Highly Efficient and Stable Saline Water Electrolysis Enabled by Self‐Supported Nickel‐Iron Phosphosulfide Nanotubes With Heterointerfaces and Under‐Coordinated Metal Active Sites

Abstract

Direct seawater electrolysis is proposed as a potential low-cost approach to green hydrogen production, taking advantage of the vastly available seawater and large-scale offshore renewable energy being deployed. However, developing efficient, earth-abundant electrocatalysts that can survive under harsh corrosive conditions for a long time is still a significant technical challenge. Herein, the fabrication of a self-supported nickel-iron phosphosulfide (NiFeSP) nanotube array electrode through a two-step sulfurization/phosphorization approach is reported. The as-obtained NiFeSP nanotubes comprise abundant NiFeS/NiFeP heterointerfaces and under-coordinated metal sites, exhibiting outstanding activity and durability for the hydrogen and oxygen evolution reactions (HER and OER) in simulated alkaline-seawater solution (KOH + NaCl), with an overpotential of 380 (HER) and 260 mV (OER) at 500 mA cm -2 and outstanding durability of 1000 h. Theoretical calculations support the observed outstanding performance, showing that the heterointerface and under-coordinated metal sites synergistically lower the energy barrier of the rate-determining step reactions. The NiFeSP electrode also shows good catalytic performance for the urea oxidation reaction (UOR). By coupling UOR with HER, the bifunctional NiFeSP electrode pair can efficiently catalyze the overall urea-mediated alkaline-saline water electrolysis at 500 mA cm -2 under 1.938 V for 1000 h without notable performance degradation.

Upgrading Organic Compounds through the Coupling of Electrooxidation with Hydrogen Evolution

“…However, the splitting of seawater is seriously limited by the chloride evolution reaction (ClER) occurring at the anode, which competes with the OER and generates unfavorable chlorine and/or hypochlorite that will corrode the catalysts, membranes, and other components over time. The EOO occurs at a lower potential than the OER and ClER [110] . Thus, coupling the EOO with HER could enable seawater electrolysis to proceed at a high current density without the interfering ClER, thereby making it more promising for the large‐scale green production of hydrogen. In terms of scale‐up, feasibility investigations, including laboratory prototypes and pilot plants for industrial applicability, are essential for commercialization.…”

“…The EOO occurs at a lower potential than the OER and ClER. [110] Thus, coupling the EOO with HER could enable seawater electrolysis to proceed at a high current density without the interfering ClER, thereby making it more promising for the large‐scale green production of hydrogen. In terms of scale‐up, feasibility investigations, including laboratory prototypes and pilot plants for industrial applicability, are essential for commercialization.…”

“…The EOO occurs at a lower potential than the OER and ClER. [110] Thus, coupling the EOO with HER could enable seawater electrolysis to proceed at a high current density without the interfering ClER, thereby making it more promising for the large‐scale green production of hydrogen.…”

Aufwertung organischer Verbindungen durch Kopplung von Elektrooxidation und Wasserstoffentwicklung

“…Die Spaltung des Meerwassers wurde jedoch durch die an der Anode stattfindende Chloridentwicklungsreaktion (“chloride evolution reaction”, ClER) stark eingeschränkt, die mit der OER konkurriert und ungünstiges Chlor und/oder Hypochlorit erzeugt, sodass Katalysatoren, Membranen und andere Komponenten im Laufe der Zeit korrodieren würden. Die EOO findet bei einem niedrigeren Potenzial als die OER und die ClER statt [110] . Eine Kopplung der EOO mit der HER könnte es somit ermöglichen, die Meerwasserelektrolyse bei einer hohen Stromdichte durchzuführen, ohne die ClER zu stören, was sie für die großtechnische umweltfreundliche Wasserstoffproduktion vielversprechend macht. Was die Maßstabsvergrößerung betrifft, so sind Durchführbarkeitsuntersuchungen, einschließlich potentieller Laborprototypen und Pilotanlagen für die industrielle Umsetzung und die Kommerzialisierung unerlässlich.…”

“…Die EOO findet bei einem niedrigeren Potenzial als die OER und die ClER statt. [110] Eine Kopplung der EOO mit der HER könnte es somit [106] Urheberrecht 2020, Nature Publishing Group. c) Gekoppelte Epoxidierung von Cycloocten und HER.…”