Framework for additive manufacturing of porous Inconel 718 for electrochemical applications

Porous electrodes were developed using laser powder bed fusion of Inconel 718 lattice structures and electrodeposition of a porous nickel catalytic layer. Laser energy densities of ∼83–333 J/m were used to fabricate ∼ 500 µm thick electrodes made of body centered cubic unit cells of 200–500 µm and strut thicknesses of 100–200 µm. Unit cells of 500 µm and strut thickness of 200 µm were identified as optimum. Despite small changes in feature sizes by the energy input, the porosity of >50 % and pore size of ∼ 100 µm did not change. In a subsequent step, we used nickel electrodeposition to create smaller scale pores on the electrode. The electrochemical performance of the electrodes for hydrogen/oxygen evolution reaction (HER/OER) was evaluated in a three-electrode setup. For HER, a much larger maximum current density of ∼−372 mA/cm² at a less negative potential of ∼−0.4 V vs RHE (potential against reversible hydrogen electrode) was obtained in the nickel-coated samples, as compared to −240 mA/cm² at ∼−0.6 V in the bare ones, indicating superior performance of the coated samples. Conversely, OER exhibited minor performance differences upon application of the coating, indicating insignificant dependence of OER to surface composition and available surface.