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) (123 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-1 h(-1) (0.079 kg m(-3) day(-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. (C) 2015 Elsevier B.V. All rights reserved.