A strategic framework for zinc oxide electrochemical synthesis using design of experiments

Electrochemical methods have gained increasing attention for the synthesis of micro- and nanostructured materials such as zinc oxide (ZnO). Traditionally, the development of such syntheses has relied on the One Variable At a Time (OVAT) approach, which systematically changes a single parameter while keeping others constant. However, this method provides only a limited understanding of the multidimensional experimental space. In contrast, a Design of Experiments (DoE) strategy offers a more efficient and statistically robust framework for identifying optimal synthesis conditions. In this work, we propose the application of a Full Factorial Design combined with Response Surface Methodology (RSM) to optimize for the first time the electrochemical synthesis of ZnO structures. The synthetic strategy integrates a hybrid electrochemical–Thermal process: sacrificial zinc electrolysis in a 30 mM sodium hydrogen carbonate solution, followed by thermal annealing that is typically employed in sol–gel methods to gain a final control over stoichiometry and morphology. ZnO microrods (ZnO MRs) were synthesized under galvanostatic conditions using benzalkonium chloride as a cationic surfactant and stabilizer. Its concentration (0.001–0.5 M) and the applied current density (2–20 mA/cm2) were selected as the key variables. A two-factor, three-level Central Composite Design (CCD) was implemented to investigate their combined effects on the electrosynthesis yield and ZnO length. The predictive model derived from the chemometric analysis was successfully validated, demonstrating the method’s potential for rational and efficient optimization of nano- and micromaterial electrosynthesis. Moreover, the proposed model was also validated on a scaled-up system, proving effective not only for laboratory-scale optimization but also for guiding process development toward industrial applications, where control, reproducibility, and efficiency are critical.