Transforming Ni-Coagulated Polyferriertic Sulfate Sludge into Porous Heteroatom-Doped Carbon-Supported Transition Metal Phosphide: An Efficient Catalyst for Oxygen Evolution Reaction

The transformation of sludge waste from wastewater treatment plants into functional materials is an attractive prospect. Herein, the successful synthesis of mesoporous heteroatom-doped carbon-supported NiFe phosphide (FeNi2P@HDC) from Ni-coagulated iron sludge by forming a biogenic precursor via incubation of the sludge with Shewanella oneidensis MR-1, followed by a simple pyrolysis process, is reported. The incubation results in the formation of a solid chemical bonding between bacteria and the surface of the newly formed mineral, which is beneficial for producing a desirable microstructure and chemical composition. The as-synthesized FeNi2P@HDC shows a superior oxygen evolution reaction (OER) performance, evident from the data, including a low overpotential of 280mV to reach a current density of 10mA cm(-2) and a small Tafel slope of 56mVdec(-1) under alkaline conditions, which is comparable with that of the majority of the reported Ni and/or Fe phosphide catalysts in the literature and better than the state-of-the-art RuO2 catalyst. Such a good performance seems to be the result of the synergistic effect of the intrinsic activity of FeNi2P nanoparticles and the strong interaction between FeNi2P and heteroatom-doped graphene-like carbon support.