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Use of nonimmobilized enzymes and mediators achieved high power densities in closed biobatteries

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The immobilization of redox enzymes on the surface of electrodes is a typical practice for enzymatic fuel cells (EFCs) but enzyme immobilization usually results in low retaining enzymatic activities and low power densities. Here, we investigated an alternative solution – the use of nonimmobilized thermostable enzymes (e.g., NAD-based glucose 6-phosphate dehydrogenase and flavin-containing diaphorase) and a nonimmobilized mediator (i.e., benzyl viologen or 9,10-anthraquinone-2,7-disulphonic acid, AQDS) for achieving high power densities from glucose 6-phosphate in closed EFCs (called biobatteries). At the same enzyme loading, power densities of biobatteries increased in an order from the case of immobilized enzymes and immobilized vitamin K3 to the case of nonimmobilized enzymes and immobilized vitamin K3 to the case of nonimmobilized enzymes and nonimmobilized AQDS. The maximum power density of the biobattery based on nonimmobilized enzymes and AQDS was 1.1 mW cm
2 of anode at room temperature, 34-times of the biobattery based on immobilized enzymes and immobilized vitamin K3. When enzyme loading was increased by another 10-fold, the highest power density of biobattery was increased to 2.4 mW cm
2 at 37°C. The biobattery based on nonimmobilized enzymes and AQDS retained 60% of its initial current density after running for 2 h. When repeatedly being used for 6 rounds, the biobattery had 35% of its initial current density after 12 days. Our results suggest that closed biobatteries
equipped with nonimmobilized thermostable enzymes and mediators feature simple system configuration and have high power densities.

Keywords
Biobattery, enzymatic fuel cell, enzyme immobilization, nonimmobilized mediator,thermostable enzyme

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Judul Seri

Energy Science and Engineering

No. Panggil

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Penerbit

: The Authors., 2015

Deskripsi Fisik

Energy Science and Engineering 2015; 3(5): 490–497

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English

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FISIKA

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