Polyoxometalate as the assembly material to self-assembled Ni(OH)₂ nanosheets with electrocatalytic performance

Developing non-noble metal-based electrocatalyst with high catalytic activity is essential for advancing hydrogen energy technologies. This study introduces a hydrothermal method for synthesizing order Ni(OH)₂ nanosheets, with H₃O₄₀PW₁₂ (denoted as PW₁₂) loaded onto reduced graphene oxide (rGO) coated on nickel foam (referred to as PW₁₂-Ni(OH)₂/rGO). This method contrasts with the electrodeposition of Ni(OH)₂, where PW₁₂ is added to the synthetic system to direct the assembly and morphology of the Ni(OH)₂ through a hydrothermal reaction. In this work, the nickel foam acts dual roles as both the substrate and the source of nickel for the formation of Ni(OH)₂. The PW₁₂-Ni(OH)₂/rGO nanosheets, when successfully prepared and loaded onto the nickel foam (NF), exhibited superior electrocatalytic activity for the hydrogen evolution reaction (HER) in an alkaline electrolyte, achieving a current density of 10 mA·cm⁻² at an overpotential of 69 mV. Furthermore, we endeavored to expand the application of this material towards the oxygen evolution reaction (OER) by preparing PW₁₂-(Fe/Co)Ni(OH)₂/rGO through the addition of metal cations. This nanocomposite displayed outstanding electrocatalytic activity in alkaline electrolytes, with a current density of 10 mA·cm⁻² at an overpotential of 211 mV, and demonstrated excellent stability over a 50 h period in a 1 M KOH solution. The results presented in this paper offer an effective strategy for the preparation of polyoxometalate-based inorganic materials with diverse functionalities, applicable to both HER and OER.