Nitrogen substitution of bilayer penta-carbides: high solar-to-hydrogen conversion efficiency and excellent electrocatalytic activity for water splitting.

The shortage of fossil energy and environmental crises are two important issues in the 21st century, and the search for alternatives to fossil fuels, H, is crucial. Herein, based on penta-germagraphene p-GeC, bilayer penta-carbides of p-GeC and nitrogen substituted materials p-GeNC are proposed. The results indicate that gradually replacing the carbon atoms on the surface of p-GeC with nitrogen atoms can change the surface activities and electronic structures, and this is beneficial for both photocatalysis and electrocatalysis. The vertical intrinsic electric field in the two-dimensional materials can enhance photocatalytic water splitting of p-GeC/GeNC and break the conventional limitation of 1.23 eV for the band gap of photocatalysts. Therefore, solar energy conversion efficiency can reach 31%. The smaller effective mass and deformation potential of p-GeC/GeNC along the and directions lead to a huge electron mobility (425.64 × 10 cm V s) at room temperature. Moreover, the overpotential for the hydrogen evolution reaction of p-GeC/GeNC is 0.074 V, which is beneficial for electrocatalysis. The external strain and electric field can also enrich the electronic properties. Surface modification achieved by introducing the nitrogen atoms can improve the catalytic performance of penta-carbides.