Energy of activation(Ea), and thermodynamic parameters such
as enthalpy (ΔH#) and entropy(ΔS#) were determined by Arrhenius’s
equation and Eyring equation48 respectively. The value
of Gibbs free energy (ΔG#) was determined by the relation
as ΔG# = ΔH# - TΔS#
The activation energy(Ea) for catalyst Alg/CMC/Dex/MnO2/
g-C3N4/Ca is 21.56 kJ mol-1(Fig. S1) which confirms the
reduction reaction is slow and surface controlled on catalyst
surface. The value of enthalpy (ΔH#) is 7.46 kJmol-1(Fig.11)
suggests that the reaction needs energy. The value of Gibbs
free energy (ΔG#) increases from 56.352 to 59.634 kJmol-1
with increase of temperature confirmed that the reduction of
Cr(VI) to Cr(III) required energy.The value of entropy(ΔS#)
is -16.425Jmol-1K-1 at suggests that the reaction is feasible at
higher temperature. 49 The temperature coefficient is 1.158
& 1.113 attributing the reaction is favorable at higher scale
origin of plastic crystals with CBCEs and provides important
guidance to the design of next-generation solid-state refrigeration
technology for practical application. In the fabrication of
electrode, the composition of graphite powder, nanocomposite
with pasting liquid (paraffin oil) strongly affects the reactivity
of electrode. The increase in the amount of pasting liquid decreases
electron transfer rates as well as the background current
contributions.37-38 The optimum amount of Alg/
CMC/Dex/MnO2/g- C3N4/Ca nanocomposite mixed
with graphite powder to fabricate Alg/CMC/Dex/MnO2/
g-C3N4/Ca/CPE was achieved by varying the amount of Alg/
CMC/Dex/MnO2/g-C3N4/Ca from 5% to 20% (w/w) in
total paste material and their peak response were analysed by
recording differential pulse voltammogram (DPV) of 1.0×10-6
molL-1 K2Cr2O7 in acetate buffer pH 5.5. The best electrode
response was obtained with 15% (w/w) of nanocomposite
60% (w/w) graphite powder and 25% (w/w) paraffin oil.
Similarly in case of Alg/CMC/Dex/Ca/CPE and Alg/CMC/
Dex/MnO2/Ca/CPE, 15% (w/w) of Alg/CMC/Dex/Ca and
Alg/CMC/Dex/MnO2/Ca in total paste material shows the
best peak response for 1.0×10-6 mol L-1 K2Cr2O7.
