The as-designed poly(pyrr)–ABTS–pyr film. a, Representations of Trametes versicolor Lac 

with the hydrophobic binding pocket oriented towards the bottom of the page and the T1 

copper site located on one side of the enzyme at the base of a hydrophobic pocket, which 

acts as the binding site of the enzyme substrate. The remaining three copper atoms are 

bound on the T2 and T3 sites in a triangular cluster approximately 12 Å away towards the 

other side of the enzyme, where oxygen binds. b, Graphical depiction of the ET from the 

electrode  towards  Lac  through  poly(pyrr)–ABTS–pyr film. Credit: (c) 

2018 NatureEnergy (2018). DOI: 10.1038/s41560-018-0166-4

A team of researchers with members from institutions in Singapore, China and the U.K. has 

found a way to improve electron transfer in enzymatic biofuel cells. In their paper published 

in the journal Nature Energy, they describe their technique and how well it works. Huajie Yin 

and Zhiyong Tang with Griffith University in Australia and the National Center for Nanoscience 

and Technology in China, offer a News & Views piece on the work done by the team in the 

same journal issue.

Enzymatic biofuel cells are, as their name implies, a type of fuel cell based on enzymes as 

catalysts instead of expensive metals. Because of their potential, scientists have been eager 

to find ways to overcome problems that have inhibited commercial applications—they are 

expected to be much cheaper to make than those now in use.

Currently, enzymatic biofuel cells are inefficient, have a short lifespan and do not produce 

much power. These problems, the researchers note, are due to the difficulty in wiring enzym

es and electrode surfaces. In this effort, they claim to have overcome some of that difficulty 

by combining two previously developed methods aimed at solving the problem. The first 

method involves connecting an enzyme to the surface of an electrode in such a way as to 

allow the electrons to tunnel between the two—it is called direct electron transfer. The second 

method involves a mediator that is used help the transfer—it is called, quite naturally, 

mediated electron transfer.

The researchers combined the two approaches to take advantage of the benefits of each. 

They used laccase as the enzyme and designed a transfer system that connected to a 

special type of carbon nanotube surface to further improve electron transfer. The system was 

made of three parts, an ABTS compound (to serve as a mediator), situated between a 

polypyrrole group at one end and a pyrene group at the other.

In testing their technique, the team found that the maximum OOR current density reached as 

high as 2.45 mA/cm2 and their device was able to keep half of its ORR current for 120 days. 

They suggest their results show promise and expect further improvements as they refine the 

technique.