Construction of CoP/NiCoP Nanotadpoles Heterojunction Interface for Wide pH Hydrogen Evolution Electrocatalysis and Supercapacitor

Abstract

Constructing well defined nanostructures is promising but still challenging for high‐efficiency catalysts for hydrogen evolution reaction (HER) and energy storage. Herein, utilizing the differences in surface energies between (111) facets of CoP and NiCoP, a novel CoP/NiCoP heterojunction is designed and synthesized with a nanotadpoles (NTs)‐like morphology via a solid‐state phase transformation strategy. By effective interface construction, the disorder in terms of electronic structure and coordination environment at the interface in CoP/NiCoP NTs is created, which leads to dramatically elevated HER performance within a wide pH range. Theoretical calculations prove that an optimized proton chemisorption and H2O dissociation are achieved by an optimized phosphide polymorph at the interface, accelerating the HER reaction. The CoP/NiCoP NTs are also proved to be excellent candidates for use in supercapacitors (SCs) with a high specific capacitance (1106.2 F g−1 at 1 A g−1) and good cycling stability (nearly 100% initial capacity retention after 1000 cycles). An asymmetric supercapacitor shows a high energy density (145 F g−1 at 1 A g−1) and good cycling stability (capacitance retention is 95% after 3200 cycles). This work provides new insights into the catalyst design for electrocatalytic and energy storage applications.

Large‐Size, Porous, Ultrathin NiCoP Nanosheets for Efficient Electro/Photocatalytic Water Splitting

“…[ 51–53 ] For P 2p 1/2 spectrum (Figure 3f), the peak at the binding energy of 129.9 eV corresponds to P 2p 1/2 , which is the characteristics of phosphorus species. [ 19,29 ] Meanwhile, a predominate peak of oxidized phosphorus species located at the binding energy of 133.5 eV is also observed. [ 29,54 ] Notably, the binding energies of nickel species and cobalt species in the NiCoP nanosheets positively shift as respect to that of metallic nickel (852.6 eV) and cobalt (778.2 eV), respectively, whereas the peak of phosphorus species shifts to lower binding energy compared with phosphorus element (130.2 eV).…”

“…The negatively charged P atoms with strong electrostatic affinity can effectively capture protons, thereby promoting hydrogen production. [ 3,18,19 ] The catalytic activity of Ni x Co y P z is closely related to its surface properties and electronic structures, and can be improved by increasing the quantity of exposed active sites and optimizing its electronic structures by rationally tuning the morphology, surface area, defects and composition of Ni x Co y P z . [ 20–26 ] For example, Liu and co‐workers adopted controllable oxygen doping strategy to obtain an efficient NiCoP electrocatalyst with a hydrogen adsorption energy close to zero and abundant exposed active sites.…”

“…Generally, NiCoP is derived from NiCo oxide (NiCoO x ) via phosphorus substitution using chemical vapor deposition method, in which the morphology of NiCoP inherits from NiCoO x . [ 18,19,29,45–47 ] Recently, Guo et al reported a general wet‐chemical approach to synthesize large‐size, ultrathin 2D metal oxide nanosheets based on graphene oxide (GO) template, in which the nucleation and growth of metal ions are balanced during hydrolysis to prevent forming precipitates. [ 48 ] Based on this approach, only single‐metal oxide nanosheets with micron‐scale size and several nanometer‐thickness have been obtained.…”

Electrocatalyst engineering and structure-activity relationship in hydrogen evolution reaction: From nanostructures to single atoms

“…(1) Most of the reported heterostructures show welldefined nanostructures, substantially exposing active sites, which can offer more adsorption sites for hydrogen intermediates. Lin et al [123] recently reported CoP/ NiCoP nanotadpoles (NTs)-like heterojunction ( Fig. 7k and l) for efficient electrocatalytic HER over a wide pH range ( Fig.…”

“…The electronic redistribution can be well reflected by the XPS, especially the synchrotron-radiation-based X-ray absorption spectroscopy (XAS). Recent studies suggested that the formation of the heterointerfaces in heterostructured Ni/NiCoP NHs and CoP/ NiCoP NTs can tune the electronic structures of the catalysts, thus promoting the HER process [123,124].…”