In this work, three distinct heteroepitaxial single-crystal boron-doped diamond (SC-BDD) electrodes were fabricated and subjected to detailed surface analysis and electrochemical characterization. Specifically, the heteroepitaxy approach allowed to synthesize large-area (1 cm2) and heavily-doped (100)-oriented SC-BDD electrodes. Their single-crystal nature and crystal orientation were confirmed by X-ray diffraction, while scanning electron and atomic force microscopies revealed marked variations in surface morphology resulting from their growth on respective on-axis and off-axis substrates. Further, absence of sp2 impurities along with heavy boron doping (>1021 cm−3) was demonstrated by Raman spectroscopy and Mott-Schottky analysis, respectively. Cyclic voltammetry (CV) in a 0.1 M KNO 3 solution revealed wide potential windows (∼3.3 V) and low double-layer capacitance (<4 μF cm−2) of the SC-BDD electrodes. Their highly conductive, 'metal-like' nature was confirmed by CV with [Ru(NH 3) 6 ]3+/2+ probe manifesting near-reversible redox response with Δ E p approaching 0.059 V. The same probe was used to record scanning electrochemical micrographs, which clearly demonstrated homogeneously distributed electrochemical activity of the heteroepitaxial SC-BDD electrodes. Minor differences in their electrochemical performance, presumably resulting from the somewhat different morphological features, were only unveiled during CV with surface sensitive compounds [Fe(CN) 6 ]3−/4− and dopamine. The latter was also used to show the possibility of applying herein developed heteroepitaxial SC-BDD electrodes for electrochemical sensing, whereas experiments with anthraquinone-2,6-disulfonate revealed their enhanced resistance to fouling. All in all, heteroepitaxial SC-BDD represents a highly attractive electrode material which can, owing to the fabrication strategy, easily overcome size limitation, currently preventing broader use of single crystal diamond electrodes in electrochemical applications. [Display omitted] • First report on heavily B-doped (>1021 cm−3) heteroepitaxial diamond as an electrode. • Excellent electrochemical features of heteroepitaxial SC-BDD confirmed. • Only minor effect of variations in morphology on electrode performance recognized. • Anti-fouling characteristics of heteroepitaxial SC-BDD successfully demonstrated. • Heteroepitaxy approach enables synthesis of large-area SC-BDD electrodes. [ABSTRACT FROM AUTHOR]