Electrocatalytic water oxidation over AlFe₂B₂

We report excellent electrocatalytic performance by AlFe₂B₂ 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 AlFe₂B₂ and the formation of Fe₃O₄ nanoclusters on the exposed [Fe₂B₂] layers. Thus, the AlFe₂B₂ 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 AlFe₂B₂-supported Fe₃O₄ nanoclusters substantially exceeds the results obtained with unsupported nanoparticles of Fe₃O₄, FeB, or such benchmark OER catalysts as IrO₂ or RuO₂. The excellent catalytic performance and long-term stability of this system suggests that AlFe₂B₂ can serve as a promising and inexpensive OER electrocatalyst.