A Tandem Reaction System for Inactivation of Marine Microorganisms by Commercial Carbon Black and Boron-Doped Carbon Nitride

The Pureballast system, based on photocatalytic technology, can purify ships' ballast water. However, the efficiency of photocatalytic sterilization still needs to be improved due to the shortcomings of the photocatalyst itself and the complex components of seawater. In this work, a tandem reaction of electrocatalytic synthesis and photocatalytic decomposition of hydrogen peroxide (H2O2) was constructed for the inactivation of marine microorganisms. Using seawater and air as raw materials, electrocatalytic synthesis of H2O2 by commercial carbon black can avoid the risk of large-scale storage and transportation of H2O2 on ships. In addition, boron doping can improve the photocatalytic decomposition performance of H2O2 by g-C3N4. Experimental results show that constructing the tandem reaction is effective, inactivating 99.7% of marine bacteria within 1 h. The sterilization efficiency is significantly higher than that of the single way of electrocatalysis (52.8%) or photocatalysis (56.9%). Consequently, we analyzed the reasons for boron doping to enhance the efficiency of g-C3N4 decomposition of H2O2 based on experiments and first principles. The results showed that boron doping could significantly enhance not only the transfer kinetics of photogenerated electrons but also the adsorption capacity of H2O2. This work can provide some reference for the photocatalytic technology study of ballast water treatment.