Modulation of Inverse Spinel Fe₃O₄ by Phosphorus Doping as an Industrially Promising Electrocatalyst for Hydrogen Evolution

Abstract

Fe‐based oxides have been seldom reported as electrocatalysts for the hydrogen evolution reaction (HER), limited by their weak intrinsic activity and conductivity. Herein, phosphorus doping modulation is used to construct inverse spinel P‐Fe3O4 with dual active sites supported on iron foam (P‐Fe3O4/IF) for alkaline HER with an extremely low overpotential of 138 mV at 100 mA cm−2. The obtained inverse spinel Fe–O–P derived from controllable phosphorization can provide an octahedral Fe site and O atom, which bring about the unusual dissociation mechanisms of two water molecules to greatly accelerate the proton supply in alkaline media. Meanwhile, the ΔGH of the P atom in Fe–O–P as an active site is theoretically calculated to be 0.01 eV. Notably, the NiFe LDH/IF(+)||P‐Fe3O4/IF(−) couple achieves an onset potential of 1.47 V (vs RHE) for overall water splitting, with excellent stability for more than 1000 h at a current density of 1000 mA cm−2, and even for 25 000 s at 10 000 mA cm−2 in 6.0 m KOH at 60 °C. The excellent catalyst stability and low‐cost merits of P‐Fe3O4/IF may hold promise for industrial hydrogen production. This work may reveal a new design strategy of earth‐abundant materials for large‐scale water splitting.

Engineering active sites on hierarchical transition bimetal oxides/sulfides heterostructure array enabling robust overall water splitting

“…In comparison of NiMoS (370, 437, and 526 mV), MoO x /MoS 2 (266, 332, and 438 mV), NiO x /Ni 3 S 2 (214, 267, and 366 mV), as-synthesized NiMoO x /NiMoS array presents the low overpotentials of 186, 225, and 278 mV at current densities of 10, 100, and 500 mA cm −2 , and delivers a large current density of 1000 mA cm −2 at 334 mV towards OER (Fig. 6b ), satisfying the requirements for commercial electrocatalytic application (for example, j ≥ 500 mA cm −2 at η ≤ 300 mV) 48 – 51 . Compared to most reported OER catalysts (Supplementary Table 5 ), the overpotential of NiMoO x /NiMoS array at 10 mA cm −2 is still lower than those of O-CoMoS (272 mV) 42 , CoS-Co(OH) 2 @MoS 2+ x (380 mV) 26 , MoS 2 /Fe 5 Ni 4 S 8 (204 mV) 27 , MoS 2 /Ni 3 S 2 (218 mV) 28 , and iron-substrate-derived electrocatalyst (269 mV) 48 , etc.…”

“…7b and Supplementary Tabel 7). Compared to the reported electrocatalysts with the large current densities (e.g., 500 and 1000 mA cm −2 ), such as NiMoN@NiFeN 65 , nickel-cobalt complexes hybridized MoS 2 66 , Ni-P-B/paper 49 , NiVIr-LDH ||NiVRu-LDH 50 , phosphorus-doped Fe 3 O 4 51 , graphdiyne-sandwiched layered double-hydroxide nanosheets 67 , N,S-coordinated Ir nanoclusters embedded on N,S-doped graphene 68 , Co 3 Mo/Cu 69 , and FeP/Ni 2 P hybrid 70 , all aforementioned analysis confirm that as-prepared NiMoO x /NiMoS array could be served as promising industrial candidate for overall water splitting. With regard to the operating stability as important metric, this typical two-electrode cell can maintain the excellent electrocatalytic activity at a large current density of 500 mA cm −2 at the voltage of 1.75 V over 500 h without obvious degradation in 1 M KOH solution at 25°C (Fig.…”

Multifunctional Electrochemical Properties of Synthesized Non-Precious Iron Oxide Nanostructures

“…Zhang et al constructed the phosphorus-doped inverse spinel Fe 3 O 4 electrocatalyst on iron foam (P-Fe 3 O 4 /IF) for alkaline H 2 production. The synthesized electrocatalyst showed noteworthy performance at a very low overpotential of 1.38 V at 100 mA/cm 2 [41]. Further, phosphorus-doped Fe 3 O 4 nanoflowers were developed on a 3D graphene (P-Fe 3 O 4 @3DG) substrate using hydrothermal and low-temperature phosphating reaction.…”

Two‐Phase Colloidal Synthesis of Amorphous Iron‐Doped Manganese Phosphate Hollow Nanospheres for Efficient Water Oxidation

“…[ 15,30 ] Aiming at this problem, heteroatom doping, which can simultaneously improve the electrical conductivity and modulate electronic structure, was utilized to elevate the intrinsic catalytic activity of active sites. [ 31–33 ] It is discovered that Fe, as an effective dopant, can increase the conductivity of NiOOH sharply. In addition, the doping of iron into the nickel phosphate induces a strong synergistic effect and significantly increases the OER catalytic activity.…”

“…[15,30] Aiming at this problem, heteroatom doping, which can simultaneously improve the electrical conductivity and modulate electronic structure, was utilized to elevate the intrinsic catalytic activity of active sites. [31][32][33] It is discovered that Fe, as Exploitation of earth-abundant, efficient and stable electrocatalysts is of great significance for the oxygen evolution reaction (OER). Herein, a facile two-phase colloidal method is developed to synthesize amorphous iron-doped manganese phosphate (a-Fe-Mn:Pi) hollow nanospheres for the first time.…”