Herein, Co(II) citrate complex nanoparticles (CoC NPs) were synthesized by a simple protocol and were subsequently immobilized on GO sheets to provide a binary nanocomposite termed as CoC/GO. By conducting direct pyrolysis of citric acid (CA) in the presence of CoC NPs, the self-condensation reaction of CA facilitated in situ construction of the GO support and concurrent grafting of complex NPs onto its as-developing surface. The last step was to investigate the feasibility of using the resulting CoC/GO nanocomposites for visible light-induced water splitting, with the end goal of producing hydrogen gas. At room temperature and without the addition of any exogenous chemicals, the catalytic activity of CoC/GO was boosted to a maximum turnover frequency of 173.99 h−1. This study presents an innovative, simple, cost-efficient, and eco-friendly method for surface modification of GO sheets, which may open up new avenues for the development of versatile GO-based nanomaterials capable of performing optimally in every given scenario.