Porous Cobalt-nickel phosphides prepared from Al-doped NiCo-LDH precursors for supercapacitor and electrocatalysis applications

Abstract

The relatively low density of active sites and poor ions transport of electrode materials are the two main barriers hindering the applications of supercapacitors and electrocatalysts. Herein, ultrafine porous nickel cobalt phosphides (NiCoP-P) nanosheets are constructed by using aluminum (Al)-doped NiCo layered double hydroxides as precursors with followed removal of Al species and subsequent phosphorization. Benefiting from the Al-induced rich active sites, ultrafine porous nanosheet structure and fast ions transport, the optimized NiCoP-P electrode delivers a high specific capacity of 1059C·g−1 at 1 A·g−1 and possesses 71 % capacitance retention even at 50 A·g−1. An asymmetric supercapacitor achieves a high energy density of 51.7 Wh·kg−1 and long-term cyclic stability (99 % capacity retention after 10,000 cycles) in KOH/PVA sol electrolyte. The optimized NiCoP-P electrocatalyst also shows great enhancement in the hydrogen evolution reaction (HER) with an onset potential of −10 mV and a Tafel slope of 60 mV·dec−1 in alkaline electrolyte. Impressively, the HER performance can still be maintained at 93.1 % after 100 h stability test, while the commercial Pt/C catalyst reduces to 71.7 % in 40 h. Our results highlight that Al doping in precursors plays key roles in creating porous nanostructured electrode materials with rich active sites, while the residual metal oxides and Al species in the pores may provide abundant hydrophilic hole surface for fast ions transport, which are essential to heighten the property of various energy-related storage and catalysis.