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Electrochemical water splitting is a critical reaction for the conversion of renewable energy sources. It is limited by the oxygen evolution reaction (OER) which requires high potentials to drive the reaction. The main drawback to OER catalysts is the trade-off between high activity at low potentials and stability over multiple uses. Ru metal has the lowest onset potential (∼1.3 V) and highest activity (100 - 4000 mA mg-1) due to the low energy barrier to Ru>4+ production that catalyses OER. Ru catalysts are limited by the immediate dissolution of the active species, resulting in catalysts that deteriorate in the first OER cycle. An OER electrode that delivers high activity at low potentials and remains active over multiple catalytic cycles remains a challenge. Synthesising a nanocatalyst with structural features that address both activity and stability separately offers a way to overcome this issue. This thesis focuses on creating nanoparticles with high electrochemically active surface areas made of low energy Ru surfaces. These can achieve both stability and activity by reducing the dissolution of Ru species from the highly accessible surfaces. Chapter 3 investigates the synthesis for Au-Ru branched nanoparticles with 3D branching and low index facets. By determining the key synthetic parameters to the formation of these structural features, a synthetic protocol is proposed. The growth of the Au-Ru branched nanoparticles is studied in chapter 4 using state-of-the-art transmission electron microscopy (TEM). The morphology and crystallography of intermediate nanoparticles are fully characterised to determine how these important structural features are formed. In chapter 5 the OER activity and stability of the Au-Ru branched nanoparticles are tested. Comparison to non-branched, non-faceted nanoparticles and TEM analysis of the nanoparticles after catalysis reveals the relationship between OER performance and structure. Chapter 6 investigates the synthesis of Pd-Ru bimetallic nanoparticles with core-shell and alloy structures as another means of achieving high electrochemically active surface areas and stable surfaces. By controlling synthetic variables a synthesis for nanoparticles with tunable size, shell thickness and composition is proposed for future optimisation as OER catalysts. Finally, conclusions are made across the synthesis, growth and OER performance of Ru-based bimetallic nanoparticles and opportunities for future work are proposed.