Comparison of Commercial and Lab-made MWCNT Buckypaper: Physicochemical Properties and Bioelectrocatalytic O2 Reduction

Buckypapers have emerged as an important material for the construction of enzyme-based electrodes and biofuel cells for energy harvesting. In this work, commercial and lab-made buckypapers have been compared to establish their properties for future use as advanced bioelectrodes. The physical properties of the paper-like carbon nanotube films were characterised by electron microscopy, four-point probe conductivity, X-ray photoelectron spectroscopy and Raman spectroscopy. The electrochemical properties were investigated by voltammetry in the absence and presence of redox probes. Bioelectrocatalytic oxygen reduction was evaluated with iron-protoporphyrin modified buckypapers after immobilisation of bilirubin oxidase. Lab-made buckypaper exhibited a wider potential window, lower background capacitance, and cleaner voltammetry compared to commercial buckypaper. The catalytic current of lab-made buckypaper was 10-fold larger due to factors which include the 10-fold larger BET surface area, higher enzyme loading, more defective structure, and the smaller nanotube diameters. The presence of porphyrin groups enhanced the catalytic current in O-2-saturated solution up to 0.5mAcm(-2) and 1.3mAcm(-2) for commercial and lab-made buckypaper, respectively. This work sheds new light on the effects of various physicochemical properties on the electrochemical and DET-type bioelectrocatalytic activity of buckypapers, and promises to be important for the development of bioelectronics devices.