Studying plasma in-liquids has received increasing scientific interest over the last two decades for its possible application in, e.g., wastewater treatment, nanoparticle formation, 2,4,6-13 catalyst material preparation, 14,15 plasma electrolytic oxidation, or plasma electrolytic polishing. These investigations provide information on the modification of the plasma electrode or changes induced within the electrolyte. Gas-phase plasma can be used in a similar way to modify the plasma electrode or the properties of a substrate placed close to the plasma source. Related to catalytic applications, the gas-phase plasma can also be used, e.g., to change the mechanism of a catalytic reaction on the target (gas-phase plasma catalysis) or to tailor the structural properties of the target, for example, to form catalyst materials with distinct (electro)catalytic properties. In contrast, much less is known about the effect of in-liquid plasma on target materials.