Metal-reduction-induced changes in the paramagnetic properties and the rate of oxygen and hydrogen exchange in copper-containing coal-tar carbon fibers

Abstract

Changes in the binding of copper to a carbon matrix during the reduction of Cu2+ ions to metallic state (Cu0) influence the EPR spectra of unpaired electrons and the rate of hydrogen (H2) and oxygen (O2) exchange in coal-tar carbon fibers (CFs) with copper chloride (CuCl2 · 2H2O) deposited from solution. In the presence of the carbon matrix, Cu2+ ions are reduced to Cu0 by H2 at a lower temperature (150°C) than in a pure copper salt. The Cu2+ → Cu0 transition on the CF surface is accompanied by changes in the EPR spectra of unpaired electrons (g value, linewidth, saturation of resonance transitions). The binding of H2 to the CF-Cu0 surface becomes stronger and the rate of H2 displacement by O2 from the pores decreases and becomes equal to the rate of O2 displacement by H2.