Biological electron transfer is fundamental to life on earth. Photosynthesis, respiration and many other biological processes are underpinned by electron transfer between redox proteins and catalysis by redox enzymes. Fully understanding the mechanisms of redox biology is crucial to understanding life and inspiration for chemical, biomedical and future energy technologies can be taken from Nature’s fine example. Developments in techniques and data analysis are required to gain a deeper understanding of biological electron transfer and redox catalysis. Protein film electrochemistry has enabled mechanistic insight into protein redox chemistry but has distinct limitations in the study of non-catalytic electron transfer as opposed to catalytic reactions. This thesis outlines the insight into biological redox chemistry gained through development of Fourier Transformed ac Voltammetry and associated analysis, in combination with spectroscopic, biochemical and molecular biology approaches. Novel pyranopterin ligand redox chemistry is proposed to control catalysis in a molybdoenzyme YedY, reversible disulphide bond redox chemistry is confirmed in a [NiFe]-hydrogenase maturation protein and an iron-sulphur cluster relay site distant from the active site is shown to influence the key catalytic properties of overpotential and bias in an O2-tolerant [NiFe]-hydrogenase.