Controllable Synthesis of Metastable Nanoparticle Catalysts by Femtosecond Lasers: Reduction Dynamics and Electrocatalytic Applications

ABSTRACT Femtosecond laser‐driven synthesis provides a versatile method for producing nanoparticles with high purity and compositional tunability, suitable for applications in catalysis and nanomanufacturing. However, conventional kinetic models typically treat reactions as continuous, overlooking the pulsed nature of laser excitation, thereby constraining their applicability in directing experimental synthesis. In this study, we established a femtosecond laser‐induced strategy for nanostructures by dividing the processing timeline into pulse‐on and pulse‐off phases to elucidate nanoparticle formation dynamics. Nanoparticle generation encompasses two principal processes: Ultrafast reduction and nucleation ( k 1 ) primarily during pulse‐on phases, and growth ( k 2 ) across both phases. Mass spectrometry further revealed the evolution of solution species in a representative metal precursor system. Employing this framework, we adjusted laser repetition rate to modulate pulse‐on proportion. Higher repetition rates increased k 1 , boosting nucleation and yielding smaller nanoparticles. Lower rates favored k 2 , producing larger particles. This methodology was extended to synthesize diverse monometallic, bimetallic, and high‐entropy nanoparticles across various elements and substrates, as demonstrated by their applicability in representative electrocatalytic reactions, including CO 2 reduction and hydrogen evolution. This work offers a mechanistic basis connecting laser parameters, pulsed dynamics, and nanoparticle properties, promoting rational ultrafast laser nanomaterial design for a wide range of metal and alloy systems.