ADDITIVE MANUFACTURING OF METAL FOAMS AND THEIR APPLICATIONS IN THE GREEN ENERGY HARVESTING FIELD

Abstract

Metal foam is a class of lightweight cellular materials, which is inspired by nature. Owing to its unique properties, it has a very high potential in a wide range of applications such as energy absorption, sound-absorbing, heat exchanger, energy storage, and energy harvesting. Furthermore, to explore the enhancement of electrochemical properties of metal foams in the green energy harvesting field, surface functionalization by electroless/electrochemical deposition, and a new fabrication method via digital light processing to achieve high-resolution metal foams with complex structure design were introduced. In this thesis, NiFe bimetallic oxyhydroxide composites were fabricated on nickel foams by a mild electrochemical oxidation strategy to obtain robust and super wetting properties which are of great benefits for enhancement of oxygen evolution reaction (OER) performance. Subsequently, the incorporating of the sulfur element in NiFe oxyhydroxide nanostructures allows a further improvement on electron transfer and wetting performance, which results in an ultra-low overpotential of 260 mV to drive a 1 A/cm2 OER. Considering the practice usage, copper foams were selected and investigated for a low-cost OER due to their abundant existence as compared to nickel foams. Copper-cobalt-sulfur-oxygen nanowire coating on copper foam at room temperature was synthesized by a mild chemical plating strategy. Similarly, urea XVIII electrolysis can utilize such a system to solve urea-containing wastewater issues and produce green energy in the meanwhile. With the studies of metal foams with functional coatings for energy harvesting application, an imperative requirement for metal foam substrates is conscious of. Herein, one of the additive manufacturing methods, digital light processing (DLP) using metal precursors was introduced to produce various types of metal foams including nickel, copper, cobalt, silver, invar alloys, etc. A tunable, high-resolution, and designed structure of 3D printed metal foams were obtained. As-fabricated 3D metal foams were tested for OER and a low overpotential with high stability and the mechanical property was exhibited.