Metastable Nickel Carbide Enables Programmable Evolution of Nanoporous Carbon Architectures

Designing nanoporous carbon materials with controllable structure and functionality is a central challenge for electrochemical energy storage. Here we demonstrate metastable Ni₃C as a transformable scaffold enabling programmable synthesis of nanoporous carbon architectures through pathway-dependent structural evolution. Starting from a bicontinuous nanoporous Ni₃C framework, metastability arising from weak Ni-C bonding permits controlled transformation via thermal decomposition, chemical dealloying, and cyclic carbide-metal-carbide evolution, yielding mesoporous graphene (MG), hierarchical nanoporous amorphous carbon (np-C), and an integrated MG/np-C composite, respectively. These pathways preserve mesoscale structural continuity while directing carbon reconstruction toward graphitic or amorphous configurations, producing distinct pore hierarchies, carbon ordering, and electronic transport properties. As electrodes for supercapacitors and sodium-ion batteries, MG provides highly conductive networks, np-C offers micropore-rich structures with high charge-storage density, whereas the MG/np-C composite integrates these complementary attributes to deliver enhanced electrochemical performance. This work establishes metastable phase mediation as a pathway-controlled strategy for engineering nanoporous carbon architectures and related functional materials.