1. Schematic illustration for fabrication procedure of Nd-Ni-B/NF electrocatalysts

2. SEM images of (a) NF and (b,c) 3-NNB/NF, (d) EDX mappings of 3-NNB/NF

3. (a) TEM and (b) HRTEM images of 3-NNB/NF with inset in (b) showing the corresponding SAED pattern

4. XRD patterns of 0-NNB/NF and 3-NNB/NF powders

5. (a) LSV curves, (b) overpotentials at 20 mA∙cm^-2, (c) Tafel curves (derived from (a)) and (d) exchange current densities (j₀) derived from the Tafel curves of x-NNB/NF(x=0, 2, 3, 4, 5) and Pt/C electrodes; (e) CV curves of 3-NNB/NF electrode at different scan rates; (f) Coulomb curves of charge double-layer capacitance of x-NNB/NF(x=0, 2, 3, 4, 5) electrodes

6. Nyquist plots of x-NNB/NF(x=0, 2, 3, 4, 5) electrodes towards HER with inset showing the corresponding equivalent circuit

7. (a) LSV curves and (b) Tafel curves of NNB/NF-y(y=25, 35, 45, 55) electrodes

8. (a-e) CV curves at different scan rates and Coulomb curves of charge double-layer capacitance for NNB/NF-y (y=25, 35, 45, 55) electrodes

9. (a) I-t curve for NNB/NF-35 under 100 mV static overpotential for stability test 12 h; (b) Polarization curves of NNB/NF-35 before and after 2000 CV sweeps; (c) LSV curves and digital photos (insets) of NNB/NF-35 electrodes with different shapes; (d) Comparison of HER activities for different non-noble electrocatalytic materials in alkaline solution

S1. SEM images of x-NNB/NF(x=0, 2, 3, 4, 5)

S2. CV curves at different scan rates for x-NNB/NF(x=0, 2, 3, 4, 5)

S3. (a) SEM image and XRD pattern of 3-NNB/Cu-600 ℃; (b) LSV curves of 3-NNB/Cu and 3-NNB/Cu-600 ℃

S4. Faradaic efficiencies for HER catalyzed by NNB/NF-35 in 1.0 mol∙L^-1 KOH

S5. SEM images of NNB/NF-35(a) before and (b) after the HER measurement for 12 h

Table 1. EIS parameters of x-NNB/NF(x=0, 2, 3, 4, 5) electrodes

Table 2. Comparison of the electrocatalytic HER activity for representative nonprecious HER catalysts in 1.0 mol∙L^-1 KOH electrolyte