“One stone three birds” plasma engraving strategy to boost the hydrogen evolution reaction activity of layered double hydroxides

Abstract

Possessing large specific surface areas and rich metal redox sites, layered double hydroxides (LDHs) are potentially suitable oxygen evolution reaction catalysts. It is a pity that they usually show poor hydrogen evolution reaction (HER) activity on account of the limited conductivity and deficient active sites. Taking NiFe LDH nanosheets as an example, we develop a “one stone three birds” plasma engraving strategy to enhance the HER activity of NiFe LDH. The “three birds,” including the reduction of Ni2+ to Ni nanoparticles (Ni NPs), generation of more oxygen vacancies (Ov), and exfoliation of nanosheets into much thinner ones, can obviously improve the conductivity and active sites of NiFe LDH. The plasma processing can also enhance water adsorption and accelerate the Volmer step during HER. As expected, the plasma-engraved NiFe LDH (PEH) exhibits enhanced HER activity with a low overpotential of 22 mV at 10 mA cm−2 and a small Tafel slope of 38 mV dec−1 in 1 M KOH, much better than NiFe LDH (202 mV, 145 mV dec−1). By combining optical emission spectroscopy diagnosis and structural/electrochemical characterizations, the relationship among the electron excitation temperature (Texc) in plasma, the amount of Ni NPs and Ov in PEH, and the HER activity of PEH is established. Excitingly, the PEH also displays splendid HER activity in both alkaline real seawater and overall water splitting.

Nanoporous Nickel Cathode with an Electrostatic Chlorine-Resistant Surface for Industrial Seawater Electrolysis Hydrogen Production

“…Alkaline seawater electrolysis based on offshore renewable energy electricity has emerged as a sustainable and economically viable technology for green hydrogen production. − Electrodes are at the heart of the electrolytic system and play a pivotal role in determining the energy efficiency of such a electricity–hydrogen conversion process. − Metallic Ni mesh/foam serves as the cathode material in a commercially mature alkaline water electrolysis system. − However, the Ni mesh/foam materials suffer from significant deficiencies in a seawater electrolysis environment: (I) chloride-ion-associated Ni metal corrosion, resulting in the poor structural and electrochemical stability of Ni mesh/foam electrodes; − (II) limited electrode surface area and (III) low intrinsic activity of metallic Ni sites, both of which lead to limited electrocatalytic activity and high working overpotentials. − To date, developing a Ni-based cathode with high electrocatalytic activity and stability for industrial seawater electrolysis remains a tough challenge.…”