Construction of Fe‐doped NiS–NiS₂ Heterostructured Microspheres Via Etching Prussian Blue Analogues for Efficient Water‐Urea Splitting

Abstract

Developing efficient and robust non‐precious‐metal‐based catalysts to accelerate electrocatalytic reaction kinetics is crucial for electrochemical water‐urea splitting. Herein, Fe‐doped NiS–NiS2 heterostructured microspheres, an electrocatalyst, are synthesized via etching Prussian blue analogues following a controlled annealing treatment. The resulting microspheres are constructed by mesoporous nanoplates, granting the virtues of large surface areas, high structural void porosity, and accessible inner surface. These advantages not only provide more redox reaction centers but also strengthen structural robustness and effectively facilitate the mass diffusion and charge transport. Density functional theory simulations validate that the Fe‐doping improves the conductivity of nickel sulfides, whereas the NiS–NiS2 heterojunctions induce interface charge rearrangement for optimizing the adsorption free energy of intermediates, resulting in a low overpotential and high electrocatalytic activity. Specifically, an ultralow overpotential of 270 mV at 50 mA cm−2 for the oxygen evolution reaction (OER) is achieved. After adding 0.33 M urea into 1 M KOH, Fe‐doped NiS–NiS2 obtains a strikingly reduced urea oxidation reaction potential of 1.36 V to reach 50 mA cm−2, around 140 mV less than OER. This work provides insights into the synergistic modulation of electrocatalytic activity of non‐noble catalysts for applications in energy conversion systems.

(NiFeCu)3S2@(NiFeCu)O Core-Shelled Heterostructure Having Dual-Anion Vacancies for Stable, High-Efficiency Urea Oxidation Reaction

“…To the best of our knowledge, this new UOR catalyst has not been reported. Fe and Cu are used as dopants because they accelerate the electron transfer from Ni to Fe and/or Cu, thus promoting the formation of high Ni-oxidation state for facile UOR. − Here, we show that the long-term stability is therefore enhanced. The dual anion vacancies of Vs and Vo were found to control the charge transfer and intermediate species adsorption resistance, respectively.…”

In situ growth of Prussian blue analogue-derived Fe-doped NiS on Ni(OH)2 for efficient hydrogen evolution reaction

“…The lower overpotential and the smaller Tafel slope of Fe-NiS/Ni(OH) 2 /CC indicate a higher HER activity. In the same conditions (10 mA cm −2 and 1 M KOH), compared with most nickel-based HER electrocatalysts, the performance of Fe-NiS/Ni(OH) 2 /CC is close to and even superior to them, such as Ni 3 S 2 @Ni(OH) 2 (237 mV), 43 Fedoped NiS 2 (198 mV), 44 Fe-NiS/H-3 (196 mV), 45 Fe-doped NiCo 2 S 4 (181 mV), 46 Fe-doped NiS-NiS 2 (162 mV), 13 FeS/NiS/NF (144 mV), 47 FeS/Ni 3 S 2 @NF (130 mV), 10 Fe-NiS 2 (121 mV), 48 and Fe-NiS 2 /MoS 2 (120 mV) 49 (Fig. 8c).…”

“…In recent years, electron modulation and crystal regulation were used widely to enhance the electrocatalytic activity of nickel sulfide. 8,13 In particular, the method of controlling the electron's structure through heteroatomic doping has been proven to be efficient and has produced some favourable achievements. For example, Liu et al 14 reported Cr-doped NiS x grown in situ on nickel foam, which exhibits an excellent hydrogen evolution reaction activity with an overpotential of 81 mV at 10 mA cm −2 .…”

(Fe, F) co-doped nickel oxyhydroxide for highly efficient oxygen evolution reaction

“…4,5 The past decades had witnessed signicant progresses in developing earth-abundant OER electrocatalysts. It was found that a number of non-precious metal (Ni, Co, and Fe) compounds, such as oxides, [6][7][8] hydroxides, [9][10][11] nitrides, [12][13][14] phosphides, [15][16][17] suldes, [18][19][20] and borides, 21,22 possess high and stable OER activities in alkaline media, even surpassing precious metal-based catalysts. It has been well established that non-precious metal compounds would transform into catalytically active oxyhydroxides on the catalyst surface under OER conditions, regardless of material type.…”