The growing demand for fossil fuels is causing a series of environmental issues, most notably global warming. Finding the next general energy carrier which can store intermittent energy provided by wind or the sun is a key challenge for mankind. One possible solution for overcoming these obstacles is electrocatalytic water splitting, which generates hydrogen as a promising “green” fuel. This thesis explores electrochemical water splitting, and deals with challenges relating to the design and fabrication of electrodes, the electrochemical activity of catalysts, and the connection between catalysts and conductive supports. As one solution, this thesis will discuss the role of 3D printing in water splitting including the fundamentals of 3D printing electrodes, design of substrates, coating of conductive layers, characterization of active materials and electrochemical performance. To enable understanding of the fundamental mechanisms and development of facile metal plating processes and to optimize system performance, the following text will outline vital background and classic work in preparation of electrodes. Additionally, this thesis summarizes the basic concepts for electrolysis and widely accepted theory for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Particularly, as prospective catalysts for OER and HER, the various pathways and classic studies of NiFe- and Ni-based catalysts are discussed. According to this basic information, the primary objective of the thesis was to fabricate 3D-printed NiFe and Ni electrodes for water splitting. The thesis therefore focuses on three general aspects, i.e., the preparation of unsupported catalysts, the development of 3D metal foam electrodes and the design and fabrication of 3D printed electrodes. The methods used range from thermal precursor conversion (polyoxomolybdates, transition-metal salts and metal hydroxides), electrodeposition of transition bimetallic species (Co-Fe sulfate-phosphate oxide-hydroxide and Ni-Fe hydroxide) to wet chemical deposition (electroless plating, chemical etching and oxidation). Temperature, reactants, and reaction time were all optimized based on electrochemical performance analyses. To this end, linear sweep voltammetry (LSV), cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), electrochemical active surface area (ESCA), electrochemical impedance spectroscopy (EIS), and other methods are used to assess the activity of catalysts and electrodes. Spectroscopic technologies (Fourier transform infrared spectroscopy (FT-IR)), electron microscopy (scanning electron microscopy (SEM) and transmission electron microscopy (TEM)), and X-ray methods (X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS)) were used to investigate the composites and the underlying catalytic mechanism. As a result, the catalysts reported have low overpotential, low Tafel slope, and high long-term stability. These projects open up new possibilities for preparation and scale-up of high-activity transition metal-based electrodes or catalysts.