We have identified three novel metal phthalocyanine (MPc, M = Mo, Re, and Tc) single-atom catalyst candidates with excellent predicted performance for the production of ammonia from electrocatalytic nitrogen reduction reaction (NRR) through a combination of high-throughput screening and first-principles calculations on a series of 3d, 4d, and 5d transition metals anchored onto extended Pc monolayer catalysts. Analysis of the energy band structures and projected density of states of N 2 -MPc revealed significant orbital hybridization and charge transfer between the adsorbed N 2 and catalyst MPc, which accounts for the high catalytic activity. Among 30 MPc catalysts, MoPc and TcPc monolayers were found to be the most promising new NRR catalysts, as they exhibit excellent stability, low onset potential, and high selectivity. A comprehensive reaction pathway search found that the maximum free energy changes for the MoPc and TcPc monolayers are 0.33 and 0.54 eV, respectively. As a distinctive nature of this work, the hybrid reaction pathway was considered extensively and searched systematically. The onset potential of the hybrid pathway is found to be smaller than or comparable to that of the commonly known pure pathway. Thus, the hybrid path is highly competitive with low onset potential and high activity. The hybrid pathway is expected to have an important impact on future research on the mechanism of NRR, and it will open up a new way to explore the mechanism of the NRR reaction. We hope that our work will provide impetus to the creation of new catalysts for reduction of N 2 to NH 3 . This work provides new insights into the rational design of NRR catalysts and explores novel reaction pathways under ambient or mild conditions.

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A B S T R A C TThe genus Pseudo-nitzschia has attracted attention because of production of the toxin, domoic acid (DA), causing Amnesic Shellfish Poisoning (ASP). Pseudo-nitzschia blooms occur frequently in Chinese coastal waters, and DA has been detected in several marine organisms, but so far no Pseudo-nitzschia strains from Chinese waters have been shown to produce DA. In this study, monoclonal Pseudo-nitzschia strains were established from Chinese coastal waters and examined using light microscopy, electron microscopy and molecular markers. Five strains, sharing distinct morphological and molecular features differentiating them from other Pseudo-nitzschia species, represent a new species, Pseudo-nitzschia simulans sp. nov. Morphologically, the taxon belongs to the P. pseudodelicatissima group, cells possessing a central nodule and each stria comprising one row of poroids. The new species is characterized by the poroid structure, which typically comprises two sectors, each sector located near opposite margins of the poroid. The production of DA was examined by liquid chromatography tandem mass spectrometry (LC-MS/MS) analyses of cells in stationary growth phase. Domoic acid was detected in one of the five strains, with concentrations around 1.05-1.54 fg cell À1. This is the first toxigenic diatom species reported from Chinese waters.

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To explore the species diversity and toxin profile of Pseudo‐nitzschia, monoclonal strains were established from Chinese southeast coastal waters. The morphology was examined under light and transmission electron microscopy. The internal transcribed spacer region of ribosomal DNA was sequenced for phylogenetic analyses, and the secondary structure of ITS2 was predicted and compared among allied taxa. A combination of morphological and molecular data showed the presence of two new species, Pseudo‐nitzschia hainanensis sp. nov. and Pseudo‐nitzschia taiwanensis sp. nov. Pseudo‐nitzschia hainanensis was characterized by a dumpy‐lanceolate valve with slightly blunt apices and a central nodule, as well as striae comprising two rows of poroids. Pseudo‐nitzschia taiwanensis was characterized by a slender‐lanceolate valve, and striae comprising one row of split poroids. The poroid structure mainly comprised two sectors. Both taxa constituted their own monophyletic lineage in the phylogenetic analyses inferred from ITS2 rDNA and were well differentiated from other Pseudo‐nitzschia species. Morphologically, P. hainanensis and P. taiwanensis could be assigned to the Pseudo‐nitzschia delicatissima and the Pseudo‐nitzschia pseudodelicatissima complex, respectively. Particulate domoic acid was measured using liquid chromatography coupled with tandem mass spectrometry (LC‐MS/MS), but no detectable pDA was found. With the description of the two new species, the species diversity of genus Pseudo‐nitzschia reaches 58 worldwide, among which 31 have been recorded from Chinese coastal waters.