2H–2M Phase Control of WSe2 Nanosheets by Se Enrichment Toward Enhanced Electrocatalytic Hydrogen Evolution Reaction

• Published in: Advanced materials (Weinheim) 2024-02, Vol.36 (8), p.e2307867-n/a
• Main Authors: Kwon, Ik Seon, Kwak, In Hye, Kim, Ju Yeon, Lee, Seung Jae, Sial, Qadeer Akbar, Ihsan, Junaid, Lee, Kug‐Seung, Yoo, Seung Jo, Park, Jeunghee, Kang, Hong Seok
• Format: Article
• Language: English
• Subjects: 2M phase; Catalytic activity; Electronic structure; Fine structure; First principles; Gibbs free energy; hydrogen evolution reaction; Hydrogen evolution reactions; in situ XAFS; Nanosheets; Phase control; Scanning transmission electron microscopy; Se enrichment; spin‐polarized density functional theory; Stacking sequence (composite materials); Substitution reactions; Transition metal compounds; WSe2 nanosheets
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202307867

The phase control of transition metal dichalcogenides (TMDs) is an intriguing approach for tuning the electronic structure toward extensive applications. In this study, WSe2 nanosheets synthesized via a colloidal reaction exhibit a phase conversion from semiconducting 2H to metallic 2M under Se‐rich growth conditions (i.e., increasing the concentration of Se precursor or lowering the growth temperature). High‐resolution scanning transmission electron microscopy images are used to identify the stacking sequence of the 2M phase, which is distinctive from that of the 1T′ phase. First‐principles calculations employing various Se‐rich models (intercalation and substitution) indicated that Se enrichment induces conversion to the 2M phase. The 2M phase WSe2 nanosheets with the Se excess exhibited enhanced electrocatalytic performance in the hydrogen evolution reaction (HER). In situ X‐ray absorption fine structure studies suggested that the excess Se atoms in the 2M phase WSe2 enhanced the HER catalytic activity, which is supported by the Gibbs free energy (ΔGH*) of H adsorption and the Fermi abundance function. These results provide an appealing strategy for phase control of TMD catalysts. Se‐rich WSe2 nanosheets are synthesized via a colloidal reaction and show a 2H–2M phase conversion and enhanced electrocatalytic performance in the hydrogen evolution reaction.