A TiO2/Pt based electrode exhibited better activity for the oxidation of coal in a basic system compared to Ti/Pt, TiO2–Cu/Pt and pure metal electrodes. The surface morphologies and composition of the electrodes were studied by SEM and XRD, respectively. Linear sweep voltammetry was employed to investigate the catalytic effects of electrodes, and the product of coal oxidization was determined by a gas collection test. The TiO2/Pt electrodes that were modified with NiO and/or Co3O4 exhibited higher average currents and a lower decrease in mass during electrolysis compared to the other electrodes; this finding indicated that NiO and Co3O4 play important roles as catalysts.Highlights► Electrodes based on porous TiO2/Pt substrate were employed for the electro-oxidation of coal in basic electrolyte system. ► TiO2/Pt electrodes modified with NiO and/or Co3O4 catalysts show great activity in the electro-oxidation of coal. ► Hydroxyl radical generated by the metal oxide plays important role in the reaction.

Electrocatalytic oxidation of coal on Ti-supported metal/metal oxides coupled with liquid catalysts is systematically investigated as a method of producing hydrogen at the cathode. The composition of the liquid catalyst was varied to determine its effect on the coal electrolysis. A spectrum of byproducts from the coal oxidation at the anode was analyzed. The Ti-supported metal oxide electrodes were prepared by thermal decomposition and characterized by scanning electron microscopy (SEM). X-ray diffraction results show that the composition of the electrodes was Ti/Pt, Ti/RuO2, Ti/IrO2 and Ti/IrO2–RuO2. Coal oxidation tests on these electrodes indicate that Ti/IrO2 has the best electrocatalytic activity. Polarization curves reveal that redox catalysts, such as Fe3+, K3Fe(CN)6, KBr and V2O5, bridge the coal particles and the solid electrode surface, thus increasing the rates of coal oxidation. The dynamic transition of Fe3+/Fe2+ is proven by a KMnO4 titration experiment, and the possible catalytic mechanism is discussed. Product analysis shows that pure H2 is generated at the cathode and that CO2 is the main product at the anode.

The electro-hydrogenation of coal on Pb electrode in a mixed dimethylformamide-ethanol (DMF-EtOH) electrolyte was investigated. The hydrogenation product was in-situ extracted from the organic solvent and characterized. The electrolysis products show a significant increase in H/C ratio, indicating increased hydrogenation efficiency. IR spectroscopy shows the reduction of C=O bond and aromatic ring, as well as the cleavage of bridge bonds, such as C-O-C, are the main reactions during the electrolysis. This is also confirmed by the increase of γ-H content measured by 1H-NMR.