Improving electrocatalytic hydrogen evolution through Co and Ni single atom sites with synergistic effects anchored on carbon foam as a self-supporting electrode

Developing a new type of high-loaded single atom catalysts to further improve the performance of electrocatalytic hydrogen evolution reaction (HER) is still a major challenge. However, multiple single atom sites with synergistic effect between different atoms can promote catalytic activity. In this work, we develop a strategy based on inkjet printing-pyrolysis to anchor Co and Ni single atom sites on carbon foam substrate to form CoNi-N/CMF self-supporting electrode, which shows outstanding electrocatalytic hydrogen evolution performance. Aberration-corrected transmission electron microscopy revealed the coexistence of well dispersed Co and Ni single atoms with atomic distance of 5.3 Å, indicating part of Co and Ni single atoms are indirect bonding between the two atoms. CoNi-N/CMF showed impressive overpotential of 32.6 and 36.6 mV to reach a current density of 10 mA cm⁻² under acidic and alkaline conditions, respectively, which is lower than that of Co or Ni single atoms. Density functional theory calculations revealed that the non-bonding configuration between the two metal atoms forms a synergistic effect to accelerate H* adsorption and desorption, thus optimizing the HER process. This paper provides a new method for the development of single atom catalysts.