The carbon content in HP-MoOC was further increased through additional methane plasma treatment during PECVD (see details in Supplementary Materials). The resulting product was denoted as HCP-MoOC and still maintained the nanoedge-enriched morphology (Figure ). The vertically standing morphology of HCP-MoOC was verified through the crosssectional scanning electron microscope (SEM) image (Figure ), and the elemental mappings obtained by EDX confirmed the uniform distribution of Mo, C, and O elements within the HCP-MoOC. The Mo:O:C atomic ratio of HCP-MoOC was determined to be 1:1:3 (Supplementary Figure ).