Synthesis of Co2FeAl alloys as highly efficient electrocatalysts for alkaline hydrogen evolution reaction

The development of cost-effective non-precious metal electrocatalysts is a major challenge for water splitting applications, but it is important for the realization of renewable energy systems. Alloying has proved an effective way to design metal-based electrocatalysts, and by controlling the annealing temperature, the surface morphology and crystallinity of the alloy can be tuned to control the hydrogen evolution reaction (HER) performance. In this work, with a simple coprecipitation method, we have prepared Co 2 FeAl alloys at different annealing temperatures (550 °C–670 °C), which exhibit excellent crystallinity and electrocatalytic performance for HER in alkaline solution. Among all conditions, the Co 2 FeAl alloys prepared at 620 °C shows the better crystallinity and the higher purity, and it could achieve a low overpotential of 149 mV at 10 mA cm −2 in alkaline solution. The overpotential demonstrates persistent stability with only 3 mV change after over 1000 cycles. Both density functional theory (DFT) calculations and experimental results revealed that alloying optimizes the electronic structure near the Fermi surface of the system, improving the electron transport efficiency and enhancing the catalytic activity. These Co 2 FeAl alloys are appealing candidates for high-performance alkaline HER electrocatalytic electrodes in water electrolysis due to their outstanding electrocatalytic properties. We demonstrate that the efficient electrocatalytic activity is due to high temperature annealing, along with the synergistic effect of alloying, lead to the surface structure and electronic structure of the alloy have changed. This strategy enables the Co 2 FeAl alloy electrocatalyst to achieve a low overpotential of 149 mV at 10 mA cm −2 in alkaline solution. • Co 2 FeAl Alloy is prepared by facile coprecipitation method. • High temperature annealing to adjust the crystal plane orientation of alloys. • It could achieve a low overpotential of 149 mV at 10 mA cm −2 in alkaline solution. • It shows highly efficient electrocatalytic activity for HER while remaining stable/durable. • DFT calculations revealed that it optimizes the electronic structure near the Fermi surface.