Three‐dimensional Porous Co Doped VN Nanosheet Arrays as Cathode Electrode for Alkaline Water Electrolysis

Abstract

Alkaline anion exchange membrane (AEM) water electrolysis is currently the most promising hydrogen production technology, and the development of non-precious metal-based hydrogen evolution reaction (HER) electrocatalysts with high performance and low price is one of the greatest challenges for large-scale AEM. Although the reaction mechanism of HER under alkaline conditions is very different from acidic conditions, many researchers still believe that the HER activity is determined by Gibbs free energy for hydrogen absorption (ΔG H* ) in all pH environments. In the meantime, vanadium-based nitrides are rarely reported as alkaline HER catalysts due to the large density unoccupied orbitals of V cause high ΔG H* value. Herein, we prepare nanoporous VN sheet arrays (NSAs) with high specific surface by hydrothermal-nitriding treatment, and then optimize its electronic structure via varying the doping amount of Co. As a result, the Co doped VN NSAs display an outstanding HER performance (overpotential of 37 mV at 10 mA cm À 2 and Tafel slope of 41 mV dec À 1 ), which is even close to the commercial Pt/ C catalyst under alkaline conditions. Moreover, by combining theoretical calculations and HER performances under acid and basic conditions, we find that the adsorption/desorption of hydrogen on activity sites could not fully revealed by ΔG H* . This work opens up a new door to understand the mechanism of alkaline HER reaction and the development of HER electrocatalysts.

Nickel‐Based Electrocatalysts for Hydrogen Oxidation Reaction Under Alkaline Electrolytes

“…The crystal structures, morphologies and physical properties of metal subjects would be maintained well with a suitable doping amount, for which the catalytic features could be well inherited. Meanwhile, the charge redistribution between doping atoms and their neighboring sites could tailor the d‐orbital band structures and oxidation states of metals [11a,b] . Besides, heteroatoms doping would lead to slightly lattice expansion with distortion or strain effect, [12] which further facilitates the optimization of electronic structures.…”

Metal nitride-based nanostructures for electrochemical and photocatalytic hydrogen production

“…By simple doping of Co to VN nanosheet array samples, the HER activity can be significantly enhanced. For example, Co-doped VN registered a small overpotential of 37 mV and a Tafel slope of 41 mV/dec which is close to those of Pt/C [ 227 ]. It was demonstrated that the high electronic conductivity, high BET surface area (26.5 m 2 /g), high electrochemical double-layer capacitance (40.3 mF cm −2 ) and optimized hydrogen adsorption Gibbs-free energy facilitates a rapid electron transport and enhance HER performance in comparison to VN nanosheet array.…”