Cationic Vacancy Defects in Iron Phosphide: A Promising Route toward Efficient and Stable Hydrogen Evolution by Electrochemical Water Splitting

Abstract

Engineering the electronic properties of transition metal phosphides has shown great effectiveness in improving their intrinsic catalytic activity for the hydrogen evolution reaction (HER) in water splitting applications. Herein, we report for the first time, the creation of Fe vacancies as an approach to modulate the electronic structure of iron phosphide (FeP). The Fe vacancies were produced by chemical leaching of Mg that was introduced into FeP as “sacrificial dopant”. The obtained Fevacancy‐rich FeP nanoparticulate films, which were deposited on Ti foil, show excellent HER activity compared to pristine FeP and Mg‐doped FeP, achieving a current density of 10 mA cm−2 at overpotentials of 108 mV in 1 m KOH and 65 mV in 0.5 m H2SO4, with a near‐100 % Faradaic efficiency. Our theoretical and experimental analyses reveal that the improved HER activity originates from the presence of Fe vacancies, which lead to a synergistic modulation of the structural and electronic properties that result in a near‐optimal hydrogen adsorption free energy and enhanced proton trapping. The success in catalytic improvement through the introduction of cationic vacancy defects has not only demonstrated the potential of Fe‐vacancy‐rich FeP as highly efficient, earth abundant HER catalyst, but also opens up an exciting pathway for activating other promising catalysts for electrochemical water splitting.

Defect Engineering Strategies for Nitrogen Reduction Reactions under Ambient Conditions

“…In summary, the anion vacancies (oxygen, nitrogen, and sulfur) can efficiently regulate the electronic structure and the band gap of the nanomaterials, which would in turn increase the number of active sites for NRR processes and enhance the catalytic performance. Apart from anion vacancies, making the cation vacancy is also an effective strategy to tailor the electronic structure variation of the various nanomaterials result in attractive properties . To date, there are very limited experimental results to systematically study the effect of cation vacancy on the NRR process at ambient conditions.…”

Phosphorus Vacancies that Boost Electrocatalytic Hydrogen Evolution by Two Orders of Magnitude

“…Cation and anion vacancies, have been investigated in electrocatalytic HER, because their ability to modify electronic structures of catalytic sites would optimize the hydrogen adsorption free energy (Δ G H ). For example, boron vacancies (Bv) have been reported to change the lattice parameters of HfB 2 ‐ZrB 2 and possibly introduce more electrons at the Fermi level to facilitate HER .…”

Cobalt Phosphides Nanocrystals Encapsulated by P‐Doped Carbon and Married with P‐Doped Graphene for Overall Water Splitting

“…Nonetheless, their bifunctional catalytic properties are needed to be further improved for reducing the overall energy output and meeting the requirements of large‐scale commercial applications. To this end, several steps have been taken, such as doping, tailoring morphology, engineering defects, and encapsulation or hybridization . Current researches reveal that combining two or three of those strategies can more efficiently modulate the electrocatalytic properties of desired TMPs nanostructures.…”