Discharge-ionization of hydrogen on modified carbon nanotube electrodes

Discharge-ionization of hydrogen on carbon nanotube (CNT) electrodes in H3PO4 aqueous solution has been investigated and the effect of catalysts (Pt and polynuclear complexes 2Co–Ni with aminoethanol ligands) has been studied. It was found that the most probable mechanism contains the slow step of hydrogen atoms recombination on highly energetically nonuniform surface of CNT when the polarization is low. Increasing the polarization for more than −300 to −350 mV vs silver chloride reference electrode results in the operation of the CNT as a porous gas electrode with linear current-potential dependence. The influence of catalysts consists in the, first, decrease of the ohmic resistance of this electrode and, second, increase of the coulomb efficiency of charge (reduction of H+ ions) to discharge (oxidation of stored H2) from 70 to 80–90%. As follows from the results, the complexes 2Co–Ni can be used instead of Pt in the CNT-based hydrogen storage materials.

► Discharge-ionization of hydrogen on CNT electrodes in H3PO4 solutions. ► The hydrogen atoms recombination is the rate determining step. ► The catalytic effects of Pt and 2Co–Ni aminoethanol complex have been studied. ► Both catalysts decrease the resistance and increase the efficiency of the process. ► 2Co–Ni aminoethanol complex can be used instead of Pt as the catalyst.