Nanoplates and Nanospheres of Co3(VO4)2 as Noble Metal-free Electrocatalysts for Oxygen Evolution

The Co3(VO4)2 multilayer nanoplates [Co3(VO4)2-MNs] and Co3(VO4)2 ultrafine particle-comprised nanospheres [Co3(VO4)2-UPNs] were prepared for the oxygen evolution reaction (OER). They are synthesized by a simple hydrothermal reaction using ethylenediaminetetraacetic acid and polyvinyl pyrrolidone as dispertants and pretectants. With the help of multi-walled carbon nanotubes (MWCNTs), the Co3(VO4)2-MNs and Co3(VO4)2-UPNs were immobilized respectivtly onto the surface of glassy carbon electrodes (GCEs). By comparison, the GCE-Co3(VO4)2-MN/MWCNT exhibits higher performance of OER electrocatalysis and better stablity than the GCE-Co3(VO4)2-UPN/MWCNT in the alkali electrolyte of 1 M KOH due to its higher surface roughness. The high surface free energy of Co3(VO4)2-MNs is helpful for their immobilization on elelctrode surface, leading a better stability. The work shows that the noble metal-free electrocatalysts can lower the energy barrier and improve the energy efficiency for electrochemical water splitting to generate hydrogen.