Taguchi orthogonal design-based parametric tuning of nickel titanate for photocatalytic CO2 reduction in a microfluidic platform

In this work, NiTiO 3 was synthesized using a Taguchi L9 experimental design, forming the orthogonal matrix with parameters including reaction time, synthesis temperature, and calcination temperature. In response to the design, the bandgap value was selected and calculated by using Tauc plot method. The effect of the parameters in the experiments was studied, confirming that the calcination temperature at 600 ºC directly affects the formation of the phase. Another variable that affected its properties was the synthesis time, where time intervals of 6, 8 and 12 h resulted in similar bandgap values. Based on the 9 experimental parametric designs, ranging from L-1 to L-9, the synthesis conditions of experiment L-7 resulted in desired phase of the semiconductor and the nanomaterial was further used to develop working electrodes to explore its photoelectrochemical properties. By applying chronoamperometry (CA), the photocurrent density ( j ) was explored at potentials of -0.2, -0.4, -0.6 and, -0.8 V, from which -0.4 V was selected as the potential where j is stable. Open circuit potential (OCP) analysis revealed that NiTiO 3 is stable under visible light and is an n-type material. Mott-Schottky analysis was used to calculate the flat band potential of the material in an alkaline medium (0.1 M NaOH) which was found to be around (-1.17 eV vs. NHE). Finally, the photocatalytic evaluation of the material was carried out in a continuous flow microfluidic system using a flow rate of 50 μL/min, where ethanol was CO 2 reduction (CO2R) product.