Mitigating global warming requires innovative development of materials solutions. Intermittent electricity (e.g., generated from wind or solar power), which cannot be stored for more than few hours due to limited grid-scale battery capacity, can be converted into chemical energy. In this context, hydrogen production from electrocatalytic water splitting or carbon dioxide reduction rise as promising candidates, despite the technology implementation being hindered by limited performance and high cost. The main reason of the poor performance is the inefficient electrocatalyst design, such as catalysts used at the anode or cathode sides for the Oxygen Evolution Reaction (OER) or Hydrogen Evolution Reaction (HER), respectively. Noble metals (e.g., Pt, Ir or Ru) are being used as OER/HER catalysts commercially. Despite being very expensive, they still do not provide the necessary level of robustness where their stability is two-three orders of magnitude shorter than the desired lifetime for practical applications.

Extensive research efforts have been presented in literature with an emphasis on replacing noble metal catalysts with less expensive elements (e.g., transition metals) as electrocatalysts for electrocatalytic OER. Nickel based materials (e.g., nickel layered hydroxide) have shown a great enhancement in catalyzing OER at lower overpotentials compared to noble metal catalysts. Alloying of other transition metals (e.g., Mn or Co) with Ni showed an enhanced performance where reaction kinetics is further improved due to optimized interaction between reaction intermediates and NiCo/NiMn catalysts surfaces. Similar observations have been shown for Ni-Fe compounds. Increasing the alloying order (i.e., mixing of three or more elements) influenced the performance positively. Nevertheless, the process of high order alloying turns tedious, complicated and with a very low control over alloying degree. Conventional synthesis methods (e.g., wet chemistry or high temperature annealing) require long time to process (10s of hours to days). Yet, the processes are governed by thermodynamics rules (e.g., valence, atomic radii, crystal structures of the alloying elements), which may result in phase segregation, instead of a complete uniform alloying. In addition, despite computational methods have undergone an immense growth, experimental research has so far benefitted minimally from them due to slow experimental setups.

In the presented talk, we are introducing novel extreme processing synthesis techniques, which enables the stabilization of metastable phases by empowering the kinetics of the process to overcome the limited thermodynamics rules. Kinetics control is achieved by rapid cycling of temperature within milliseconds range from room temperature to elevated degrees (> 1000 C). We demonstrated different technologies to synthesize high entropy alloy (HEA) nanocatalysts for electrocatalytic reactions related to hydrogen generation, carbon dioxide reduction and fuel cells. Modulating the chemistry of HEAs nanoparticles influence their electrocatalytic activity, by promoting the formation of different oxidation states for each element of the HEA material. In addition to demonstrating higher activity, with successful fine tuning of HEA chemistry, we developed non-noble metals electrocatalysts with two orders of magnitude longer stability than state-of-the-art commercial noble metal catalysts. In the presented talk we are delivering insights about the origins of activity enhancement and stability, which will enrich the scientific discussion, to rationally tailor the design of energy materials for many electrocatalytic reactions.