Composition and electrode for phosphate sensing. In one embodiment, the composition includes a first component, a second component, and a third component. The first component is selected from a group consisting of cobalt oxide nanoparticles, tin (IV) chloride, diphenyl tin dichloride, and ammonium molybdate. The second component includes graphene oxide or reduced graphene oxide. The third component includes pyrrole or polypyrrole.