Photo-responsive Doped 3D-printed Copper Electrodes for Water Splitting: Refractory One-pot Doping Dramatically Enhances the Performance

3D-printed electrochemical systems and devices are highly interesting due to their customizability and point-of-need fabrication capabilities. The most common and accessible fused deposition modeling (FDM) often requires modification of the resulting material, usually by atomic layer deposition or electrodeposition. We show doping of FDM-printed copper electrodes with metal oxide crystals via a one-pot preparation step. We will show that such doped materials have dramatically enhanced photoelectrochemical properties. We utilize the fact that the copper/polylactic acid filament requires the sintering of 3D-printed parts as a post-printing procedure to form electrically conductive devices useful for electrochemical applications. Thermally stable refractory materials (i.e., graphite or Al₂O₃) are mandatory for the sintering process to support the 3D-printed structure. Such refractory materials can dope the surface of the 3D-printed electrode in a one-pot process. For example, here, the Al₂O₃ microcrystals dramatically affect the measured photocurrents and the performance of the photoelectrodes. The detailed investigation using scanning photoelectrochemical microscopy to image electro- and photoelectrochemical-generated H₂ and O₂ offers spatially resolved information about the photoelectrochemical activity. Therefore, the presented work will have profound implications for the design and fabrication of metal-based electrochemical and photoelectrochemical 3D-printed devices because the doping method can be transferred to other metals and refractory materials.