Facile One-pot Hydrothermal Synthesis and Characterizations of Cobalt Selenide Nano Particles for Oxygen Evolution Reaction [OER]

Abstract

Controllable and facile fabrication of an efficient and durable catalysts for water splitting is research field of immense importance. Owing to slow and complex sluggish kinetics of oxygen evolution reaction (OER) of water splitting, engineering an economical and stable material is a challenging task. Low over potential, high current density, and high stability are the three most imperative deciding factors of an ideal catalyst for OER.keeping in view of all these factors, an industrious, efficacious and effective catalysts were designed in this study. In the first scheme, Cobalt selenide nano-composite was synthesized by simple facile one-pot hydrothermal method followed by different optimizations factors such as sodium dodecyle Sulfate (SDS) concentration, reaction time and temperature. In the second study, rational optimizations of SDS concentration and reaction temperature were considered in the synthesis of [NiCo2O4] nano-composite. The as-synthesized materials were characterized using X-ray diffraction technique(XRD), Scanning Electron Microscopy (SEM), Energy Dispersive spectroscopy (EDX), and Raman spectroscopy. It was found that highly crystalline CoSe and [NiCo2O4] were synthesized and its crystallinity varied with different factors. These materials were then employed for electro catalytic water splitting particularly oxygen evolution reaction. In basic media, both CoSe and [NiCo2O4] nano composites exhibited phenomenal electrochemical response. In case of CoSe synthesized at 180 with 0.5 gm of SDS and 16 hour of reaction time interval, manifested highest current density of 570 mA cmð€€€2 at 1.54 V with onset potential of 1.48 V vs Reverse Hydrogen Electrode (RHE). The over potential for a 10 mA of current was found 250 mV, with a least tafel slope of 56 mV decð€€€1, and high electrochemically active surface area ECASA of 1103 cm2 and least charge transfer resistance of only 0:218. Stability and durability was checked at 20 mA and 50 mA for 24 hours and found highly stable with minimal decay in current density and rise in over potential. Similarly, [NiCo2O4] synthesized with 1 gm of SDS and at 100 reaction temperature reflected exceptional results. [NiCo2O4] exhibited current density of 658 mA cmð€€€2 at 1.62 V with onset potential of 1.55 V vs Reverse Hydrogen Electrode (RHE). The over potential for 50 mAcmð€€€2 and 100 mAcmð€€€2 current density was found 370 mV and 400 mV, with least tafel slope of 90 mv decð€€€1, and high electrochemically active surface area ECASA of 2130 cm2 and least charge transfer resistance of only 1.3 ohm. Stability and durability was checked at 20 mA and 50 mA for 10 hours and no significant degradation was observed. In a nutshell, the as-synthesized catalysts can be used in commercial and industrial scale to meet the rising energy need.