Morphological and Electronic Tuning of Ni₂P through Iron Doping toward Highly Efficient Water Splitting

Abstract

Efficient water electrolysis for hydrogen production constitutes a key segment for the upcoming hydrogen economy, but has been impeded by the lack of high-performance and low-cost electrocatalysts for, ideally, simultaneously expediting the kinetics of both hydrogen and oxygen evolution reactions (HER and OER). In this study, the favored binding energetics of OER and HER reaction intermediates on iron-doped nickel phosphides are first predicted by density functional theory (DFT) simulations, and then experimentally verified through the fabrication of Fe-doped Ni2P nanoparticles embedded in carbon nanotubes using metal–organic framework (MOF) arrays on nickel foam as the structural template. Systematic investigations on the effect of phosphorization and Fe doping reveal that while the former endows a larger benefit on OER than on HER, the latter enables not only modulating the electronic structure, but also tuning the micromorphology of the catalyst, synergistically leading to both enhanced HER and OER. As a result, extraordinary performances of constant water electrolysis are demonstrated requiring only a cell voltage of 1.66 V to afford a current density of 500 mA cm–2, far outperforming the benchmark electrode couple composed of Pt/C and RuO2. Postelectrolysis characterizations combined with DFT inspection further reveal that while the Fe-doped Ni2P species are mostly retained after prolonged HER, they are in situ converted to Fe/P-doped γ-NiOOH during OER, serving as the actual OER active sites with high activity.

Rational Design of a N,S Co‐Doped Supermicroporous CoFe–Organic Framework Platform for Water Oxidation

“…Besides, generally, doping heteroatoms into electrocatalysts could effectively tune their electronic structure and improve their conductivity. In this context, various metal‐ or non‐metal‐doped MOF‐derived materials have been developed and exhibit the significantly enhanced electrocatalytic performance in contrast with their pristine materials. However, there is rarely a report about doping heteroatoms into direct MOF materials for electrocatalytic water splitting.…”

Constructing a Rod‐like CoFeP@Ru Heterostructure with Additive Active Sites for Water Splitting

“…As reported, the resulting high valence Co and Fe act as the active sites, facilitating the formation of peroxide intermediates during OER (Table S2). [20,31,32] Inspired by the remarkable HER and OER catalytic performances by choosing CoFeP@Ru, we further assembled an electrolyzer in two-electrode system with CoFeP@Ru in both the cathode and anode to test the overall water splitting. [32] As show in Figure 4e, among CoP, CoP@Ru, CoFeP@Ru electrodes, the electrolyzer with CoFeP@Ru electrodes affords the highest activity with the need for a cell voltage of � 1.76 V to drive the current density of 10 mA cm À 2 .…”

Zinc Substitution‐Induced Subtle Lattice Distortion Mediates the Active Center of Cobalt Diselenide Electrocatalysts for Enhanced Oxygen Evolution

“…[16][17][18] Moreover, previous experimental and theoretical work has reported that the incorporation of foreign metal atoms could optimize the absorption kinetic energy barrier of OER intermediates, accelerating the sluggish OER. [19][20][21] Consequently, the incorporation of metal atoms should be an efficient strategy for the modification of OER activity in TMDs.…”

“…The introduction of metal atoms with similar atomic radius and electron configuration could induce subtle distortion of the atomic arrangement via the inevitable generation of a locally unbalanced Coulomb force, which could engineer the creation of additional exposed active sites 16–18. Moreover, previous experimental and theoretical work has reported that the incorporation of foreign metal atoms could optimize the absorption kinetic energy barrier of OER intermediates, accelerating the sluggish OER 19–21. Consequently, the incorporation of metal atoms should be an efficient strategy for the modification of OER activity in TMDs.…”