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Nowadays, electrochemical water splitting is a securing alternative for clean-energy production and also an efficient expertise for oxygen and hydrogen production. Compared to single metal-based electrocatalyst, multi metal-based electrocatalyst offers more active sites, high surface area, and distinctive nanostructure for effective water oxidation. In this work, nickel and cobalt co-doped MnCO 3 was successfully synthesized via a facile co-precipitation technique. Rhombohedral crystal phase of MnCO 3 nanostructures and its crystallite sizes were thoroughly analyzed by the XRD spectra. Incorporation of doping element such as Ni and Co in MnCO 3 nanostructures exhibited two different morphologies which enhanced the catalytic performance of the prepared samples. Large surface area and porosity of the nanomaterials improved the stability and activity of the prepared MnCO 3 nanostructures. EDX analysis confirmed Mn, C, O, Ni and Co elements in stoichometric ratio. Moreover, the specific capacitance of (Ni, Co) co-doped MnCO 3 nanostructures attained 581 F/g while the other electrodes attained only 207, 332 and 175 F/g respectively. A small Tafel slope with low overpotential of Ni, Co co-doped MnCO 3 nanostructures was 20.2 mV/dec and 293 mV respectively. Therefore, the prepared electrocatalysts of Ni, Co co-doped MnCO 3 nanostructure is one of the attractive anode material for high performance energy conversion applications. • Ni, Co co-doped MnCO 3 attained 581 F/g while others attained 207, 332 and 175 F/g. • Ni, Co co-doped MnCO 3 explored low 293 mV overpotential. • Ni, Co co-doped MnCO 3 is attractive anode for high performance energy conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • CW1, CW2 and CW3 electrodes overpotential were 123, 115 and 102 mV. • Tafel slope values of prepared electrodes were 245, 244 and 238 mV/dec. • CW3 electrode exhibited high C dl value of 32.8 mF/cm2 and enhanced HER. • CW3 electrode exhibited 75% retention in 16 h durability test. Hexamethylenetetramine (HMT) assisted calcium tungstate nanostructures were successfully synthesized through co-precipitation method. The phase and material confirmation of scheelite type calcium tungstate nanostructures with tetragonal unit cell (a = 5.193 and c = 11.255) were done by employing X-ray diffraction (XRD). All the prepared electrocatalysts such as CW1, CW2 and CW3 crystallite sizes were 29.01, 24.86 and 17.40 nm respectively. The calculated band gap values were found to be 3.31, 3.31 and 3.27 eV for CW1, CW2 and CW3 materials respectively. Different morphology such as ball like and dumbbell shaped calcium tungstate were revealed by scanning electron microscopy (SEM). Surfactant largely plays a significant role to reduce nanostructures agglomeration. The specific surface area, pore volume and diameter of 0.1 M hexamethylenetetramine (HMT) assisted calcium tungstate nanostructure was about 24.7 m2/g, 0.141 cc/g and 3.365 nm. The surface area of the calcium tungstate nanostructures drastically enhanced hydrogen evolution reaction (HER) performance as recognized by linear sweep voltammetry. The overpotential values of CW1, CW2 and CW3 electrodes were 123, 115 and 102 mV respectively. Solution resistance (R s) and charge transfer resistance (R ct) of synthesized materials was finding out by electrochemical impedance spectroscopy and all prepared electrocatalyst estimated values were 1.07, 1.25, 1.34 Ω and 4.06, 1.62, 0.76 Ω respectively. The stability of 0.1 M hexamethylenetetramine (HMT) assisted CaWO 4 was analyzed by 16 h and it exhibited excellent robustness without any decay. The synthesized CaWO 4 material exhibited superior hydrogen evolution reaction (HER) activity and the prepared electrodes was capable electro catalysts in water splitting applications. [ABSTRACT FROM AUTHOR]