Electrochemically Deposited Nanoporous Gold Electrodes on a Carbon Substrate for Efficient Direct Electron Transfer with Bilirubin Oxidase

Direct electron transfer (DET)-based biocathodes are highly attractive for enzymatic energy devices due to their ability to operate without redox mediators and associated voltage losses. However, achieving efficient DET remains challenging due to limited control over enzyme–electrode coupling. Here, we demonstrate that controlling electrodeposition dynamics via a pulsed galvanostatic method enables the fabrication of nanoporous gold electrodes with enhanced bioelectrocatalytic performance. Compared to conventional chronoamperometric deposition, the pulsed approach produces more homogeneous nanostructures, offers a wider tunability concerning the electroactive surface obtained, along with different morphologies of gold nanostructures and variable gold grain sizes. In this article, we reported a catalytic current density up to –1.75 mA·cm –2 after optimization of our pulsed method. Importantly, the enhanced performance can be explained by increased electroactive surface area and a narrow tunneling-distance distribution (β· d 0 = 3.76), as revealed by electrokinetic modeling. This work highlights electrodeposition dynamics as a key parameter for engineering high-performance, mediator-free biocathodes for enzymatic energy conversion.