Residual Porosity of 3D‐LAM‐Printed Stainless‐Steel Electrodes Allows Galvanic Exchange Platinisation

Abstract

Stainless‐steel rods were manufactured by laser additive manufacturing (LAM or “3D‐printing”) from a stainless‐steel (316 L) powder precursor, and then investigated and compared to conventional stainless steel in electrochemical experiments. The LAM method used in this study was based on “powder bed fusion”, in which particles with an average diameter of 20–40 μm are fused to give stainless‐steel rods of 3 mm diameter. In contrast to conventional bulk stainless‐steel (316 L) electrodes, for 3D‐printed electrodes, small crevices in the surface provide residual porosity. Voltammetric features observed for the 3D‐printed electrodes immersed in aqueous phosphate buffer are consistent with those for conventional bulk stainless steel (316 L). Two chemically reversible surface processes were observed and tentatively attributed to Fe(II/III) phosphate and Cr(II/III) phosphate. Galvanic exchange is shown to allow improved platinum growth/adhesion onto the slightly porous 3D‐printed stainless‐steel surface, resulting in a mechanically robust and highly active porous platinum deposit with good catalytic activity toward methanol oxidation.

Galvanic exchange platinization reveals laser-inscribed pattern in 3D-LAM-printed steel

“…Comparison of galvanic exchange reactivity of conventional and 3D-printed steel It has recently been shown [12] that platinum catalyst coatings are formed on both conventional steel (with poor adhesion) and 3D-printed steel (with good adhesion) when exposed to a solution of PtCl 6 2− in aqueous HCl. The process is consistent with galvanic exchange [20] and formally expressed in Eq.…”

“…The 3D-printed steel rods were prepared from SS 316 L powder (EOS GmbH -Electro Optical Systems, Robert-StirlingRing 1, D-82152 Krailling, München) at Lappeenranta University of Technology in Finland as reported previously [12]. Briefly, a powder of steel with typically 20-μm diameter is layered over the sample surface and then laser sintered.…”

“…5c, d). It has recently been proposed that much more substantial platinum deposits on 3D-printed steel show promising reactivity [12]. Figure 6a shows current density data (experimental data was scaled to 1-cm 2 -geometric surface area) for cyclic voltammograms obtained at a scan rate of 50 mVs −1…”

“…Like conventional steel, the surface of 3D-printed steel is typically covered with a protective oxide layer, but this can be breached in aqueous HCl media, resulting in hydrogen evolution or metal dissolution and/or deposition processes. Recently, we have shown that 3D-printed steel surfaces are readily modified with platinum catalysts in a simple galvanic exchange process [12]. Compared to other types of platinum deposition (sputtering [13], focused ion beam deposition [14], thermolytic deposition [15], or atomic layer deposition [16]), galvanic exchange is practical and efficient [17].…”

“…When testing the electrodes produced by galvanic exchange platinization, it was observed that the electrocatalytic performance towards methanol oxidation (in acidic media) was improved relative to that for similar platinum nano-materials. The effect was attributed to iron (and possibly other) impurities becoming incorporated into the galvanically exchanged platinum catalyst to promote the catalytic activity [12,18,19].…”