In this report, highly active hydrous cobalt phosphate thin film electro-catalysts were synthesized by a low cost and one-pot hydrothermal method at 393 K and were evaluated for the oxygen evolution reaction (OER). The impact of varying the hydrolyzing agent, urea, on the structural and morphological properties of hydrous cobalt phosphate thin films and the consequent electro-catalytic performances was studied. The morphology of hydrous cobalt phosphate thin films resembles a microflower-like structure consisting of microplates. Upon urea variation, the microplates undergo changes in thickness and width and eventually transform into microflakes. The remarkable electrocatalytic performance of hydrous cobalt phosphate thin films was observed towards the OER and they exhibit a low overpotential of 292 mV (vs. RHE) at 10 mA cm⁻² current density with a Tafel slope of 98 mV dec⁻¹ in 1.0 M KOH electrolyte. Also, the stability of the electrocatalyst is demonstrated by continued electrolysis, showing that the hydrous cobalt phosphate thin film electro-catalyst sustains superior long-term electrochemical stability for 10 h at 10 mA cm⁻² constant current density. The enhanced electrocatalytic performance of hydrous cobalt phosphate thin film electro-catalysts was attributed to a high ECSA (1210 cm⁻²) and low electrochemical impedance imparted by the microflower structure with microflake-like morphology.

A metal–organic framework (MOF) is a highly porous material with abundant redox capacitive sites for intercalation/de-intercalation of charges and, hence, is considered promising for electrode materials in supercapacitors. In addition, dopants can introduce defects and alter the electronic structure of the MOF, which can affect its surface reactivity and electrochemical properties. Herein, we report a copper-doped iron-based MOF (Cu@Fe-MOF/NF) thin film obtained via a simple drop-cast route on a 3D-nickel foam (NF) substrate for the supercapacitor application. The as-deposited Cu@Fe-MOF/NF electrodes exhibit a unique micro-sized bipyramidal structure composited with nanoparticles, revealing a high specific capacitance of 420.54 F g⁻¹ at 3 A g⁻¹ which is twice compared to the nano-cuboidal Fe-MOF/NF (210 F g⁻¹). Furthermore, the asymmetric solid-state (ASSSC) supercapacitor device, derived from the assembly of Cu@Fe-MOF/NFǁrGO/NF electrodes, demonstrates superior performance in terms of energy density (44.20 Wh.kg⁻¹) and electrochemical charge–discharge cycling durability with 88% capacitance retention after 5000 cycles. This work, thus, demonstrates a high potentiality of the Cu@Fe-MOF/NF film electrodes in electrochemical energy-storing devices.