Unusual redox activity of composite alkaline earth metal oxides and reduced graphene oxide system

Abstract

Reduced graphene oxide (rGO) impregnated on Group 2 alkaline earth oxides (CaO, SrO, BaO) matrix following mechanical mixing, thermal annealing and subsequent cold shock has yielded a new electrochemical material. Material characterization has been done by Fourier transform infrared spectroscopy, scanning electron microscopy and powder X-ray diffraction patterns in micrometer dimension. Thermal stability has been checked by thermal gravimetric analysis and differential scanning calorimetry. Cyclic voltammetry of the composites shows anodic peak potential in the order –0.6 V (rGO-CaO) < –0.4 V (rGO-SrO) < –0.3 V (rGO-BaO), which also follows the ordering of ionic size, Ca²⁺ (100 pm) < Sr²⁺ (118 pm) < Ba²⁺ (135 pm). They exhibit unexpected inherent redox activity with an amazing chemical reversibility. This characteristic becomes more prominent on moving down the group. Thermal stability of these coupled systems also increases down the group.