Synergistic effect of mechanical strain and interfacial-chemical interaction for stable 1T-WSe2 by carbon nanotube and cobalt

Phase-selective synthesis of stable metallic 1T transition metal dichalcogenides (TMDs) is challenging. Herein, we in-situ synthesis of stable 1T cobalt-doped tungsten selenide/carbon nanotubes (Co-WSe2/CNTs) by synergistic effect of mechanical strain and interfacial-chemical interaction by CNTs and Co. Our experimental results indicate that Co-doping is pivotal for conformal coating of 1T Co-WSe2 nanosheets around the CNTs due to their strong interfacial-chemical interaction between Co and CNTs, which is prerequisite for 1T phase engineering with high-stability by mechanical curvature strain. More importantly, for the first time we can easily regulate the concentrations of 1T Co-WSe2 from 67.2% to 82.9% by varying the CNTs curvatures due to the tunable mechanical strains. The single-walled CNTs (SWNTs) with the largest curvature strain induces the highest content of 1T phase in Co-WSe2 (82.9%), and moreover the 1T phase still remains even after high temperature annealing. Further benefiting from the improved electronic properties, the 1T Co-WSe2/SWNTs exhibits enhanced electrocatalytic hydrogen evolution reaction (HER) activity in both acidic and alkaline electrolytes. The present work highlights the important role of strain in the 1T phase formation, also sheds lights on how the 1T phase occurs and stabilizes.