Experimental research using monocrystalline electrodes has been a hallmark of interfacial electrochemistry and electrocatalysis since 1980. However, it has been limited to mainly noble metals because of the challenges encountered when using non-noble metals. We report on the development of controlled-atmosphere flame fusion that enables the growth of spherical single crystals of non-noble metals in controlled gaseous atmosphere and without the formation of surface or bulk oxides. The set-up is used to grow nickel single crystals the structure of which is verified using Laue X-ray back-scattering and scanning electron microscopy (SEM). The equilibrium shape of the nickel single crystals calculated using Wulff construction agrees with the actual shape determined using SEM. Electrochemical measurements in aqueous NaOH solution using the monocrystalline Ni electrodes reveal cyclic voltammetry features unique to their surface structure. The methodology, transferrable to other metals, creates enormous research opportunities in interfacial electrochemistry, electrocatalysis, surface science, gas-phase catalysis, and corrosion science.