## 3 Results and Discussion
### 316L Stainless Steel Electrodes for Oxyhydrogen Gas Production  
#### 3.1.1 HHO Gas Flow Rate  
Reducing the electrode spacing and increasing the operating temperature can enhance energy efficiency in water electrolysis. Elevated temperatures improve reaction kinetics by altering the physicochemical properties of water. Specifically, heating decreases water's dielectric constant, surface tension, and viscosity while increasing the concentration of OH\({}^{-}\) and H\({}^{+}\) ions. Additionally, as temperature rises, the voltage required to overcome the Helmholtz energy barrier decreases, thereby lowering the electrical potential necessary for hydrogen gas production, as previously reported [4; 10]. Based on these principles, a 15 mm electrode spacing and an operating temperature of 80 \({}^{\circ}\)C were selected for the current electrolyzer setup to optimize HHO gas production. In this study, HHO gas flow rate measurements were conducted 10 min after power activation, in 5 min of water electrolysis at 80 \({}^{\circ}\)C and at constant currents of 6A, 7A, and 8A. Figure 6 presents the HHO gas production rates (mL) at different current levels using various electrode materials. Results indicate that increasing the current from 6A to 8A enhances HHO gas production across all electrode types. This is attributed to the higher current providing a greater number of electrons available for electrochemical reactions, thereby increasing the overall reaction rate and improving hydrogen generation efficiency. At 6A, the as-rolled electrode exhibited the lowest HHO gas flow rate at 89 mL, followed by the as-built electrode at 110 mL. The HT1 electrode produced 132 mL, while the HT2 electrode generated 135 mL of HHO gas. At 7A, HHO production increased across all electrode conditions. The as-rolled electrode produced 120 mL, the as-built specimen generated 137 mL, the HT1 electrode yielded 160 mL, and the HT2 electrode produced 174 mL. At 8A, this trend continued, with the as-rolled electrode producing 138 mL, the as-built electrode generating 170 mL, the HT1 electrode yielding 210 mL, and the HT2 electrode generating 205 mL of HHO gas. The variations in HHO production rates can be attributed to differences in material microstructure. The as-rolled electrode, serving as the baseline material, exhibited lower HHO production rates due to its fewer catalytic active sites and a less favorable microstructure for electrolysis. In contrast, the AM electrodes demonstrated higher HHO production rates compared to the as-rolled electrode, suggesting that the additive manufacturing process introduces structural modifications that enhance catalytic activity. The 3D printing process can generate a surface with increased defects and higher roughness, which in turn provides more catalytically active sites, thereby improving the efficiency of the electrolysis process. Post-processing heat treatment (PPHT) plays a crucial role in reducing grain boundary defects and increasing the material's uniformity. The uniform grain structure enhances  
Figure 6: HHO production rate at varying currents using different electrode materials. electrical conductivity and reduces resistance, thereby improving HHO production rates. HT1 (held at 800 \({}^{\circ}\)C for 20 min, air-cooled) likely reduces residual stresses from the 3D printing process and improves microstructural uniformity, leading to better electrochemical performance. HT2 (held at 1050 \({}^{\circ}\)C for 20 min, water-quenched) further enhances the microstructure and surface characteristics, optimizing both mechanical properties and catalytic activity. The improvement in HHO production at higher currents is more pronounced in post-heat-treated electrodes, indicating that an optimized microstructure and an increased active surface area significantly enhance catalytic efficiency. The HT2 electrodes exhibited the highest HHO production rates, suggesting an optimal balance between mechanical integrity and catalytic performance.