Ultralow Fe^III Ion Doping Triggered Generation of Ni₃S₂ Ultrathin Nanosheet for Enhanced Oxygen Evolution Reaction

Abstract

Oxygen evolution reaction (OER) is a sluggish process for water electrolysis to produce hydrogen fuel. In this work, ultralow level of Fe(III) ion triggered Ni3S2 nanosheet grownon nickel foam (NF) for the enhanced electrocatalytic activity towards OER was reported for the first time. The OER electrocatalytic activity of the Fe(III)−Ni3S2/NF electrode was improved remarkably by adding only 2.1 (at.)% Fe(III) ion into the developed electrode and it merely requires an overpotential of η=213 mV to afford a current density of 10 mA cm−2, significantly lower than both the Ni3S2/NF electrode (η=324 mV) and the benchmark RuO2/NF electrode (η=240 mV). As far as we know, this is the lowest overpotential to achieve the same value based on the reported Ni‐based sulfides. Meanwhile, the kinetic studies show that the Fe2.1%−Ni3S2/NF electrode possessed a much smaller Tafel slope (33.2 mV dec−1) than that of Ni3S2/NF electrode (72.1 mV dec−1), demonstrating a fast reaction pathway. Further investigations attribute the enhanced OER activity to: (i) the addition of appropriate Fe(III) ions are favorable for the formation of interconnected Ni3S2 ultrathin nanosheets, rather than keeping the original wrinkled fusiform nanorods, thus leading to a 2‐fold significantly enlarged electrochemical active surface areas,(ii) the improved surface wettability can result in an enhanced compatibility and affinity of the catalyst with the electrode, which is good for gas bubble evolution and (iii) the enhanced intrinsic electrocatalytic activity due to the electronic structure regulating effect of Fe(III) lead to a fast shuttling of charge transfers during OER between the electrode and the solution.

Ultrathinning Nickel Sulfide with Modulated Electron Density for Efficient Water Splitting

“…Such direct in situ transformation of NF into Fe 0.9 Ni 2.1 S 2 @ NF ensures the firm contact between the active sites and conductive support, which is important for the electrocatalytic performance of catalysts. [43] The X-ray diffraction (XRD) patterns of the as-grown Fe x Ni 3-x S 2 @ NF were shown in Figure 2a. Compared with the XRD pattern of original NF, except for the three main peaks indexed to NF, four peaks centered at 21.8°, 31.1°, 50.1°, and 55.2° for all Fe x Ni 3-x S 2 can be identified, corresponding well to (101), (110), (113), and (122) facets of Ni 3 S 2 , respectively (Figure 2a,b).…”

“…Such direct in situ transformation of NF into Fe 0.9 Ni 2.1 S 2 @ NF ensures the firm contact between the active sites and conductive support, which is important for the electrocatalytic performance of catalysts. [ 43 ]…”

Tuning the intrinsic catalytic activities of oxygen-evolution catalysts by doping: a comprehensive review

“…Like in metal oxides and hydroxides, Fe doping is evident in significantly improving the OER activity of TM sulfides. 139,140 147 257 mV @ 50 mA cm -2 81 24 h @ 0.6 V vs Ag/AgCl 1 M KOH Co-doped WS2 148 303 mV @ 10 mA cm -2 79 -1 M KOH CoFeS/CNT-P 1000 149 309 mV @ 100 mA cm -2 47 12 h @ 20 mA cm -2 1 M KOH Fe-doped CoS 141 290 mV @ 10 mA cm -2 52.6 10 h @ 10 mA cm -2 1 M KOH Fe-doped Co9S8 142 270 mV @ 10 mA cm -2 70 10 h @ 270 mV 1 M KOH Fe-doped NiS2 143 231 mV @ 100 mA cm -2 43 15 h @ 20 mA cm -2 1 M KOH Fe-doped Ni3S2 144 223 mV @ 200 mA cm -2 55.7 14 h @ 223 mV 1 M KOH Fe-doped Ni3S2/NF 139 249 mV @ 100 mA cm -2 42 20 h @ 270 mV 1 M KOH Fe2.1% doped Ni3S2/NF 140 213 mV @ 100 mA cm -2 33.2 -1 M KOH Fe-doped H-CoMoS 145 282 mV @ 10 mA cm -2 58 1 M KOH Ni1.29Co1.49Mn0.22S4 150 348 mV @ 10 mA cm -2 65 40,000 s @ 10 mA cm -2 1 M KOH N-doped Co9S8/G 151 409 mV @ 10 mA cm -2 82.7 -0.1 M KOH Ni-doped FeS 152 228 mV @ 10 mA cm -2 53 10 h @ 1.47 V vs RHE 1 M KOH N2-NiS2-500 153 270 mV @ 10 mA cm -2 40 h @ 270 mV 1 M KOH (N-Ni3S2@C)/NF 154 310 mV @ 100 mA cm -2 75 20 h @ 1.70 V vs RHE 1 M KOH N-doped NiS/NiS2 155 270 mV @ 10 mA cm -2 99 20 h @ 270 mV 1 M KOH P-doped Co-Ni-S Nanosheets 156 296 mV @ 100 mA cm -2 61.1 16 h @ 10 mA cm -2 1 M KOH P-Ni3S2/NF 157 256 mV @ 10 mA cm -2 30 30 h @ 1.525 V vs RHE 1 M KOH P-Ni3S2/NF 158 306 mV @ 100 mA cm -2 99 10 h @ 1.54 V vs RHE 1 M KOH (P-(Ni,Fe)3S2/NF 159 196 mV @ 10 mA cm -2 30 15 h @ 295 mV 1 M KOH Zn-doped Ni3S2 160 330 mV @ 100 mA cm -2 87 20 h @ 300 mV 1 M KOH Metal selenides Fe-doped CoSe2/NF 161 256 mV @ 100 mA cm -2 35.6 10 h @ 231 mV 1 M KOH Ag-doped CoSe2 nanobelts 162 320 mV @ 10 mA cm -2 56 -0.1 M KOH B-doped Fe5Co4Ni20Se36 163 279.8 mV @ 10 mA cm -2 59.5 10 h @ 10 mA cm -2 1 M KOH Co-doped NiSe 164 380 mV @ 100 mA cm -2 111 >10 h @ 320mV 1 M KOH Co-doped Nickel selenide 165 275 mV @ 30 mA cm -2 63 24 h @ 1.5 V vs RHE 1 M KOH Co0.75Fe0.25(S0.2Se0.8)2 166 293 mV @ 10 mA cm -2 77 -1 M KOH Cu-14-Co3Se4/GC…”

Efficient Oxygen Evolution and Gas Bubble Release Achieved by a Low Gas Bubble Adhesive Iron–Nickel Vanadate Electrocatalyst

“…[13][14][15][16][17] In addition, anionic modification facilitates the formation of active peroxide intermediates (OOH)by modulating the catalytic metal centers. [18][19][20][21] Unlike cationic substitution with another metal which can cause the partial loss of active sites, the anionic modification could stabilize them although the functionalized anionic groups may be lost during the reaction. [22] Furthermore, anionic modifying groups can also influence the surface properties of catalysts such as wettability/aerophobicity, which is another aspect of the progress in the OER activity and durability.…”