Highly exfoliated NiPS3 nanosheets as efficient electrocatalyst for high yield ammonia production

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-02, Vol.430, p.132649, Article 132649
• Main Authors: Vedhanarayanan, Balaraman, Chiu, Cheng-chau, Regner, Jakub, Sofer, Zdenek, Seetha Lakshmi, K.C., Lin, Jeng-Yu, Lin, Tsung-Wu
• Format: Article
• Language: English
• Subjects: Electrocatalysts; Exfoliation; Lithium intercalation; Nitrogen reduction reaction; Transition metal phosphorous trichalcogenides
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.132649

[Display omitted] •Highly exfoliated NiPS3 nanosheets are synthesized from bulk material.•Li-intercalation followed by aqueous exfoliation led to de-stacking of NiPS3 up to bilayers.•Exfoliated NiPS3 exhibited NH3 yield of 118 μg h−1 mgcat-1 and a Faraday efficiency of 17%.•DFT studies revealed an associative mechanism for the nitrogen reduction reaction.•The very first hydrogenation step is found as potential determining step. The development of electrocatalytic nitrogen reduction reaction (NRR) at ambient conditions as an alternative to traditional high-temperature ammonia synthesis is a vibrant research topic due to the potential to significantly reduce the energy consumption required for the production of ammonia. Several noble metal-based materials have already been identified as highly active electrocatalysts for this purpose. However, the development of non-precious metal-based electrocatalysts is necessary for realizing cost-effective ammonia synthesis at large scales. This work has explored the potential of the less exploited transition metal phosphorus trichalcogenide NiPS3 as an NRR electrocatalyst. Excellent NRR activities have been achieved by exfoliating bulk NiPS3 into bi- or tri-layered nanosheets. The NH3 yield attained using exfoliated NiPS3 is 118 μg h−1 mgcat-1 with a Faraday efficiency of > 17 % at an applied potential of −0.4 V vs RHE. The NRR performance of exfoliated NiPS3 in terms of NH3 yield surpasses many non-noble metal-based catalysts reported in the literature. Further, it also exhibited a stable NRR activity of > 90% even after several repetitive cycles. Plane-wave DFT calculations at the GGA + U level have been used to investigate the reaction pathways. It could be shown that the NNR follows an associative mechanism, with the very first hydrogenation step being the potential determining step.