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Significance Statement
Hydrogen peroxide (H2O2) is a valuable industrial product that has widely used for disinfection, pollution removal and decolorization. Li et al. recently showed that H2O2 can be efficiently produced by bioelectrochemical systems using a new carbon black graphite hybrid air-cathode, where wastewater can be treated at the anode simultaneously.
The air-cathode is able to passively get oxygen from air, so the supplement of electron acceptor is zero-energy-consuming. It is fabricated using rolling-pressed method with a catalyst layer and an air diffusion layer, which was highly reproducible and water pressure affordable according to their previous results. With this cathode, the H2O2 yield reached up to 11.9 mg L-1 h-1 cm-2 at the current density of 12.3 mA cm-2 with an optimized carbon black to graphite mass ratio of 1:5. Most importantly, they for the first time reported the contribution of air diffusion through cathode in bacteria assisted H2O2 production system. They found the oxygen reduced to H2O2 is mainly from the diffusion process (>66%), especially when a more negative cathode potential is applied (94% at -1.0 V).
These results reveal that cathodic oxygen supplement is a bottleneck in bioelectrochemical H2O2 production, and their novel hybrid air-cathode provides an efficient, energy saving and economical solution to this problem, which makes bioelectrochemical system as an authentic green technology to produce fresh H2O2.
Li et al.’s work represents a step forward in the comprehension of the mechanism of electrochemical H2O2 production using air-breathing cathode, providing a new insight on oxygen and H2O2 mass transport inside the cathode.
Carbon materials at different size and form, for example, large graphite sheets and small amorphous carbon particles with PTFE fiber, facilitates O2 reduction and H2O2 diffusing out into bulk solution. This novel and economical air-cathode is promising for industrial H2O2 production in the future.
Journal Reference
A novel carbon black graphite hybrid air-cathode for efficient hydrogen peroxide production in bioelectrochemical systems
Journal of Power Sources, Volume 306, 2016, Pages 495–502.
Nan Li1, Jingkun An1, Lean Zhou2, Tian Li2, Junhui Li2, Cuijuan Feng2, Xin Wang2
[expand title=”Show Affiliations”]- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China
Abstract
Carbon black and graphite hybrid air-cathode is proved to be effective for H2O2 production in bioelectrochemical systems. The optimal mass ratio of carbon black to graphite is 1:5 with the highest H2O2 yield of 11.9 mg L−1 h−1 cm−2 (12.3 mA cm−2). Continuous flow is found to improve the current efficiency due to the avoidance of H2O2 accumulation. In the biological system, the highest H2O2 yield reaches 3.29 mg L−1h−1(0.079 kg m−3day−1) with a current efficiency of 72%, which is higher than the abiotic system at the same current density. H2O2 produced in this system is mainly from the oxygen diffused through this air-cathode (>66%), especially when a more negative cathode potential is applied (94% at −1.0 V). This hybrid air-cathode has advantages of high H2O2 yield, high current density and no need of aeration, which make the synthesis of H2O2 more efficient and economical.
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