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Highly efficient and robust electrocatalysts intended for the oxygen evolution reaction (OER) are essential for energy conversion devices; the structural and morphological fractions of the electrocatalyst can also greatly influence the OER performance. Therefore, developing a high-performing electrocatalyst with desired properties is crucial through a simple and cost-effective chemical process. So, the binder-free, hydrous cobalt phosphate (Co3(PO4)2.nH2O) thin film electrocatalysts are prepared via the successive ionic layer adsorption and reaction (SILAR) method onto stainless steel (SS) substrates at ambient temperature. Additionally, the impact of annealing on the OER efficiency of thin film electrodes made of hydrous cobalt phosphate was observed by subjecting the electrocatalysts to different temperatures (200°C and 400°C). The SILAR synthesized hydrous Co3(PO4)2.nH2O with the short-range ordered agglomerated particles transformed into discrete nanoparticles with an annealing temperature. The as-prepared hydrous cobalt phosphate (CP) demonstrated outstanding OER performance with the least overpotential (η) of 265 mV at 10 mA cm-2 current density and the lowest Tafel slope of 37 mV dec-1, and the overpotential ( η 10 ) increased upon the annealing of catalysts (CP 200 and CP 400). Moreover, the as-prepared electrocatalyst demonstrated overall water splitting at the lowest potential of 1.56 V (@10 mA cm-2) in the alkaline electrolysis system (CP//Pt). The present study reveals that the electrocatalytic performance of the as-prepared cobalt phosphate thin film catalyst is significantly associated with the hydrous content present in catalysts and demonstrates the practical applicability of SILAR-synthesized binder-free cobalt phosphate thin film electrocatalysts. [ABSTRACT FROM AUTHOR]

To achieve higher supercapacitive performance of active material, several materials with precise structures and properties have been prepared using different chemical synthesis methods. Recently, amorphous materials are gaining much attention as an electrode in supercapacitor application as it provides superior electrochemical properties due to disorder in structure. So, in this investigation, a facile, binder free successive ionic layer adsorption and reaction (SILAR) method is adopted for the preparation and deposition of amorphous, hydrous nickel phosphate thin films on stainless steel substrates. The amorphous nickel phosphate shows mesoporous, clusters of particles like morphology. In the electrochemical study, the amorphous, hydrous nickel phosphate electrode demonstrates a superior specific capacitance of 1700 F g−1 (specific capacity- 814 C g−1) at 0.5 mA cm−2 current density along with excellent capacitive retention (96.55%) and coulombic efficiency (98.62%) over 5000 cycles. Furthermore, fabricated hybrid supercapacitor device using the nickel phosphate as cathode and reduced graphene oxide as anode exhibits specific capacitance of 113.5 F g−1 at 3 mA cm−2 current density with a high 40.37 Wh kg−1 energy density at 1.689 kW kg−1 power density alongwith excellent cyclic stability (95.09% retention after 5000 cycles). The obtained results illustrate that the amorphous, hydrous nature of nickel phosphate is a beneficial and superior choice as a cathode material in high-performing hybrid asymmetric supercapacitor devices. • A facile, binder free SILAR method used for deposition of amorphous, hydrous nickel phosphate thin films on SS substrates. • The prepared electrode shows specific capacitance of (814 C g-1) 1700 F g-1 with 96.5 % cyclic stability over 5000 cycles. • AHASD device offers 113.5 F g-1 specific capacitance with 40.37 Wh kg-1 energy density at 1.689 kW kg-1 power density. [ABSTRACT FROM AUTHOR]