Bifunctional Electrocatalyst (HER/UOR) Derived from Keplerate-Type Polyoxometalate for Energy-Saving Hydrogen Production

Abstract

The development of energy-saving hydrogen production technology coupled with the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) is critical for addressing the energy crisis and environmental contamination. Herein, we report a bimetallic electrocatalyst of Ni/Mo2C nanoparticles coated on N-doped carbon layers (Ni/Mo2C@NC), derived from a facile one-step pyrolysis of the precursor containing a Keplerate-type polyoxometalate (Mo153) and nickel acetate with dicyandiamide (DCA) as the carbon/nitrogen source. Ni/Mo2C@NC shows outstanding bifunctional electrocatalytic activity, requiring overpotentials of 161 and 192 mV to drive 10 mA cm–2 for HER in basic and acidic electrolytes, respectively, with the corresponding Tafel slopes of 86 and 84 mV dec–1. For UOR, a relatively low potential of 1.407 V is required to achieve 10 mA cm–2 with a Tafel slope of 46 mV dec–1. When employed in a two-electrode urea electrolysis cell, merely 1.458 V can drive 10 mA cm–2, substantially lower than that required for water splitting, including HER and OER. Moreover, Ni/Mo2C@NC demonstrates good, long-term durability exceeding 24 h for both HER and UOR. This work can provide design-assistant insights using POMs for energy-saving hydrogen production.