CoMoP/NiFe-Layered Double-Hydroxide Hierarchical Nanosheet Arrays Standing on Ni Foam for Efficient Overall Water Splitting
Wanshan Mai, Qian Cui, Ziqiong Zhang, Kaikai Zhang, Guoqiang Li, Lihong Tian, Wei Hu
Abstract
For efficient water splitting and replacement of expensive Pt or Ir with the earth-abundant materials, we have designed a heterostructure based on the two-dimensional (2D) bimetallic phosphide and layered double hydroxide (LDH) to construct the electrode assembly (i.e., CoxMo1P/NiFe-LDH) and observed its catalytic activities for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting. The optimized Co5.0Mo1P/NiFe-LDH hybrid obtained via the hydrothermal–phosphating–electrodeposition process consists of hierarchical nanosheet arrays including some silky and ultrathin NiFe-LDH nanosheets and numerous tiny and cross-linking Co5.0Mo1P nanoplates. Electrochemical tests display that Ni foam (NF)/Co5.0Mo1P/NiFe-LDH not only exhibits outstanding performance toward both HER and OER with an HER overpotential (η at 10 mA/cm2) of 98.9 mV and an OER overpotential (at 50 mA/cm2) of 225 mV outperforming NF/Co5.0Mo1P and NF/CoP but also presents superb stability in 1.0 M KOH. Moreover, it affords a cell voltage for water splitting of 1.68 V at 50 mA/cm2 with an excellent durability for more than 27 h. The abundant and intensive exposure of active sites provided by 2D porous and hierarchical nanosheet arrays and a strong electronic coupling and fast electronic transmission between various interfaces would explain the improved performance. In addition, the anchor effect between Co/Mo phosphides and NiFe-LDHs prevents corrosion of electrolyte solution and slows down the dissolution of the P element. This efficient and highly stable bifunctional electrode can serve as a practical electrode for electrochemical energy storage and conversion.