Research groups led by Prof. ZHANG Donghui and Associate Prof. LIU Shu from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences recently revealed Feshbach Resonances in the F+H2O→HF+OH reaction. The results were published in Nature Communications. Feshbach resonances of a chemical reaction are transiently trapped quantum states along the reaction coordinate in the transition-state region. They not only have a profound influence on both the rate and product distribution, but also provide sensitive probes to the potential energy surface (PES) of the reaction.
　　(A)Scattering wave functions；(B)vibrational adiabatic potentials analyses. (Image by LIU Shu) Over the past decades, great efforts have been devoted to detecting resonances in chemical reactions and to studying their structures and dynamics. Through close interactions between theory and experiment, our understanding of Feshbach resonances in triatomic reaction such as the F/Cl+H2 (HD) reactions is now highly sophisticated. One of the major challenges for reaction dynamics is to achieve such sophisticated understanding of systems involving more than three atoms，as the first step is the systems involving four atoms. As a result, the F+H2O reaction has emerged as the benchmark system for such a purpose. Similar to the F+H2 system, the F+H2O→HF+OH reaction is highly exothermic and has a low and “early” barrier on the ground electronic state. There is a relatively deep vanr der Waals (vdw) well in the entrance channel, and a hydrogen bond well in the exit channel. In an earlier photodetchment study of FH2O？, Feshbach resonances have been discovered trapped in the HF-OH interaction well. However, it is not clear if these resonances are accessible by the F+H2O reaction. And how these resonances affect effect the reaction? Recently, the ZHANG’s group performed an accurate state-to-state quantum scattering study of the title reaction by using the time-dependent wave packet method on an accurate newly constructed PES. The total reaction probabilities exhibit many pronounced oscillatory structures especially for collision energy below 0.2 eV. Analysis of scattering wave functions and vibrational adiabatic potentials (VAP) reveal that these oscillating structures originate from the Feshbach resonance states trapped in the HF(v’=2)-OH VAP well, producing mainly HF(v’=1) product. However, different from the F+H2 reaction in which the HF bond softening creates a peculiar well on the H-HF(v’=3) VAP, the VAP well for the F+H2O reaction is mainly hydrogen bond between HF and OH in nature. This work was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences, and DICP. (Text and Image by LIU Shu)

Recently, a research team led by Prof. DENG Dehui from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences and their collaborators have achieved highly efficient H2 production from electrocatalytic decomposition of H2S via a robust graphene encapsulating metal catalyst. It provides a promising way for eliminating pollutant hydrogen sulfide and producing green hydrogen energy. These findings were published as a communication in the Energy & Environmental Science. (Left): Electrocatalytic decomposition of H2S for H2 production via robust chainmail catalyst.
　　(Right): Comparison of sulfide oxidation reaction (SOR) and oxygen evolution reaction (OER) polarization curves for catalyst. The difference value of two reactions’ onset potential is 1.24 V.(Image by ZHANG Mo and GAO Hehua) Hydrogen sulfide is a toxic by-product of oil and gas production released in enormous quantities, and it is also a potential source of an important green energy carrier, namely, hydrogen gas. Based on the Claus process, the current industrial technology for removing H2S only recovered sulfur from H2S, while the hydrogen constituent is wasted as steam. The electrocatalytic decomposition of H2S is a kind of mild and efficient method, which produces hydrogen at the cathode and recycle sulfur at the anode simultaneously. However, this technique is hindered by lacking suitable catalysts, as the reported precious materials are high-cost and the bare non-precious metal materials are easily corroded. Therefore, developing a low-cost, high-efficient and robust electrocatalyst is crucial to achieve a sustainable electrocatalytic decomposition of H2S. Based on the concept of chainmail catalysts which is firstly proposed by DENG’s group, (Angew. Chem. Int. Ed., 2013, 52, 371, Angew. Chem. Int. Ed., 2014, 53, 7023, Energy Environ. Sci., 2014, 7, 1919, Angew. Chem. Int. Ed., 2015, 54, 2100, Nature Nanotech., 2016, 11, 218, Energy Environ. Sci., 2016, 9, 123, Adv. Mater., 2017, 29, 1606967, Adv. Mater., 2019, 31, 1901996), researches from DENG’s group developed a kind of new graphene-encapsulated non-precious metal chainmail material as a low-cost and high activity electrocatalyst for decomposition of H2S. The optimized catalyst drove hydrogen production from decomposing H2S at a much lower potential, which decreases 1.24 V than that of water splitting. Meanwhile, it displayed high activity which is almost twice current density than that of Pt/C, and maintained 500 h stability without decay. Further the reaction active sites were studied by DFT calculations cooperating with Prof. GUAN Jing from Qingdao University of Technology. They demonstrated the superiority of catalyst originates from the modulation of the electronic structure of graphene surface by metal core and nitrogen dopant by the combination of theory and experiment results. To demonstrate the reliability of this catalyst, the researches applied it into the demo of converting H2S from industrial syngas (2% H2S), which couplings the removal of H2S impurities and the production of hydrogen. The chainmail catalyst showed high stability during 1200 h test, indicating its potential for converting waste to sustainable energy in the practical application. In addition, there are a large amount of sulfide existing in the wastewater of paper mill and tannery. The development of this chainmail provides a new idea for electrocatalytic treatment for such kind of industrial wastewater. These works were supported by Ministry of Science and Technology of China, National Natural Science Foundation of China, Key Research Program of Frontier Sciences of the Chinese Academy of Sciences, the DNL Cooperation Fund and Collaborative Innovation Center of Chemistry for Energy Materials (2011. iChEM). (Text and image by ZHANG Mo and GAO Hehua)

A research work done by Prof. WU Zhong-Shuai and Prof. FU Qiang from Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has successfully demonstrated new-concept planar micro-supercapacitors by encapsulating high capacitance electrodes within a robust hydrogel matrix which renders it essentially shapeless, which has been published with the title of “Substrate-Free and Shapeless Planar Micro-Supercapacitors” in the journal Adv. Funct. Mater. Electrochemical energy storage devices (EESDs) are presently at the frontier of clean energy research. However, they have not been able to keep up with the rapid progress in energy generation and consumption devices due to constraints on form factor of the EESDs. Such problems hinder the integration of EESDs with electronics, thus preventing the realization of truly independent, shape-versatile machines. The root cause of this problem is apparently the mechanical incompatible adhesion of different electrodes with electrolyte and the substrate. Moreover, the substrate (typically polymers like poly-ethylene terephthalate, glass, silicon), although being an inactive component contribute most to the total weight and volume of the entire device, thus overshadowing the high performance of two-dimensional active materials and reducing the total energy output of EESDs. Therefore, it is necessary to innovate new architectures for EESDs that will allow the removal of inactive components and maintain high capacitance of devices with ultrathin geometry; thus, promoting superior integration.
　　Substrate-free and shapeless micro-supercapacitors for next-generation electronics (Image by DAS Pratteek) To this end, our scientists WU Zhong-Shuai et. al at DICP, reported a prototype planar and shapeless micro-supercapacitor (SMSC) by encapsulating ultrathin MXene-based electrodes (5 mm) inside thin film hydrogel electrolyte (37 mm) to realize ultraflexible features along with high capacitance output from a single device. The total areal capacitance of 40.8 mF cm-2 is among the highest reported value for MXene-based supercapacitors. Additionally, the flexibility is unparalleled since the device can be bend, folded, spiralled, crumpled and passed through fluid channels, thanks to its ultrathin and shapeless nature. Furthermore, this technology is easily scalable not only to other electrode fabrication methods, but also to different active materials as well. This has been demonstrated by preparing 9 series-connected SMSCs with screen-printed graphene electrodes delivering a 7.2 V while crumpling them from 0.11 to 0.01 cm3 in an extremely deformed state. Such devices hold promises for finally closing the gap between electronics and EESDs for creating independently powered, next-generation nanomachines for a variety of unthinkable applications. This work was supported by National Natural Science Foundation of China, National Key R&D Program of China, CAS-TWAS President’s Fellowship, etc. (Text by DAS Pratteek, HOU Xiaocheng)

A research group led by Prof. WU Kaifeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) recently reported their latest progress on the mechanisms of triplet energy transfer across the inorganic /organic interface. By building model systems with well-defined interfacial energetics based on lead halide perovskite nanocrystals and polycyclic aromatic hydrocarbons (PAHs), and using femtosecond laser spectroscopy, they revealed a unified picture of “charge transfer mediated triplet energy transfer” (CT-mediated TET). The results were recently published on Nat. Commun. 
　　A unified picture of real versus virtual CT-mediated TET mechanisms across the inorganic nanocrystal/organic molecule interface. Molecular spin-triplet states (hereafter called “triplets”) have been an important subject of research in photochemistry for many decades, because of their broad applications ranging from photoredox catalysis to photodynamic therapy and to photon management. These optically “dark” triplets cannot be directly populated using light and needs to be sensitized via a process called triplet energy transfer (TET). Recently inorganic semiconductor nanocrystals (NCs) have emerged as a novel type of triplet sensitizers because of their excellent light-capturing capability and small intersystem crossing energy loss in these NCs. The literature to date, however, is very vague regarding the detailed mechanisms of TET from inorganic NCs to organic molecules. Some studies report a direct, two-electron exchange mechanism (called Dexter mechanism), while other studies show evidence for TET mediated by charge transfer states. There are also claims on NC surface defect states mediated TET. Thus, clarifying the mechanism and even establishing a unified picture is very essential for this field. In recognition of the above-mentioned complexities, the WU group decided to build model systems using highly-emissive lead halide perovskite nanocrystals as the triplet donor and polycyclic aromatic hydrocarbons (PAHs) as the acceptor. The high emissivity of the perovskite NCs help excluding a major impact from surface defect states. The interfacial energetics between the NCs and PAHs are carefully determined in order to predict whether charge transfer is energetically allowed or inhibited. Detailed femtosecond laser spectroscopy studies establish that in the case of tetracene as the acceptor, where hole transfer from NCs to tetracene is energetically favoured, TET is mediated by a real charge separated state, whereas “direct” TET is observed for the naphthalene system because charge transfer processes are energetically uphill. Notably, however, the “direct” TET is also likely mediated through a high-energy, virtual charge-transfer state, because of the participation of this virtual state strongly enhances the electronic coupling required for charge/energy transfer. The unified picture of real versus virtual CT-mediated TET mechanisms paves the way for rationally designing the energetics at the inorganic semiconductor/organic molecule interface for high-efficiency TET important for many emerging applications. This work was supported by the Ministry of Science and Technology of China, CAS, the National Natural Science Foundation of China and the LiaoNing Revitalization Talents Program. The paper is dedicated to DICP, CAS, on the occasion of its 70th anniversary. (Text and Image by LUO Xiao).

Researchers under the direction of Profs. LI Xianfeng and ZHANG Huamin from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences recently developed an ultrathin ion-conducting membrane with high selectivity and conductivity that can boost the power of flow batteries. The study was published in Nature Communications. Membranes are key components of flow batteries. They separate reactive materials in the negative and positive chambers while permitting the transfer of ions across the membrane at the same time. The efficiency of flow batteries greatly depends on the ion selectivity and conductivity of these membranes. Based on their previous study (Energy. Environ. Sci., 2011, 4, 1676), LI's group found that the key challenge for ion-conducting membranes is the "trade-off" between ion selectivity and conductivity. Porous membranes using the traditional phase inversion method of construction had tortuous and poorly connected pores, resulting in low ion conductivity. In contrast, composite membranes possess separately tuned selective layers supported on substrates. "A composite membrane with a very thin selective layer and a highly conductive substrate hopefully overcomes the trade-off between ion selectivity and conductivity and further improves flow battery performance," said Prof. LI. To this end, the researchers utilized interfacial polymerization to fabricate a thin-film composite membrane. This membrane has an ultra-thin cross-linked polyamide selective layer and a highly conductive support layer. The ultrathin selective layer is only 180 nm thick. It offers a very short ion-transfer pathway and has very low area resistance. The cross-linked polyamide has free volume between the size of hydronium and hydrated vanadium ions. Vanadium ions, due to their size, are highly resistant to crossover, thus endowing the membrane with high ion selectivity.
　　The fabrication and function of the thin-film composite membrane. (Image by DAI Qing) Flow batteries with a thin-film composite membrane could work at higher current density. This would allow the use of a smaller battery stack to generate higher power and reduction in the cost of battery stacks. The proton transfer mechanism in polyamide selective layers can be further understood by utilizing the Grotthuss mechanism to make theoretical calculations of proton transfers along water chains and carboxyl groups. Results provide new ideas for designing advanced ion-selective membranes that can also be applied to flow batteries. (Text by DAI Qing)

Recently, Biomass Conversion Technology Group led by Prof. ZHAO Zongbao from Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) made a new progress in the research of non-natural cofactor. Researchers successfully constructed a non-natural cofactor and formate driven system with pathway-selective energy transfer. This work was published in Angewandte Chemie International Edition. Nicotinamide adenosine dinucleotide (NAD) and its reduced form are linked to hundreds of cellular reactions, and fluctuation of NAD(H) level causes global disturbance to cellular metabolism. To over come the limitations of the regulation of natural cofactors, the group led by Prof. ZHAO Zongbao has been working on the research area of non-natural cofactors. In previous works, bioorthogonal redox catalytic system was constructed with non-natural cofactor dependent oxidoreductase mutants via directed revolution (J. Am. Chem. Soc., 2011, 133, 20857). In addition, cofactor preference of phosphite dehydrogenase was engineered and the molecular basis of cofactor preference was elucidated (ACS Catal., 2019, 9, 1883). Moreover, researchers also constructed non-natural organic acids synthesis system driven by phosphite, selectively transferring energy to the metabolic pathways of bacteria (ACS Catal., 2017, 7, 1977). In this work, a nicotinamide cytosine dinucleotide (NCD) dependent formate dehydrogenase (FDH*) was obtained through directed evolution, and new bioorthogonal system was built with NCD dependent FDH* and malic enzyme (ME*). Results showed that pyruvate was reductive carboxylated with carbon unit and reducing power from formate. Further, researchers constructed a malate synthesis system driven by formate and NCD in microbe. This work reversed the natural direction of metabolic node of malate, showing great value for redesign of metabolic pathways and selectively regulation the substance and energy metabolism.
　　Non-natural cofactor and formate driven reductive carboxylation of pyruvate. FDH*: formate dehydrogenase mutant; ME*: malic enzyme mutant; NCD: nicotinamide cytosine dinucleotide. (Image by GUO Xiaojia) This work was supported by National Natural Science Foundation of China and Dalian Institute of Chemical Physics. (Text and image by GUO Xiaojia)