V-doped CoP Anchored on the N-P-Doped Three-Dimensional Covalently Cross-Linked Graphene As a Hydrogen Evolution Reaction Catalyst for Alkaline Water/Seawater Splitting.

Designing and synthesizing highly efficient and stable electrocatalysts of seawater electrolysis for the hydrogen evolution reaction is important for realizing green hydrogen production. Herein, a heterostructured V-doped CoP anchored on N-P-doped three-dimensional covalently cross-linked graphene (V-CoP@NPPC/3DG) electrocatalysts was synthesized with the help of V-doped ZIF-67 as an intermediate and a controlled phosphidation process. The as-prepared V-CoP@NPPC/3DG-1:5 had low overpotentials of 98.3 and 88.3 mV (at 10 mA cm) in alkaline water and artificial seawater, respectively, and the corresponding Tafel slopes were 56.4 and 51.0 mV dec. The electrolyzer with a flowing alkaline artificial seawater assembled from V-CoP@NPPC/3DG-1:5 with a commercial RuO catalyst exhibited a cell voltage of 1.54 V at 10 mA cm, which is close to that of Pt/C||RuO (1.52 V). Notably, the cell voltage of V-CoP@NPPC/3DG-1:5||RuO was lower than that of Pt/C||RuO at a high current density (>58 mA cm), which exhibited superior stability. V doping effectively enhanced the intrinsic activity of CoP, and the complexation with NPPC/3DG achieved full exposure of the active sites while enhancing the charge transfer rate during HER. This work will attract attention to the role of metal compound-carbon support interactions in enhancing the intrinsic activity, conductivity, and stability of electrocatalysts.