Ultrahigh‐Performance Pseudocapacitor Electrodes Based on Transition Metal Phosphide Nanosheets Array via Phosphorization: A General and Effective Approach

Abstract

In this study, a general and effective phosphorization strategy is successfully demonstrated to enhance supercapacitor performance of various transition metals oxide or hydroxide, such as Ni(OH) 2 , Co(OH) 2 , MnO 2 , and Fe 2 O 3 . For example, a 3D networked Ni 2 P nanosheets array via a facile phosphorization reaction of Ni(OH) 2 nanosheets is grown on the surface of a Ni foam. The Ni foam-supported Ni 2 P nanosheet (Ni 2 P NS/NF) electrode shows a remarkable specifi c capacitance of 2141 F g −1 at a scan rate of 50 mV s −1 and remains as high as 1109 F g −1 even at the current density of 83.3 A g −1 . The specifi c capacitance is much larger than those of Ni(OH) 2 NS/NF (747 F g −1 at 50 mV s −1 ). Furthermore, the electrode retains a high specifi c capacitance of 1437 F g −1 even after 5000 cycles at a current density of 10 A g −1 , in sharp contrast with only 403 F g −1 of Ni(OH) 2 NS/NF at the same current density. The similar enhanced performance is observed for Ni 2 P powder, which eliminates the infl uence of nickel foam. The enhanced supercapacitor performances are attributed to the 3D porous nanosheets network, enhanced conductivity, and two active components of Ni 2+ and P δ − with rich valences of Ni 2 P.

Substrate‐Friendly Growth of Large‐Sized Ni(OH)2 Nanosheets for Flexible Electrochromic Films

“…The freestanding Ni(OH) 2 powder collected from the mother liquid can further confirm the α‐Ni(OH) 2 crystalline phase (Figure S8, Supporting Information). The energy‐dispersive X‐ray spectroscopy (EDX) spectra of both Ni(OH) 2 /FTO and Ni(OH) 2 /MoO 3 /FTO glass in Figure b show O and Ni peaks at 0.52, 0.85, and 7.47 keV, corresponding to the composition of Ni(OH) 2 nanosheets . Mo peak can be seen at 2.30 keV in Ni(OH) 2 /MoO 3 /FTO glass, as the sprayed MoO 3 nanobelts layer .…”

Metal Phosphides and Phosphates‐based Electrodes for Electrochemical Supercapacitors

“…For example, NiP x arrays can be made by low‐temperature phosphorization of nickel arrays grown on carbon cloth (CF@Ni) by electrodeposition, when they are mounted in the downstream of the furnace . Through a similar procedure, interconnected 3D networks of Ni 2 P nanosheets are formed from Ni(OH) 2 nanosheets grown on nickel foam . Hierarchical 3D NiCoOP@C hybrids were successfully prepared by phosphorization treatment of Ni x Co 1−x O@C grown on nickel foam .…”

“…Hierarchical 3D NiCoOP@C hybrids were successfully prepared by phosphorization treatment of Ni x Co 1−x O@C grown on nickel foam . In these hybrid‐type structures, carbon cloth and nickel foam are acting as the conducting substrates …”

“…Therefore, the NiP bonds bear a lower Δχ, and therefore nickel phosphides show much better conductivity than the oxide counterpart. In Ni–based electrode materials, the charge storage in alkali environment is ascribed to the Ni 2+ /Ni 3+ pair, which can be described by Equations and below …”

“…Phosphorus is a multivalent nonmetal of the nitrogen group, which is also one of the most useful and well‐established donor atoms in coordination chemistry . There is a large group of phosphorus compounds, including metal phosphides and metal phosphates, some of which have been studied for better performing electrodes for energy storage and other applications, such as in lithium ion batteries, supercapacitors, and catalysts . Indeed, phosphorus can react with most of the elements in the periodic table to form a diverse class of phosphides .…”