A hollow Ni–Fe–B nanochain is successfully synthesized by a galvanic replacement method using a Fe–B nanocomposite and a NiCl2 solution as the template and additional reagent, respectively. Both the concentration of Ni and the morphology of the resulting Ni–Fe–B alloy are controlled by varying the duration of the replacement process during the synthesis. The Ni–Fe–B sample synthesized for 60 min (Ni–Fe–B-60) shows the best catalytic activity at 313 K, with a hydrogen production rate of 4320 mL min−1 gcat−1 and an activation energy for the NaBH4 hydrolysis reaction of 33.7 kJ mol−1. The good performance of Ni–Fe–B-60 towards the hydrolysis of NaBH4 can be ascribed to both hollow nanochain structural and electronic effects. Furthermore, the effects of temperature, catalyst amount, and concentration of NaOH and NaBH4 on the hydrolysis process are systematically studied, and an overall kinetic rate equation is obtained. The hollow Ni–Fe–B nanochain catalyst also shows good reusability characteristics and maintained its initial activity after 5 consecutive cycles.
Amorphous electrocatalysts display several unique advantages in electricity-driven water splitting compared to their crystalline analogs, but understanding their structure–activity relationships remains a major challenge. Herein, we show that the d- and p-electronic states of amorphous Ni-Fe-B can be subtly manipulated by varying the Ni and Fe contents. The optimal Ni-Fe-B alloy exhibits a high performance in the oxygen evolution reaction (OER), as supported by its impressive stability (no clear degradation after 100 h) and considerably lower overpotential compared to those of its crystalline analogs. Based on theoretical calculations, different Ni and Fe contents can cause significant shifts in the d-band levels of Ni and Fe and the p-band level of B, thus altering the OER activity. Additionally, the energy difference between the d- and p-band centers (ΔE ad-p ) may be an effective index for use in reflecting the structure–activity relationship of an amorphous Ni-Fe-B alloy in the OER. An amorphous Ni-Fe-B alloy with a smaller ΔE ad-p displays a higher intrinsic activity. This study supplies a unique direction for use in constructing the structure–activity relationships of amorphous electrocatalysts by revealing the role of ΔE ad-p , which promotes fundamental research and the practical application of amorphous electrocatalysts.
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