Porous Pd/NiFeOx Nanosheets Enhance the pH‐Universal Overall Water Splitting

Abstract Modulating the morphology and chemical composition is an efficient strategy to enhance the catalytic activity for water splitting, since it is still a great challenge to develop a bifunctional catalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) over a wide pH range. Herein, Pd/NiFeO x nanosheets are synthesized with tightly arranged petal nanosheets and uniform mesoporous structure on nickel foam (NF). The porous 2D structure yields a larger surface area and exposes more active sites, facilitating water splitting at all pH values. The overpotential of Pd/NiFeO x nanosheets for OER is only 180, 169, and 310 mV in 1 m KOH, 0.5 m H 2 SO 4 , and 1 m phosphate‐buffered saline (PBS) conditions at 10 mA cm −2 current density, as well as excellent HER activity with ultralow overpotential in a wide pH range. When using porous Pd/NiFeO x nanosheets as bifunctional catalysts for water splitting, it just required a cell voltage of 1.57 V to reach a current density of 20 mA cm −2 with nearly 100% faradic efficiency in alkaline conditions, which is much lower than that of benchmark Pt/CǁRuO 2 (1.76 V) couples, along with the improving stability benefiting from the good corrosion resistance of the inner NiFeO x nanosheets.