Accelerated bubble growth and departure by bioinspired gradient anode in microfluidic fuel cells

Membraneless microfluidic fuel cell (MMFC) is expected to be a promising candidate of next-generation power supplies for portable devices due to its intrinsic advantages of compact construction, sufficient power density and environmental friendliness . However, it remains a challenge to CO 2 bubbles management with a controllable strategy under the acidic operational conditions. Herein, a facile and effective strategy that enables promotion of CO 2 bubbles detachment by manipulating the generated CO 2 bubbles with the aid of bioinspired gradient anode is proposed. The geometry gradient successfully boosts CO 2 bubbles transport along flow direction and wettability-gradient facilitates the unidirectional CO 2 bubbles penetration. The successful cooperation can benefit the manipulation of CO 2 bubble generation, transport, and departure on the anode. The MMFC equipped with the proposed anode is capable of operating stably at the extremely high current density of 130 mA cm −2 . Compared with MMFC based on the conventional anodes, the power density and the limiting current density are significantly increased by 30% and 60%, respectively. The present study solves the problem of unstable power supply caused by CO 2 bubbles at high current density (>50 mA cm −2 ), benefiting the powering the practical devices constantly.