Efficient Electrochemical Reconstruction of a Cobalt- and Silver-Based Precatalytic Oxalate Framework for Boosting the Alkaline Water Oxidation Performance
Suptish Ghosh, Suptish Ghosh, Ayan Mondal, Gouri Tudu, Sourav Ghosh, Sourav Ghosh, Heramba V. S. R. M. Koppisetti, Harish Reddy Inta, Dipannita Saha, Venkataramanan Mahalingam
Abstract
The quest toward finding an efficient oxygen evolution reaction (OER) catalyst utilizing a sustainable and facile synthetic strategy is still underway. Low overpotential, better stability, and rapid kinetics are the key features to be considered while designing a competent OER catalyst. Herein, we have developed a rapid and efficient wet chemical route for the synthesis of a cobalt- and silver- based precatalytic oxalate (CoC2O4/Ag2C2O4) framework via a rapid precipitation method at room temperature. The optimized catalyst required an overpotential of 260 mV to reach the benchmark current density of 10 mA/cm2geo, with a Tafel slope value of 47 mV/dec. It has also shown 72 h of chronopotentiometry stability as well as 1000 cycles of potentiodynamic stability along with 90% Faradaic efficiency in 1(M) KOH for OER. Addition of a minimal amount of silver component assists in the reduction of overpotential up to 120 mV compared to CoC2O4. Furthermore, the minimal amount of silver inclusion improved the charge migration property via lowering the charge-transfer resistance besides tuning the charge storage mechanism (b value). The paradigm shift in catalytic efficiency can be manifested by calculating both intrinsic (per-site activity) and geometric (based on the effective area of electrode materials) activities. Interestingly, significant improvement in Cdl (double-layer capacitance) from 10.25 to 19.59 mF/cm2 is achieved upon silver component inclusion, indicating a higher number of accessible catalytic sites for alkaline OER. The turnover frequency value further authenticates the importance of silver component in the precatalytic oxalate network for intrinsic catalytic activity under alkaline conditions. The mechanistic trajectory is also investigated from the proton reaction order (ρRHE), revealing the occurrence of the proton-decoupled electron transfer process for the optimized catalyst. The results reveal the efficient electrochemical surface reconstruction in the cobalt- and silver-based precatalytic oxalate framework for improved alkaline water oxidation through exposing the surface as well as bulk active centers for easy electrolyte diffusion in alkaline medium.