Relevance of metal (Ca versus Mn) embedded C₂N for energy-storage applications: Atomic-scale study

The suitability of embedding metal atoms (Ca versus Mn) in the pores of C₂N to be employed as the anode material for metal-ion battery applications is studied using density-functional theory. The effect of single-atom catalyst (SAC) versus dimer-atom catalyst (DAC) on the uptake catalyst capacity is put under focus. Our results show that both metal atoms exhibit very strong interactions with the pyridinic-nitrogen pore and show the ability of the pore to accommodate either a single Ca atom or a dimer of Mn atoms within its membrane-plane. While the theoretical irreducible capacitance in case of SAC Ca catalyst is limited to about 200 mAhg⁻¹, it can exceed this value in case of DAC-Mn catalyst to reach 1110 mAhg⁻¹. Regarding the adsorption, the H₂ molecule exhibits strong physisorption on Ca-catalyst and moderate chemisorption on Mn-catalyst, with an adsorption energy increasing from SAC to DAC cases. The SAC of Mn is found not only concurrent candidate to Ca for energy-storage applications but further promising for platform of reusable hydrogen gas-sensors with very low recovery time (i.e., τ « 1 s). Our findings are in good agreement with the available experimental data and theoretical results.