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

Porous ultrathin 2D catalysts are attracting great attention in the field of electro/photocatalytic hydrogen evolution reaction (HER) and overall water splitting. Herein, a universal pH‐controlled wet‐chemical strategy is reported followed by thermal and phosphorization treatment to prepare large‐size, porous and ultrathin bimetallic phosphide (NiCoP) nanosheets, in which graphene oxide is adopted as a template to determine the size of products. The thickness of the resultant NiCoP nanosheets ranges from 3.5 to 12.8 nm via delicately adjusting pH from 7.8 to 8.5. The thickness‐dependent electrocatalytic performance is evidenced experimentally and explained by computational studies. The prepared large‐size ultrathin NiCoP nanosheets show excellent bifunctional electrocatalytic activity for overall water splitting, with low overpotentials of 34.3 mV for HER and 245.0 mV for oxygen evolution reaction, respectively, at 10 mA cm−2. Furthermore, the NiCoP nanosheets exhibit superior photocatalytic HER performance, achieving a high HER rate of 238.2 mmol h−1 g−1 in combination with commonly used photocatalyst CdS, which is far superior to that of Pt/CdS (81.7 mmol h−1 g−1). All these results demonstrate large‐size porous ultrathin NiCoP nanosheets as an efficient and multifunctional electro/photocatalyst for water splitting. A facile pH‐controlled wet‐chemical strategy is developed followed by thermal and phosphorization treatment to prepare large‐size porous and ultrathin NiCoP nanosheets. Such NiCoP nanosheets are controlled to ≈3.5 nm in thickness via delicately adjusting pH to balance the nucleation and growth of metal ions, which exhibit excellent electro/photocatalytic performance for water splitting, outperforming noble‐metal catalysts in electro/photocatalytic OER and HER.