Polymeric carbon nitride supported single-phase Ni with exceptional catalytic effect on MgH2 for hydrogen storage

Abstract

Magnesium hydride (MgH₂) with its high hydrogen storage capacity (7.6 wt%) and exceptional reversibility, has emerged as a promising solid-state hydrogen storage material. This study designed a polymeric carbon nitride (PCN) supported single-phase Ni catalyst with superior thermal stability and catalytic activity. The optimized PCN-Ni catalyst significantly reduced the initial dehydrogenation temperature of MgH₂ to 192 ºC. At 295 ºC, the composite released 6.10 wt% H₂ within 5 min, and it subsequently absorbed 5.50 wt% H₂ within 5 min at 150 ºC. Compared to pristine MgH₂, the activation energies for dehydrogenation and hydrogen absorption were reduced by 31.6% and 29.4%, respectively. Moreover, the MgH₂ + 10 wt% PCN-Ni composite exhibited remarkable cycling stability, with capacity retention rates of 96.0% and 96.7% after 20 hydrogenation/dehydrogenation cycles. In conclusion, this work provides a new perspective on the heterogeneous synergy of transition metal and carbon nitride composite catalysts in promoting the dehydrogenation/rehydrogenation reactions of MgH₂ and lays the foundation for the design and fabrication of highly efficient catalysts in other energy storage related fields.