Crystalline Ni₅P₄/amorphous CePO₄ core/shell heterostructure arrays for highly-efficient electrocatalytic overall...

Exploring low-cost and highly efficient bifunctional electrocatalysts for overall water splitting has become a research focus recently. Crystalline/amorphous core/shell heterostructures have great potential for applications in the field of electrocatalytic overall water splitting. However, related research is still challenging. Herein, crystalline Ni₅P₄ nanosheets/amorphous CePO₄ nanocrystals core/shell heterostructure arrays were developed for electrocatalytic overall water splitting. It is shown that the heterostructure array required competitive HER and OER overpotentials of 94 and 191 mV in alkaline environment (10 mA/cm²), respectively. Encouragingly, the symmetrical two-electrode system constructed with the heterostructure array only required an ultra-low cell voltage of 1.535 V to achieve a current density of 10 mA/cm². This indicates the system has huge potential in overall water splitting. The electrocatalytic mechanism was studied systematically by combining theoretical calculation and experimental characterization. It was found that the surface coating of amorphous CePO₄ could not only significantly increase the electrochemical active surface area and improve the charge transfer of crystalline Ni₅P₄ nanosheets, but could also regulate d-band center of Ni₅P₄ and optimize the adsorption towards reaction intermediates in water splitting. The results not only provide an excellent crystalline/amorphous core/shell heterostructure bifunctional electrocatalyst for overall water splitting but also greatly expand the application of rare earth metal phosphate CePO₄.