Issue 22, 2020

Element table of TM-substituted polyoxotungstates for direct electrocatalytic reduction of nitric oxide to ammonia: a DFT guideline for experiments

Abstract

The electrochemical NO reduction (NOER) is one of the most promising routes for ammonia synthesis and for simultaneously removing the air pollutant, NO. However, the current electro-catalysts are mainly metal based, and the search for new and cost-efficient NOER catalysts is in the pipeline. Polyoxometalates, a class of metal–oxide clusters, exhibiting unique electrochemical redox behavior, have been widely applied to many electrocatalytic processes. In this work, density functional theory (DFT) calculations were adopted to investigate the NOER performance of a series of transition metal-substituted (TMPOMs, FeII ∼ CuII, RuII ∼ AgI, OsII ∼ AuI) heteropolytungstates. Firstly, we take the highly active SiW11FeII catalyst reported in experiments as an example to investigate its detailed NOER mechanism, and thus provide some qualitative criteria for screening potential new NOER catalysts. The *NHO and *NHOH intermediates are confirmed based on their lower energies compared to *NOH and *NH2O, respectively. The high activity and ammonia selectivity of SiW11FeII are dominated by four factors: (i) a moderate NO adsorption ability, (ii) an acceptable N–O bond activation barrier (ΔGb = 0.65 eV) at room temperature, (iii) low onset potential for the potential-limiting step (ca. −0.21 V), and (iv) effective suppression of the competitive HER and N2O formation reaction. Inspired by this, NiII-, CoII-, CuII-, PdII-, PtII-, and AgI-substituted heteropolytungstates are identified as candidate electrocatalysts for application in the NOER through a comprehensive comparison with the SiW11FeII case. Particularly, SiW11NiII was selected as the most optimal with an extremely low ΔGb of only 0.07 eV for the *NO → *NHO step. It is suggested that the high electrocatalytic activity of SiW11NiII originates from its high reduction ability to accept electrons in the electrocatalytic process, and the low basicity strength of O sites to promote the transfer of H. The present work provides an expansion of the POMs’ family in the field of NOER, and ultimately facilitates the designing of nitrogen-cycle catalysts for targeted environmental and synthesis applications.

Graphical abstract: Element table of TM-substituted polyoxotungstates for direct electrocatalytic reduction of nitric oxide to ammonia: a DFT guideline for experiments

Supplementary files

Article information

Article type
Research Article
Submitted
02 محرم 1442
Accepted
13 صفر 1442
First published
14 صفر 1442

Inorg. Chem. Front., 2020,7, 4507-4516

Element table of TM-substituted polyoxotungstates for direct electrocatalytic reduction of nitric oxide to ammonia: a DFT guideline for experiments

Z. Lang, J. Miao, H. Tan, Z. Su, Y. Li and Z. Zheng, Inorg. Chem. Front., 2020, 7, 4507 DOI: 10.1039/D0QI01014F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements