Cooperative electrocatalytic N2 reduction based on WS2-covered Co9S8 hexagonal heterostructures derived from ZIF-67@POMs. (April 2023)

• Record Type: Journal Article
• Authors: Wang, Xinming; Li, Gang; Wang, Chenglong; Rong, Shuang; Pang, Haijun; Ma, Huiyuan; Tian, Yu; Li, Shaobin; Gao, Keqing
• Is Part Of: Materials today energy. Volume 33(2023)
• Publication Date: 2023-04
• Subjects: Polyoxometalates -- Polyacid derivative -- Metal organic frameworks -- Bimetallic sulfide -- S-vacancies; Energy development -- Periodicals; Energy industries -- Periodicals; Power resources -- Periodicals; Energy policy -- Periodicals; Energy development; Energy industries; Energy policy; Power resources; Electronic journals; Periodicals; 621.042
• DOI: 10.1016/j.mtener.2023.101278
• Languages: English
• ISSNs: 2468-6069

Abstract

Abstract: Electrochemical N2 reduction reaction (NRR) to produce NH3 at ambient conditions is a promising route to replace the energy-intensive Haber–Bosch process, but electrochemical NRR with satisfied efficiency remains challenging. Therefore, a number of efforts have been committed to develop high-performance NRR electrocatalysts for highly efficient NH3 synthesis. Herein, Co9 S8 nanosheets with a WS2 outer layer (Co9 S8 @WS2 ) are designed and prepared from ZIF-67@polyoxometalates (polyoxometalates, H3 PW12 O40 ·xH2 O) and used for NRR at ambient temperature and pressure. The successful introduction of S-vacancies can adjust the electronic structure of the material by forming a electron-deficient environment, can make N2 molecules easily adsorbed and activated on the W active site of the catalyst surface, and thus, can promote the electrocatalytic NRR activity of the catalyst. In 0.1 M KOH, the optimized Co9 S8 @WS2 -900 exhibits enhanced Faradaic efficiency (46.81%) and good NH3 yield (50.25 μg h −1 mgcat. −1 ) at −0.4 V vs. a reversible hydrogen electrode, exceeding many recently reported cobalt- or tungsten-based materials. The superior electrocatalytic activity is attributed to the unique composite structures and synergistic effect of electronic couplings between Co9 S8 and sulfur-rich vacancies WS2 . A density functional theory calculation indicates that the inert N2 can be activated by bare W atoms on the rim of the S-vacancies in Co9 S8 @WS2 . The protonation of N2 to form N–NH∗ species is the potential-limiting step (ΔG = 1.05 eV). Therefore, the unique bimetallic sulfide clad architecture and rich S vacancies of Co9 S8 @WS2 provide the reference and inspiration for better designing of high-efficiency nitrogen-fixing catalysts. Graphical abstract: Image 1 Highlights: The Co9 S8 @WS2 bimetallic composites with enriched S-vacancies. This catalyst combines the characteristics of a multi-interface synergy and electron-deficient environment. The Co9 S8 @WS2 -900 displays an ammonia yield rate of 50.25 μg h −1 mgcat. −1 and Faradic efficiency of 46.81% at −0.4 V vs. reversible hydrogen electrode . The density functional theory calculations reveal that the inert N2 can be activated by bare W atoms on the rim of S-vacancies.