Tao Sun
Email Address
chmst@nus.edu.sg
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Publication Chemical Design and Synthesis of Superior Single-Atom Electrocatalysts via In-Situ Polymerization(Royal Society of Chemistry (RSC), 2020-07-27) Xu, Haomin; Xi, Shibo; Li, Jing; Liu, Shikai; Lyv, Pin; Yu, Wei; SUN TAO; Qi, Dong-Chen; HE QIAN; Xiao, Hai; Lin, Ming; Wu Jishan; Zhang Jia; LU JIONG; Dr He Qian; CHEMISTRY; MATERIALS SCIENCE AND ENGINEERINGMolecule-like electrocatalysts with FeN4 motifs have been demonstrated to be excellent candidates for various renewable energy conversions. The ability to further tune the electronic properties of molecular FeN4 motifs and integrate them onto conductive supports represents a key step towards the synthesis of highly robust and efficient single-atom catalysts (SACs) for practical applications. Here, we developed a new route for the synthesis of well-defined single-atom FeN4 electrocatalyst via in-situ polymerization of four amino groups functionalized iron phthalocyanine (NH2-FePc) molecules on conductive carbon nanotubes. The intermolecular oxidative dimerization between amino groups of NH2-FePc creates the desired electron-withdrawing pyrazine linker between FeN4 motifs, which can significantly optimize their electrocatalytic performances. As a result, FeN4-SAC exhibits both outstanding ORR activity (a half-wave potential of 0.88 V vs. RHE) and excellent performance in Zn-oxygen battery, outperforming the commercial Pt/C and pristine iron phthalocyanine (FePc) catalysts. Our theoretical calculations reveal that the presence of electron-withdrawing linkers shifts the occupied antibonding states towards lower energies and thus weakens the Fe-O bond, which is primarily responsible for the enhancement of ORR activity.Publication Engineering the Electronic Structure of MoS2 Nanorods by N and Mn Dopants for Ultra-Efficient Hydrogen Production(AMER CHEMICAL SOC, 2018-08-01) Tao Sun; Jun Wang; Xiao Chi; Yunxiang Lin; Zhongxin Chen; Xiang Ling; Chuntian Qiu; Yangsen Xu; Li Song |Wei Chen; Chenliang Su; Prof Chen Wei; CENTRE FOR ADVANCED 2D MATERIALS; CHEMISTRY© 2018 American Chemical Society. Developing economical and efficient electrocatalysts with nonprecious metals for the hydrogen evolution reaction (HER), especially in water-alkaline electrolyzers, is pivotal for large-scale hydrogen production. Recently, both density functional theory (DFT) calculations and experimental studies have demonstrated that earth-abundant MoS2 is a promising HER electrocatalyst in acidic solution. However, the HER kinetics of MoS2 in alkaline solution still suffer from a high overpotential (90-220 mV at a current density of 10 mA cm-2). Herein, we report a combined experimental and first-principle approach toward achieving an economical and ultraefficient MoS2-based electrocatalyst for the HER by fine-tuning the electronic structure of MoS2 nanorods with N and Mn dopants. The developed N,Mn codoped MoS2 catalyst exhibits an outstanding HER performance with overpotentials of 66 and 70 mV at 10 mA cm-2 in alkaline and phosphate-buffered saline media, respectively, and corresponding Tafel slopes of 50 and 65 mV dec-1. Moreover, the catalyst also exhibits long-term stability in HER tests. DFT calculations suggest that (1) the electrocatalytic performance can be attributed to the enhanced conductivity and optimized electronic structures for facilitating H∗ adsorption and desorption after N and Mn codoping and (2) N and Mn dopants can greatly activate the catalytic HER activity of the S-edge for MoS2. The discovery of a simple approach toward the synthesis of highly active and low-cost MoS2-based electrocatalysts in both alkaline and neutral electrolytes allows the premise of scalable production of hydrogen fuels.Publication Defect chemistry in 2D materials for electrocatalysis(ELSEVIER SCI LTD, 2019-06-01) Tao Sun; Guoqiang Zhang; Dong Xu; Xu Lian; Hexing Li; Wei Chen; Chenliang Su; Prof Chen Wei; CHEMISTRY© 2019 Elsevier Ltd Two-dimensional (2D) nanomaterials, including metal-free (graphene, carbon nitride, and black phosphorus et al.) and transition metal-based materials (dichalcogenides, oxides, hydroxides, phosphides, and MXenes et al.), have emerged as promising candidates for electrocatalysis due to their unique physical, chemical, and electronic properties. Specifically, 2D materials with ultra-thin thickness usually possess more vacancy-type defects and exposed edges than bulk materials, resulting in different electronic characteristics relative to those of bulk materials and leading to changes in the reactant absorption energy on catalysts. Introducing heteroatom dopants can further alter the charge distribution in 2D materials, thereby facilitating the formation of new defects and catalytic active-sites to improve the electrocatalytic performance. This review highlights recent defect chemistry advances and developments in 2D materials for electrocatalysis. We discuss various defects in 2D materials, such as edge defects, topological defects and vacancy defects so on, and the effects of defects on electrocatalytic performance. Defect engineering and rational design strategies for controlling defects on 2D materials will also be systematically discussed. Finally, various advanced characterization technologies to reveal different types of defects will be discussed.Publication Stable, carrier separation tailorable conjugated microporous polymers as a platform for highly efficient photocatalytic H-2 evolution(ELSEVIER, 2019-05-15) Guoqiang Zhang; Wei Ou; Jun Wang; Yangsen Xu; Dong Xu; Tao Sun; Shuning Xiao; Mengran Wang; Hexing Li; Wei Chen; Chenliang Su; Prof Chen Wei; CHEMISTRY© 2018 Elsevier B.V. The molecular design of highly photo-functional polymers with high charge separation efficiency and wide spectral absorption are long term quest for photocatalysis. Herein, we design and develop a series of nitrogen-containing conjugated microporous polymers (N-CMPs) with tailored donor-acceptor units for enhancing charge separation and light harvesting for visible light photocatalytic H2 production. By alternating the substitution position (o-, m-, or p-) and the number of electron donor (carbazole, diphenylamine) and acceptor (cyano) units on the 3D-core structure, a series of N-CMPs with adjustable donor-acceptor (D-A) charge separation efficiencies and tuneable band gaps in the range of 1.64–2.29 eV were obtained, enabling the precise control of the photocatalytic activity at the molecular level. The optimized N-CMP (4-CzPN) exhibits a higher visible light H2 production rate at 2103.2 μmol/h·g and the apparent quantum yield (AQY) at 420 nm reaches 6.4%. Furthermore, the 4-CzPN photocatalyst maintains excellent durability and recycling performance under 25 h continued light irradiation. The outstanding photocatalytic performance of the optimized N-CMPs with D-A structure is attributed to the enhanced polarity and conjugated degree of their core structure, which promotes charge separation and light absorption.Publication Ferromagnetic single-atom spin catalyst for boosting water splitting(NATURE PORTFOLIO, 2023-07) Sun, Tao; Tang, Zhiyuan; Zang, Wenjie; Li, Zejun; Li, Jing; Li, Zhihao; Cao, Liang; Rodriguez, Jan Sebastian Dominic; Mariano, Carl Osby M; Xu, Haomin; Lyu, Pin; Hai, Xiao; Lin, Huihui; Sheng, Xiaoyu; Shi, Jiwei; Zheng, Yi; Lu, Ying-Rui; He, Qian; Chen, Jingsheng; Novoselov, Kostya S; Chuang, Cheng-Hao; Xi, Shibo; Luo, Xin; Lu, Jiong; Dr Qian He; CHEMISTRY; MATERIALS SCIENCE AND ENGINEERINGHeterogeneous single-atom spin catalysts combined with magnetic fields provide a powerful means for accelerating chemical reactions with enhanced metal utilization and reaction efficiency. However, designing these catalysts remains challenging due to the need for a high density of atomically dispersed active sites with a short-range quantum spin exchange interaction and long-range ferromagnetic ordering. Here, we devised a scalable hydrothermal approach involving an operando acidic environment for synthesizing various single-atom spin catalysts with widely tunable substitutional magnetic atoms (M1) in a MoS2 host. Among all the M1/MoS2 species, Ni1/MoS2 adopts a distorted tetragonal structure that prompts both ferromagnetic coupling to nearby S atoms as well as adjacent Ni1 sites, resulting in global room-temperature ferromagnetism. Such coupling benefits spin-selective charge transfer in oxygen evolution reactions to produce triplet O2. Furthermore, a mild magnetic field of ~0.5 T enhances the oxygen evolution reaction magnetocurrent by ~2,880% over Ni1/MoS2, leading to excellent activity and stability in both seawater and pure water splitting cells. As supported by operando characterizations and theoretical calculations, a great magnetic-field-enhanced oxygen evolution reaction performance over Ni1/MoS2 is attributed to a field-induced spin alignment and spin density optimization over S active sites arising from field-regulated S(p)–Ni(d) hybridization, which in turn optimizes the adsorption energies for radical intermediates to reduce overall reaction barriers.Publication B, N Codoped and Defect-Rich Nanocarbon Material as a Metal-Free Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions(WILEY, 2018-07-01) Sun, Tao; Wang, Jun; Qiu, Chuntian; Ling, Xiang; Tian, Bingbing; Chen, Wei; Su, Chenliang; Prof Chen Wei; CHEMISTRY© 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The development of highly active, inexpensive, and stable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts to replace noble metal Pt and RuO2 catalysts remains a considerable challenge for highly demanded reversible fuel cells and metal–air batteries. Here, a simple approach for the facile construction of a defective nanocarbon material is reported with B and N dopants (B,N-carbon) as a superior bifunctional metal-free catalyst for both ORR and OER. The catalyst is prepared by pyrolyzing the composites of ethyl cellulose and high-boiling point 4-(1-naphthyl)benzeneboronic acid in NH3 atmosphere with an inexpensive Zn-based template. The obtained porous B,N-carbon with rich carbon defects exhibits excellent ORR and OER performances, including high activity and stability. In alkaline medium, B,N-carbon material shows high ORR activity with an onset potential (Eonset) reaching 0.98 V versus reversible hydrogen electrode (RHE), very close to that of Pt/C, a high electron transfer number and excellent stability. This catalyst also presents the admirable ORR activity in acidic medium with a high Eonset of 0.81 V versus RHE and a four-electron process. The OER activity of B,N-carbon is superior to that of the precious metal RuO2 and Pt/C catalysts. A Zn–air battery using B,N-carbon as the air cathode exhibits a low voltage gap between charge and discharge and long-term stability. The excellent electrocatalytic performance of this porous nanocarbon material is attributed to the combined positive effects of the abundant carbon defects and the heteroatom codopants.