Hydrothermal Synthesis in Gap: Conformal Deposition of Textured Hematite Thin Films for Efficient Photoelectrochemical Water Splitting.

Obtaining high performance of hematite (α-Fe2O3) in a photoelectrochemical (PEC) water splitting cell is a challenging task because of its poor electrical conductivity and extremely short carrier lifetime. Here, we introduce a new hydrothermal method, called gap hydrothermal synthesis (GAP-HS), to obtain textured hematite thin films with an outstanding PEC water oxidation performance. GAP-HS proceeds in a precursor-solution-filled narrow gap to induce an anisotropic ion supply. This gives rise to an interesting phenomenon associated with the growth of nanomaterials that reflect the texture of the used substrates. Also, GAP-HS causes the preferential growth of hematite crystal along the [110] direction, leading to improved electrical conductivity within the (001) basal plane. The hematite thin films obtained via GAP-HS exhibit a very high photocurrent of more than 1.3 mA cm-2 at 1.23 V with respect to the reversible hydrogen electrode with 550 °C annealing only. It is the highest photocurrent, to the best of our knowledge, obtained for the hydrothermally synthesized pristine hematite photoanode. Because the low-temperature annealing allows avoiding of substrate deformation, the hematite thin films obtained via GAP-HS are expected to be advantageous for tandem-cell configuration.

Fabrication of Soft Sensor Using Laser Processing Techniques: For the Alternative 3D Printing Process.

Recently, the rapid prototyping process was actively studied in industry and academia. The rapid prototyping process has various advantages such as a rapid processing speed, high processing freedom, high efficiency, and eco-friendly process compared to the conventional etching process. However, in general, it is difficult to directly apply to the fabrication of electric devices, as the molding made by the rapid prototyping process is usually a nonconductive polymer. Even when a conductive material is used for the rapid prototyping process, the molding is made by a single material; thus, its application is limited. In this study, we introduce a simple alternative process for the fabrication of a soft sensor using laser processing techniques. The UV laser curing of polymer resin and laser welding of nanowires are conducted and analyzed. Through the laser processing techniques, we can easily fabricate soft sensors, which is considered an alternative 3D printing process for the fabrication of soft sensors.