Simple construction of ruthenium single atoms on electrospun nanofibers for superior alkaline hydrogen evolution: A dynamic transformation from clusters to single atoms.

• Ru SAs were in situ synthesized by the dynamic transformation from clusters. • The formation of Ru–N–C bonds plays an important role for anchoring the Ru SAs. • The transformation can be controlled by the treatment time and temperatures. • Ru SAs exhibit superior HER activity with overpotential of 34 mV (20 mA cm−2). The challenges for preparing metal single atoms (MSAs) catalysts are facile synthesis approaches and the suitable supports with strong coordination to stabilize MSAs. Herein, we reported a facile strategy to synthesize the Ru single atoms (Ru SAs) through the dynamic transformation from clusters to single atoms by combining the electrospun technology and NH 3 -assisted graphitization process. The small Ru nanoclusters (NCs) supported on carbon nanofibers (CNFs) were in situ converted into Ru SAs in N-doped CNFs under the NH 3 treatment. Through controlling the NH 3 treatment time and graphitization temperatures, the Ru nanocrystals exhibit a dynamic transformation from nanoclusters to single atoms. The results indicate that the Ru NCs with larger amounts of Ru SAs exhibit superior HER activity in alkaline media with low overpotential of 34 mV at 20 mA cm−2, which is even significantly better than commercial Pt/C catalysts. The mass activity of Ru SAs/NCNFs is about 390 A g−1 Ru at an overpotential of 100 mV, which is ~3.5 times higher than that of commercial Pt/C (110 A g−1 Pt). This strategy will provide a new way for the large-scale production of MSAs transformed from different metal nanoparticles or nanoclusters. [ABSTRACT FROM AUTHOR]