Enhanced Hydrogen Evolution Reaction Performance of NiCoP by Filling Oxygen Vacancies by Phosphorus in Thin-Coating CeO.

A series of NiCoP-based electrocatalysts, which were wrapped by CeO whose oxygen vacancies (V) are partially filled with phosphorus atoms (named as NiCoP/PFVo-CeO, where refers to the consumption of NaHPO·HO), have been fabricated to improve the electrocatalytic reactivity of NiCoP toward hydrogen evolution in alkaline solution. In the novel catalysts, the P atoms fill the oxygen vacancies, elevate the chemical valence state of Ni and Co, and increase the hydride acceptors, which reinforcing the promoting effect of CeO in the hydrogen evolution reaction (HER). Moreover, the negatively charged P atoms capture the positively charged protons more easily, benefiting the Volmer step during HER. Furthermore, the synergistic effect between oxygen vacancies and the filled P atoms accelerates the migration rate of electrons/ions and increases the electrochemical active area. All of the above are advantageous to the hydrogen evolution of NiCoP/PFVo-CeO in alkaline electrolyte. As a result, the overpotential as low as 33.6 mV is achieved for NiCoP/PFVo-CeO in alkaline media to drive a current density of 10 mA cm. The reactivity is superior to that of Pt/C at a large current density along with a Tafel slope of 61.24 mV dec and long-term durability, which giving a new technology for efficient transition-metal catalyst candidates toward HER in alkaline solution.