Engineering vacancy and hydrophobicity of two-dimensional TaTe2 for efficient and stable electrocatalytic N2 reduction

Abstract

Demand for ammonia continues to increase to sustain the growing global population. The direct electrochemical N2 reduction reaction (NRR) powered by renewable electricity offers a promising carbon-neutral and sustainable strategy for manufacturing NH3, yet achieving this remains a grand challenge. Here, we report a synergistic strategy to promote ambient NRR for ammonia production by tuning the Te vacancies (VTe) and surface hydrophobicity of two-dimensional TaTe2 nanosheets. Remarkable NH3 faradic efficiency of up to 32.2% is attained at a mild overpotential, which is largely maintained even after 100 h of consecutive electrolysis. Isotopic labeling validates that the N atoms of formed NH4+ originate from N2. In situ X-ray diffraction indicates preservation of the crystalline structure of TaTe2 during NRR. Further density functional theory calculations reveal that the potential-determining step (PDS) is ∗NH2 + (H+ + e–) → NH3 on VTe-TaTe2 compared with that of ∗ + N2 + (H+ + e–) → ∗N–NH on TaTe2. We identify that the edge plane of TaTe2 and VTe serve as the main active sites for NRR. The free energy change at PDS on VTe-TaTe2 is comparable with the values at the top of the NRR volcano plots on various transition metal surfaces. Public summary: • 2D TaTe2 is produced in large quantities • Jointly tuning the Te vacancies (VTe) and surface hydrophobicity of 2D TaTe2 enables efficient and stable electrocatalytic NRR with remarkable NH3 faradic efficiency • The edge plane of TaTe2 and VTe serve as the main active sites for NRR • The free energy change at the potential-determining step on VTe-TaTe2 is comparable with the values at the top of the NRR volcano plots on various transition metal surfaces

Keywords

• N2 reduction
• NH3
• electrocatalysis
• TaTe2 nanosheets
• hydrophobicity