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We report excellent electrocatalytic performance by AlFe 2 B 2 in the oxygen-evolution reaction (OER). The inexpensive catalytic material, prepared simply by arc-melting followed by ball-milling, exhibits high stability and sustained catalytic performance under alkaline conditions. The overpotential value of 0.24 V observed at the current density of 10 mA cm -2 remained constant for at least 10 days. Electron microscopy and electron energy loss spectroscopy performed on the initial ball-milled material and on the material activated under electrocatalytic conditions suggest that the catalytic mechanism involves partial leaching of Al from the layered structure of AlFe 2 B 2 and the formation of Fe 3 O 4 nanoclusters on the exposed [Fe 2 B 2 ] layers. Thus, the AlFe 2 B 2 structure serves as a robust supporting material and, more importantly, as a pre-catalyst to the in situ formed active electrocatalytic sites. Comparative electrochemical measurements demonstrate that the electrocatalytic performance of the AlFe 2 B 2 -supported Fe 3 O 4 nanoclusters substantially exceeds the results obtained with unsupported nanoparticles of Fe 3 O 4 , FeB, or such benchmark OER catalysts as IrO 2 or RuO 2 . The excellent catalytic performance and long-term stability of this system suggests that AlFe 2 B 2 can serve as a promising and inexpensive OER electrocatalyst.