive oxygen species can alleviate Fe–N–C degradation. Matching organic molecule size with the pore structure of Fe-N-C catalysts other than their radical scavenging speed is more critical. The large dimethyl sulfoxide, having detrimental effects on Fe–N–C with abundant micropores, can significantly reduce the degradation of Fe–N–C with abundant mesopores.