Selective phosphidation of NiGa-Layered double hydroxide for hybrid supercapacitors

Abstract

• NiGa-LDHis firstly synthesized by simple hydrothermal method. • Ni 2 P and NiGa 2 O 4 are grown in situ on the NiGa-LDH by selectivephosphating. • DFT calculations confirm positive effect of phosphating on the conductivity of NiGa-LDH. • The Ni 2 P/NiGa 2 O 4 -1.2/NiGa-LDH/NF//Co 3 O 4 -C(72Wh kg-1) can light multiple LEDs in parallel. Layered double hydroxides (LDHs) materials are ideal electrode materials for supercapacitors (SCs) due to their high capacitance, large surface area and fast redox reaction. However, the limited reaction site of LDHs is one of the main obstacles to increasing the capacitance of SCs. Here, NiGa-LDH grown on nickel foam (NF) by one-step hydrothermal method is derived into Ni 2 P/NiGa 2 O 4 /NiGa-LDH/NF by partial phosphating method induced by NaH 2 PO 2 . Ni 0.5 Ga 0.5 -LDH/NF has good electrochemical performance, and the capacitance can reach 295 mAh g −1 (2124F g −1 ) when the current density is 1 A g −1 . Significantly, Ni 2 P/NiGa 2 O 4 /NiGa-LDH/NF well preserves the layered structure of LDHs, inherits the low transfer impedance of interlayer ions, and can greatly reduce the thickness of the nanosheets, exposing more active sites and speeding up the electron transfer speed. According to the first principle calculation, Ni 2 P and NiGa 2 O 4 formed by phosphating helps to increase the free electron ratio in Ni 2 P/NiGa 2 O 4 /NiGa-LDH/NF, thus improving the charge transfer behavior in electrochemical reactions. The material can provide an ultra-high electrochemical capacity of 454.7 mAh g −1 (3274F g −1 ) at 1 A g −1 . In addition, a hybrid supercapacitors (HSCs) is prepared by coupling the Co 3 O 4 -C as negative electrode with the high capacitance Ni 2 P/NiGa 2 O 4 /NiGa-LDH/NF as positive electrode. Ni 2 P/NiGa 2 O 4 /NiGa-LDH/NF // Co 3 O 4 -C HSCs provides the energy density of 72 Wh kg −1 at the power density of 800 W kg −1 with excellent long-term stability up to 8000 cycles, and is expected to be used in next-generation energy storage systems.