Stable and Efficient Oxygen Evolution from Seawater Enabled by Graphene-Supported Sub-Nanometer Arrays of Transition Metal Phosphides

Electrolysis of seawater will alleviate strain on fresh water scarcity. Non-noble metal compounds as substitutes for precious metals for oxygen evolution reaction (OER) have been intensively studied. However, to make OER electrocatalyst efficient and stable in seawater is still an issue to be solved. In view of this, an attempt to fabricate nickel foam (NF)-enclosed reduced graphene oxide (rGO) supported sub-nanometer arrays of NiFe phosphide is reported. The as-obtained NiFeP/P-doped rGO/NF (NiFeP/P-rGO/NF) at current densities of 100 and 400 mA cm(-2) shows overpotentials of 290 and 340 mV respectively, well below 490 mV overpotential that avoided triggering chloride oxidation in seawater (1 m KOH+1 m NaCl). The Tafel slope of NiFeP/P-rGO/NF is as low as 71.9 mV dec(-1). Moreover, no considerable loss of current density is observed after 450 h at 35 mA cm(-2). This strategy is extended to fabricate CoFeP/P-rGO/NF and IrO2/rGO/NF and they also show superior activity. The combination of ultrathin NiFeP arrays and conductive network of rGO are the key to superior activity. Hydrophobicity of the rGO is accountable for good durability in seawater.