Flash-Thermal Shock Synthesis of High-Entropy Alloys Toward High-Performance Water Splitting

High-entropy alloys (HEAs) provide unprecedented physicochemical properties over unary nanoparticles (NPs). According to the conventional alloying guideline (Hume-Rothery rule), however, only size-and-structure similar elements can be mixed, limiting the possible combinations of alloying elements. Recently, it has been reported that based on carbon thermal shocks (CTS) in a vacuum atmosphere at high temperature, ultrafast heating/cooling rates and high-entropy environment play a critical role in the synthesis of HEAs, ruling out the possibility of phase separation. Since the CTS requires conducting supports, the Joule-heating efficiencies rely on the carbon qualities, featuring difficulties in uniform heating along the large area. This work proposes a photo-thermal approach as an alternative and innovative synthetic method that is compatible with ambient air, large-area, remote process, and free of materials selection. Single flash irradiation on carbon nanofibers induced momentary high-temperature annealing (>1800 degrees C within 20 ms duration, and ramping/cooling rates >10(4) K s(-1)) to successfully decorate HEA NPs up to nine elements with excellent compatibility for large-scale synthesis (6.0 x 6.0 cm(2) of carbon nanofiber paper). To demonstrate their feasibility toward applications, senary HEA NPs (PtIrFeNiCoCe) are designed and screened, showing high activity (eta(overall) = 777 mV) and excellent stability (>5000 cycles) at the water splitting, including hydrogen evolution reactions and oxygen evolution reactions.

Automated summary

High-entropy alloys (HEAs) have unique physicochemical properties compared to unary nanoparticles (NPs). Conventional alloying guidelines limit the possible combinations of alloying elements, but recent research has shown that carbon thermal shocks (CTS) and a high-entropy environment play a critical role in HEA synthesis. This study proposes a photo-thermal approach using carbon nanofibers to successfully synthesize HEA NPs with up to nine elements, demonstrating high activity and stability in water splitting reactions.