Ni1−2xMoxSe nanowires@ammonium nickel phosphate–MoOx heterostructures as a high performance electrocatalyst for water splitting

Abstract

NiMo-based materials are a well-known type of hydrogen evolution reaction (HER) electrocatalyst and have been intensively studied. However, the utilization of the electronic coupling effect between two different NiMo-based materials containing different anions to further boost both the HER and oxygen evolution reaction (OER) performance has not been achieved to date. Herein, we report the electrodeposition of NH₄NiPO₄·6H₂O–MoO_x on Ni_1−2xMo_xSe nanowires grown on nickel foam (NF) for the construction of heterostructured core@shell Ni_1−2xMo_xSe@NH₄NiPO₄·6H₂O–MoO_x/NF as an efficient, stable hydrogen-evolving cathode and oxygen-evolving anode for overall water splitting. The strong electronic interactions between the NH₄NiPO₄·6H₂O–MoO_x shell and Ni_1−2xMo_xSe nanowire core in combination with the peculiarities of the nickel-based oxysalt, NH₄NiPO₄·6H₂O, significantly lower the adsorption energy of water splitting intermediates on the heterostructure and improve the coverage of water adsorption and thus give rise to enhanced HER, OER, and overall water splitting performance. As a result, the heterostructured catalyst can afford a geometrical current density (j) of 10 mA cm⁻² at an extremely low overpotential (η) of 31 and 205 mV (after ohmic-drop correction) for the HER and OER, respectively, and at an alkaline cell voltage of 1.49 V for overall water splitting. Concomitantly, outstanding long-term durability is achieved for all these reactions in alkaline media.