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 was 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 synthesis of HEAs, ruling out 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. In this work, we propose 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 (> 1,800°C within 20-ms duration, and ramping/cooling rates > 10 4 K/s) to successfully decorate HEA NPs up to 9 elements with excellent compatibility for large-scale synthesis (6.0 × 6.0 cm 2 of carbon nanofiber paper). To demonstrate their feasibility toward applications, senary HEA NPs (PtIrFeNiCoCe) were designed and screened, showing high activity (η overall = 777 mV) and excellent stability (>5,000 cycles) at the water splitting, including hydrogen evolution reactions and oxygen evolution reactions. This article is protected by copyright. All rights reserved.