Mediatorless electrocatalytic oxygen reduction with catalase on mercury–gold amalgam microelectrodes

Catalase is known for its ability to catalyze disproportionation of hydrogen peroxide into oxygen and water. This work reports the oxygen reduction reaction (ORR) catalyzed by catalase, with a decreased activation energy manifested by a positive shift (+0.2 V) in onset potential. Direct bioelectrocatalysis with bovine liver catalase on a mercury–gold amalgam microelectrode is demonstrated. The background oxygen reduction reaction on the amalgam surface is inhibited by the protein, while the hydrogen evolution reaction (HER) is facilitated. Catalase molecules whose prosthetic groups are not wired to the electrode retain their intrinsic activity towards disproportionation of H2O2 generated at the electrode. The Hg–Au amalgam electrode may also be used to detect dissolved catalase in the absence of its substrate (H2O2) in the solution.