Efficient Water Oxidation at the Metal-Free, Phosphorus Acid-Functionalized Graphene Electrocatalytic Interface

The electrochemical oxygen evolution reaction (OER) is currently one of the key challenges constraining the efficient conversion of electricity into chemical fuels on a large scale. This is because the OER must overcome a high electrochemical overpotential (thermodynamic potential) due to its complexity and the four protons and four electrons it involves. While noble-metal-based electrocatalysts can lower this potential, they are among the rarest metals in the Earth's crust, expensive, and not suitable for sustainable use. Herein, we develop a facile, cost-effective synthetic approach to an inexpensive, metal-free OER electrocatalyst by preparing defective graphene nanosheets and then selectively functionalizing them with phosphorous acid species. The electrocatalytic activity of the resulting metal-free, phosphorus-doped (P-doped) graphene toward OER surpasses those of previously reported metal-free graphene-based electrocatalysts. Notably, the synthesized catalyst requires a lower overpotential to catalyze the reaction, which can be attributed to its increased surface area and reactive defect/active sites associated with the phosphorus dopants present on it. The material also shows excellent stability, maintaining its performance as well as its morphology and structures for hours in an alkaline electrolyte. The present work opens opportunities for the design and synthesis of heteroatom-doped graphene (nanocatalyst) for challenging environmentally benign, energy-related chemical transformations.