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

Abstract

High-entropy alloys (HEAs) provide unprecedented physicochemicalproperties over unary nanoparticles (NPs). According to the conventionalalloying guideline (Hume–Rothery rule), however, only size-and-structuresimilar elements can be mixed, limiting the possible combinations of alloyingelements. Recently, it has been reported that based on carbon thermal shocks(CTS) in a vacuum atmosphere at high temperature, ultrafast heating/coolingrates and high-entropy environment play a critical role in the synthesis ofHEAs, ruling out the possibility of phase separation. Since the CTS requiresconducting supports, the Joule-heating efficiencies rely on the carbonqualities, featuring difficulties in uniform heating along the large area. Thiswork proposes a photo-thermal approach as an alternative and innovativesynthetic method that is compatible with ambient air, large-area, remoteprocess, and free of materials selection. Single flash irradiation on carbonnanofibers induced momentary high-temperature annealing (>1800 °C within20 ms duration, and ramping/cooling rates >104 K s−1 ) to successfullydecorate HEA NPs up to nine elements with excellent compatibility forlarge-scale synthesis (6.0 × 6.0 cm2 of carbon nanofiber paper). Todemonstrate their feasibility toward applications, senary HEA NPs(PtIrFeNiCoCe) are designed and screened, showing high activity(𝜼overall = 777 mV) and excellent stability (>5000 cycles) at the water splitting,including hydrogen evolution reactions and oxygen evolution reactions.