Effects of molybdenum content and heat treatment on hydrogen evolution reaction properties and microstructure of FeCoCrNiMox high entropy alloys
Qiankun Zhang, Mengmeng Du, Yifeng Xiao, Liang Wu, Jinwen Qian, Can Zhang, Yuehui He
Abstract
The preparation of efficient and long-lasting electrocatalysts with low cost is crucial for hydrogen production by water electrolysis . Here, a series of high-entropy alloys (HEAs) of FeCoCrNiMo x (x = 0, 0.5, 1, 1.5, and 2) were created by arc melting method and enhanced by heat treatment according to various schedules. The microstructure transitioned from the FCC phase to the FCC + σ phase and finally to the FCC + σ + μ phase with the increase of Mo content . The FeCoCrNiMo 1.5 HEAs performed superior catalytic properties , which could be further modified by solution and aging treatment. As-cast FeCoCrNiMo 1.5 alloy showed a HER overpotential of 344 mV at the current density of 10 mA/cm 2 . After age treated at 800°Cthe overpotential decreased to 260 mV. According to the findings of SEM and TEM , the electrocatalytic activity performance of FeCoCrNiMo 1.5 HEAs after aged at 800 °C might be related to the precipitation of micro/nano-scale FCC phases inside μ phases. This work demonstrates the feasibility of non-noble metal-based HEAs (excluding platinum group metals) for hydrogen evolution and proposes a possible way to further enhance the electrocatalytic performance through heat treatment.