Electrophoretic deposition of materials using humic acid as a dispersant and film forming agent

Electrophoretic deposition (EPD) method has been developed for the deposition of humic acid (HA) from solutions in water or mixed water–ethanol solvent. The deposition mechanism was based on the electrophoresis of anionic HA species, local pH decrease at the anode, charge neutralization and HA precipitation. The deposition yield can be varied by the variation of HA concentration and deposition voltage. HA showed remarkable adsorption on various materials, which involved different adsorption mechanisms. HA was used as a dispersing, charging and film forming agent for the EPD of materials of different types, such as oxide nanoparticles of TiO2 and MnO2, mineral particles of halloysite nanotubes and huntite platelets, metal nanoparticles of Ni and Pd, and other materials, such as SiC and multiwalled carbon nanotubes (MWCNT). The use of HA as a co-dispersant allowed for the fabrication of MnO2–MWCNT composites with various MWCNT content. The obtained films can be used for different applications based on the functional properties of the deposited materials, such as catalytic, flame retardant, molecular storage and electronic properties. Testing results showed promising performance of MnO2–MWCNT composites for applications in the electrodes of electrochemical supercapacitors.