Energy storage technology is required to compensate for the renewable energy sources shortcomings in providing continuous supply of energy. Owing to the high gravimetric energy density of hydrogen (H2), hydrogen gas is predicted to play a significant role in the future of renewable energy distribution system. However, majority of global hydrogen energy supplies are originated from fossil fuel reforming process. Hence, it is preferred that hydrogen is produced from a zero carbon footprint process such as electrochemical water splitting. Nevertheless, the exorbitant cost of the electrode materials such as Pt, Ir and Ru have restricted the widespread application of water electrolyser. Consequently, the development of cheaper and effective electrodes, based Earth-abundant components is critical. Owing to the unique electrochemical and mechanical properties of carbon nanomaterials, they have been extensively applied in the development processes of advanced electrocatalysts. The electrochemical activity of carbon nanomaterial such as multiwalled carbon nanotube (MWCNT) and carbon black (CB) can be finely tuned via the functionalisation or doping with heteroatoms such as nitrogen and sulfur. The presence of these heteroatoms is known to disrupt the electronic neutrality of carbon atoms in the graphitic structure, inciting change in electrochemical performances. However, studies relating to the role of oxygen on the electrochemistry of carbon materials remain scarce. This thesis studies the effect of the surface-bound oxygen functionalities towards the electrocatalytic properties of MWCNT and CB. It is shown that there is an oxygen content-electrochemical performance interdependency in the analysed carbon nanomaterials, in this case are MWCNT and CB. The contribution from metal impurities that are present in MWCNT such as Ni and Fe was also considered and systematically investigated. Their electrochemical contribution towards the observed oxygen evolution reaction activity was elucidated. Inspired from the promising activity of these impurities, a highly active overall water-splitting electrocatalyst based on a rational catalyst design is proposed at the final chapter of the thesis. From this thesis, a promising alkaline water-splitting catalyst that exhibits higher activity than the Pt-group based electrocatalyst has been conceived.