Three-Dimensional Mn-Substituted CuCo₂S₄-MWCNT for Electrocatalytic Oxidation of Glycerol

Given its cost-effectiveness and favorable electrochemical properties, Cu-Co spinel sulfide was selected as the electrode material for an in-depth investigation. The Mn-substituted CuCo₂S₄-multiwalled carbon nanotube (MWCNT) composite was then synthesized via a solvothermal approach, targeting the electrocatalytic oxidation of glycerol. Physical and electrochemical characterizations revealed that the CuCo_0.5Mn_1.5S₄-MWCNT composite demonstrated a superior catalytic performance. This was evidenced by its low overpotential, reduced electrochemical impedance (17.8 Ω), and smaller Tafel slope (60 mV dec^-1), along with good long-term stability (retention rate of 73%) and tolerance under operational conditions. The enhanced performance of the CuCo_0.5Mn_1.5S₄-MWCNT composite is likely attributed to Mn ion substitution. This substitution not only elevates the relative surface concentration of Co³⁺ and Mn³⁺ in the sulfur spinel structure but also increases the O_ads/O_latt ratio to 1.2. Density functional theory (DFT) calculations further support that Mn substitution significantly boosts the electrical conductivity of the composite. Moreover, the integration of highly conductive MWCNTs as a structural framework results in a stable 3D architecture within the CuCo_0.5Mn_1.5S₄-MWCNT composite. This research presents a promising strategy for electrocatalytic glycerol oxidation, leveraging hybrid materials composed of transition-metal sulfides and carbonaceous substrates as conductive platforms.