Abstract

The electron transfer that occurs in the insertion of potassium in CuFeS2 has been analyzed by two different techniques. The binding energies of the core electrons of CuFeS2, KCuFeS2 and KxCuFeS2 (x ? 0) has been studied by XPS experiments, while the band structure of these phases has been investigated by tight-binding EH calculations. Both experimental and numerical results strongly support the belief that the insertion reaction induces a redox process in the starting CuFeS2, by which the Fe3+ ions are reduced to Fe2+. Upon removal of the potassium ions, the Fe2+ ions are oxidized to Fe3+. Copper atoms do not participate in the redox reaction.