Stable and Highly Efficient Hydrogen Evolution from Seawater Enabled by an Unsaturated Nickel Surface Nitride

• Published in: Advanced materials (Weinheim) Vol. 33; no. 13; pp. e2007508 - n/a
• Main Authors: Jin, Huanyu, Wang, Xuesi, Tang, Cheng, Vasileff, Anthony, Li, Laiquan, Slattery, Ashley, Qiao, Shi‐Zhang
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.04.2021
• Subjects: Anodizing; Catalysts; Clean energy; Current density; electrocatalysis; Electrolytes; Energy conversion; Heterostructures; Hydrazines; hydrogen evolution; Hydrogen evolution reactions; Hydrogen production; Hydronium ions; in situ Raman spectroscopy hydrazine oxidation; Materials science; Metal nitrides; Nickel; nickel surface nitride; Oxidation; Platinum; Seawater; Transition metals; nickel surface nitride; hydrogen evolution; in situ Raman spectroscopy hydrazine oxidation; seawater; electrocatalysis
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202007508

Electrocatalytic production of hydrogen from seawater provides a route to low‐cost and clean energy conversion. However, the hydrogen evolution reaction (HER) using seawater is greatly hindered by the lack of active and stable catalysts. Herein, an unsaturated nickel surface nitride (Ni‐SN@C) catalyst that is active and stable for the HER in alkaline seawater is prepared. It achieves a low overpotential of 23 mV at a current density of 10 mA cm−2 in alkaline seawater electrolyte, which is superior to Pt/C. Compared to conventional transition metal nitrides or metal/metal nitride heterostructures, the Ni‐SN@C has no detectable bulk nickel nitride phase. Instead, unsaturated NiN bonding on the surface is present. In situ Raman measurements show that the Ni‐SN@C performs like Pt with the ability to generate hydronium ions in a high‐pH electrolyte. The catalyst operation is then demonstrated in a two‐electrode electrolyzer system, coupling with hydrazine oxidation at the anode. Using this system, a cell voltage of only 0.7 V is required to achieve a current density of 1 A cm−2. An unsaturated nickel surface nitride exhibits efficient and stable performance for hydrogen evolution from seawater. The origin of the activity and stability of the unique surface nitride is investigated using in situ Raman spectroscopy. By coupling with hydrazine oxidation at the anode, a flow‐electrolyzer is assembled that can deliver a current density of 1 A cm−2 with a small cell voltage of 0.7 V.