Self-Standing CoP Nanosheets Array: A Three-Dimensional Bifunctional Catalyst Electrode for Overall Water Splitting in both Neutral and Alkaline Media

It is highly attractive, but still remains a huge challenge, to develop efficient non-noble-metal electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under neutral and alkaline conditions. In this paper, we report that CoP nanosheet arrays on carbon cloth (CoP NA/CC), derived from alpha-Co(OH)(2) NA/CC, behaves as a three-dimensional bifunctional water-splitting catalyst electrode with high activity and durability in neutral and alkaline media. Such CoP NA/CC demands overpotentials of 145 and 52 mV to afford 10 mA cm(-2) for the HER in 1.0 M phosphate buffer solution (PBS) and 1.0 M KOH, respectively, with much superior activity to alpha-Co(OH)(2) NA/CC. It can be attributed to the more thermo-neutral hydrogen adsorption free energy for CoP than alpha-Co(OH)(2), according to density functional theory calculations. This electrode also demonstrates superior OER activity over alpha-Co(OH)(2) NA/CC and needs overpotentials of only 536 and 300 mV to drive 10 mAcm(-2) at neutral and alkaline pH, respectively. The two-electrode water electrolyzer using CoP NA/CC as both the cathode and anode shows a 2 mAcm(-2) water-splitting current at a cell voltage of 1.60 V in 1.0 M PBS and needs 1.65 V for 10 mAcm(-2) under alkaline condition with excellent stability.