Two-dimensional CoP-Ni₂P heterostructure nanosheets intertwined with carbon nanotubes as catalysts for enhanced hydrogen generation and urea oxidation

Electrocatalytic water splitting is an efficient way to provide green energy hydrogen (H₂), and it is a challenge to prepare high-efficiency and inexpensive electrocatalysts. In this work, we constructed two-dimensional (2D) CoP-Ni₂P heterostructure nanosheets intertwined with carbon nanotube (CoP-Ni₂P/CNT) as bifunctional electrocatalysts with excellent performance. The CoP-Ni₂P/CNT exhibits the outstanding HER (an overpotential of 82 mV at 10 mA cm⁻² and Tafel slope of 62.6 mV dec⁻¹) and OER (an overpotential of 210 mV at 10 mA cm⁻² and Tafel slope of 97.4 mV dec⁻¹) activities. The optimal electrocatalytic performance of the CoP-Ni₂P/CNT are ascribed to the following factors: i) the introduction of CNTs into electrocatalysts is helpful to reduce excessive aggregation of nanosheets and enhance the electron transport rate; ii) the 2D nanosheet structure and interface designing of CoP-Ni₂P/CNT expose more active sites, which are beneficial to enhance electrocatalytic performance toward HER and OER. In a two-electrode system, the cell voltage is 1.39 V to reach 10 mA cm⁻² after adding 0.1 M urea into 1 M KOH electrolyte. This obviously low voltage implies the feasibility of realizing energy-saving hydrogen production and urea degradation. All these results reveal the CoP-Ni₂P/CNT is a promising bifunctional electrocatalyst toward practical application.