Thermal reduced graphene oxide enhanced in-situ HO generation and electrochemical advanced oxidation performance of air-breathing cathode.

Developing highly efficient catalysts with high ORR activity and HO selectivity is an important challenge for producing HO through 2e oxygen reduction reaction (ORR). In this work, we tuned the reduction degree of graphene oxide by controlling reducing temperature and prepared graphite-TRGO hybrid air breathing cathodes (ABCs). The HO production rate of TRGO-1100 (with highest reduction degree) modified ABC exhibits highest HO generation rate of 20.4 ± 0.8 mg/cm/h and current efficiency of 94 ± 2%. The charge transfer resistance of TRGO-1100 decreases by 2.5-fold compared with pure graphite cathode. Unreduced GO shows high HO selectivity and low ORR activity, while TRGO shows lower HO selectivity but higher ORR activity. Though the 2e ORR selectivity of TRGO decreased TRGO with all reduction degrees, the HO production increased in all forming electrodes. Superior performance of TRGO modified ABCs is attributed to high oxygen adsorption and low charge transfer resistance. TRGO possesses super-hydrophobicity and large surface area for oxygen adsorption. Besides, TRGO provides abundant electrochemically active sites to facilitate the electron transfer and formed more mesopores for HO release. Electro-Fenton using TRGO-1100-ABC exhibited great performance for Persistent Organic Pollutants (POPs) degradation, which removed 66% of tetracycline in 5 min.