Boosting oxygen diffusion by micro-nano bubbles for highly-efficient H2O2 generation on air-calcining graphite felt

Abstract

Electrochemical H2O2 generation via oxygen reduction has to face dissolved oxygen transfer limitation in aeration system. To mitigate this problem, we proposed to boost oxygen diffusion by micro-nano bubbles (MNBs) for highly-efficient H2O2 generation on air-calcining graphite felt (GF600). The oxygen transfer coefficient and rate of MNBs were 0.160 min−1 and 0.382 kg m−3 h−1, about 4 times and 5 times greater than those of conventional aeration, respectively. As a result, the GF600 electrode under MNBs aeration could produce 140.4 ± 1.6 mg L−1 H2O2 with an ultrahigh coulombic efficiency of 97.8 ± 0.9%, but only 47.9 ± 2.5 mg L−1 H2O2 with 65.9 ± 3.7% under conventional aeration. By increasing the potential on the GF600 electrode, the H2O2 production showed the first rising then descending trend with and the optimized potential of −0.6 V. Besides, during 5 cycles the H2O2 production of GF600 was stably ranged from 124.8 mg L‒1 to 145.2 mg L‒1 with high coulombic efficiency of 94.3%−97.8% under MNBs aeration. Thus, micro-nano bubbles could effectively solve O2 mass transfer limitation, paving a promising way for in-situ synthesis of H2O2.