Cobalt pyrophosphate (Co2P2O7) derived from an open-framework cobalt phosphite: a durable electroactive material for electrochemical energy conversion and storage application

Abstract

Water splitting is a sustainable method of qualitative as well as quantitative oxygen production to support future energy conversion systems and strictly depends on the nature of the electrocatalyst. Likewise, electrochemical energy storage systems particularly supercapacitors are of importance for future sustainability. Therefore, finding an efficient high-performance electrode material with both electrocatalytic activity and electrochemical energy storage capacity remains an emerging task for sustainability. In view of this challenge, we have derived a composite of partially graphitized carbon with Co₂P₂O₇ (GC-CPP), a non-noble metal, low-cost electroactive material from open-framework cobalt phosphite. The crystal structure, surface morphology and elemental composition of the sample have been analyzed using PXRD, Raman, FESEM, HRTEM and X-ray photoelectron spectroscopy. More importantly, the electrochemical performances have been assessed using cyclic voltammetry, linear sweep voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopic methods. In alkaline electrolyte, GC-CPP catalyzes the OER requiring only 165 mV overpotential to reach 10 mA cm⁻² current density with lower Tafel slope (41 mV dec⁻¹). When used as an anode for a supercapacitor, GC-CPP shows higher specific capacitance (900 F g⁻¹) compared to the pyrophosphates studied to date. Further, the high values of energy (31.25 W h kg⁻¹) and power densities (21 kW kg⁻¹) and cyclic durability prove the suitability for practical application. This strategy of deriving highly active electrode material from open frameworks provides an opportunity to design efficient and cost-effective electrode material for renewable energy technologies.