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.