Ammonia is essential for food and future energy supply. In the industry, it is mainly produced by the Haber-Bosch process, which operates at high temperatures and pressures.
　　Due to the ammonia industry's high energy consumption and carbon emissions, it is important to develop alternative materials and approaches for efficient N2 reduction to ammonia driven by renewable energy.
　　Recently, a research group led by Prof. CHEN Ping from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has realized photo-driven nitrogen fixation and ammonia synthesis mediated by lithium hydride (LiH).
　　This study was published in Nature Chemistry on Jan. 16.
　　LiH is the simplest saline hydride with a band gap of 3.7 eV. It has been investigated for hydrogen storage due to its high hydrogen content (12.5 wt%). However, the dehydrogenation of LiH is thermodynamically unfavorable.
　　In this study, the researchers found that ultraviolet (UV) illumination of LiH could induce a notable color change from white to light blue, accompanied by the release of a small amount of H2 under ambient conditions. Such a phenomenon implied that under UV illumination, LiH underwent photolysis resulting in photon-generated electrons trapped in its hydrogen vacancy as long-lived and electron-rich F centers, which showed a fundamentally different mechanism for charge carrier separation.
　　Schematics for the photo-driven nitrogen fixation process of LiH and the photocatalytic ammonia synthesis performance (Image by GUAN Yeqin)
　　The researchers indicated that illuminated LiH had an electron-rich surface with hydrogen vacancies, which facilitated the activation of N2 to form N-H bond. Moreover, the researchers co-fed a N2/H2 mixture with a low H2 partial pressure into the LiH powders, leading to photo-catalytic ammonia production under ambient conditions.
　　"This photochemical route is flexibility in operation, which may be amenable to the small-scale and distributed ammonia synthesis powered by intermittent solar energy," said Prof. CHEN.
　　This work was supported by the Ministry of Science and Technology of China, the National Natural Science Foundation of China, and the Youth Innovation Promotion Association of CAS.

　　Recently, a team led by Prof. WU Zhong-Shuai has developed novel 2D atomically thin (001)-oriented single-crystalline LiCoO2 nanosheets with longer Li+ intercalation distance and (001) planes dominated surface for high-performance battery-supercapacitor hybrid devices.
　　This study was published in ACS Energy Letters on Jan 5.
　　Shorter Li+ intercalation distance or lower intercalation energy barrier enables fast diffusion in Li+ intercalation process. However, it is found that nanosize effect in nanocrystalline LiCoO2 affects surface-redox and Li+ intercalation processes simultaneously.
　　As the crystallite size decreases, more Li+ intercalation processes are replaced by surface-redox processes, which brings about decreased platform capacity, low initial coulombic efficiency, and poor cycle performance. Therefore, the nanosize effect restricted the application of nanostructured LiCoO2 in "double high" battery-supercapacitor hybrid devices.
　　To solve the above problem, Prof. WU's team attempted to regulate the nanosize effect by precisely controlling the Li+ intercalation process and surface-redox process.
　　They synthesized micro-sized atomically thin single-crystalline LCO nanosheets (SC-LCO) and nanocrystalline LCO nanosheets (NC-LCO). Compared with NC-LCO, SC-LCO presented longer Li+ intercalation distance and decreased side reactions.
　　They have found that both coulombic efficiency and discharge capacity of SC-LCO at 1C (194 mAh g-1, 92%) were higher than NC-LCO (173 mAh g-1, 86%). The specific capacity of SC-LCO maintained 151 mAh g-1 (83%) after cycling for 500 cycles, which preceded NC-LCO (84 mAh g-1, 63%).
　　Moreover, the researchers fabricated a battery-supercapacitor hybrid device with SC-LCO and achieved high-energy and high-power, demonstrating the practical applicability of this nanosheets.
　　The above study was supported by the National Natural Sciences Foundation of China, the DICP Innovation Foundation.

　　Overall water splitting (OWS) using suspended particulate photocatalysts to produce green hydrogen is promising due to its cost-effective and easy large-scale application.
　　However, due to lack of inefficient cocatalysts and poor interface of cocatalyst and semiconductor, the challenging charge separation restricts the improvement of apparent quantum efficiency (AQE) under visible light.
　　Recently, a research group led by Prof. ZHANG Fuxiang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) revealed that the strong metal-support interaction (SMSI) could promote the interfacial charge separation and water oxidation activity of Ir/BiVO4 photocatalyst system, based on which they fabricated a highly-efficient redox-driven Z-scheme OWS system with a AQE of 16.9% at 420 ±10 nm under room temperature.
　　This study was published in Joule on Jan. 02.
　　The researchers obtained the Ir/BiVO4 photocatalyst with SMSI effect by high temperature hydrogen reduction treatment, and they verified that the SMSI could promote interfacial charge separation. In addition, by in-situ photoinduction, Ir species were converted into Ir and IrO2 dual-cocatalysts on the {010} and {110} facets of BiVO4, which further improved its surface catalysis and charge separation, leading the increased water oxidation performance of BiVO4 by more than 75 times.
　　On this basis, they constructed a photocatalytic Z-scheme OWS system with benchmarking AQE value of artificial photosynthesis using suspended powder photocatalyst, together with the TaON-based photocatalyst as H2-evolving photocatalyst and [Fe(CN)6]3-/4- as redox ion.
　　"This study not only extends the application of SMSI from the traditional thermal catalysis to the field of photocatalysis, but also provides a new idea for promoting photogenerated charge separation," said Prof. ZHANG.
　　This work was supported by the National Natural Science Foundation of China and the National Key R&D Program of China.

　　Recently, a research team led by Prof. LI Xianfeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) developed a 70 kW-level high power density vanadium flow battery stack. Compared with the current 30kW-level stack, this stack has a volume power density of 130kW/m3, and the cost is reduced by 40%.
　　70 kW-level vanadium flow battery stack and its charge/discharge profile (Image by XING Feng)
　　Vanadium flow batteries are one of the preferred technologies for large-scale energy storage. At present, the initial investment of vanadium flow batteries is relatively high.
　　Stack is the core component of a vanadium flow battery. The power density determines the cost of the stack. The higher the power density is, the smaller the stack volume is, resulting in lower cost under the same power output conditions.
　　Based on self-developed highly selective weldable porous composite membranes and weldable highly conductive bipolar plates, Prof. LI's team developed a 70kW-level stack, using a short flow path, an ultra-thin battery structure, and low flow resistance and high distribution uniformity flow channels.
　　The energy efficiency of this stack is 81.0% under 70kW rated power charge and discharge conditions, and the energy efficiency is 82.1% under 60kW constant power charge and discharge conditions. In addition, the stack operates stably after more than 1,200 cycles, with only 1.7% energy efficiency decay.
　　By using this stack, a 20-foot container energy storage unit module can be upgraded from 250kW to 500kW without greatly increasing the size of power units and the cost of system-supporting facilities.
　　"This 70kW-level stack can promote the commercialization of vanadium flow batteries. We believe that the development of this stack will improve the integration of power units in energy," said Prof. LI.

　　The flavonoid xanthohumol, which is an important flavor substance in the brewing industry, has a wide variety of bioactivities.
　　However, its unstable structure is easily oxidized during the brewing process, resulting in its low content in beer. Moreover, its extraction and purification from plants requires laborious and expensive procedures, and hops cultivation is susceptible to environmental factors.
　　Recently, a research group led by Prof. ZHOU Yongjin from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has proposed a microbial platform for the de novo biosynthesis of xanthohumol from glucose.
　　It can synthesize flavonoids, such as the key xanthohumol precursor demethylxanthohumol (DMX) and xanthohumol, owing to balancing the three parallel biosynthetic pathways and enhancing the prenylation efficiency by rewiring the cellular metabolism of Saccharomyces cerevisiae.
　　This study was published in Nature Communications on Jan. 4.
　　Engineering the yeast Saccharomyces cerevisiae for biosynthesis of xanthohumol by optimizing the biosynthetic pathway and rewiring the cellular metabolism (Image by ZHOU Yongjin)
　　The researchers systematically engineered the budding yeast Saccharomyces cerevisiae for an 83-fold improvement in the demethylxanthohumol (DMX) production (4 mg/L) by balancing the three parallel biosynthetic pathways, prenyltransferase engineering, enhancing precursor supply, enzyme fusion, and peroxisomal engineering.
　　Furthermore, they expressed the last methylation step produced 142 μg/L xanthohumol in shake flasks from glucose.
　　"Our work constructed a microbial cell factory for biosynthesis of xanthohumol and provided feasible approaches to optimize other complex biosynthetic pathways of natural products," said Prof. ZHOU.

　　Ethylene methoxycarbonylation reaction is the key process in the Alpha-route to produce methyl methacrylate industrially. This approach has the advantages of using widely available raw materials, having high atomic efficiency, as well as high selectivity when compared with traditional methodologies such as acetone-cyanohydrins, isobutene oxidation and ethylene hydroformylation.
　　However, ethylene methoxycarbonylation reaction still employs homogeneous Pd-P complexes as catalysts, and uses strongly corrosive acids as promoters, which has difficulty in the recovery of the catalysts and raise environmental concerns.
　　Recently, a research group led by Profs. ZHANG Tao and WANG Aiqin from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) realized the ethylene methoxycarbonylation reaction over Pt1/MoS2 single-atom catalyst (SAC).
　　Pocket-like ensemble of Mo-S-Pt1-S-Mo sites for ethylene methoxycarbonylation by M-H mechanism (Image by WANG An)
　　As a bridge between homogeneous and heterogeneous catalysis, SACs are regarded as new opportunities. In this study, the researchers fabricated MoS2 nanosheets supported Pt SAC, where Pt formed multi-functional Mo-S-Pt-S-Mo entities with Mo atoms on the support.
　　They found that the metal-support concerted catalysis, Pt1/MoS2 presented good catalytic performances in ethylene methoxycarbonylation reaction under acid promoter-free conditions. The turnover frequency (TOF) reached 320 h-1, comparable to some homogeneous catalysts. Pt1/MoS2 could be reused without significant decay in catalytic activity.
　　"Our study provides a new way to design and develope efficient heterogeneous catalysts for alkoxycarbonylation reactions of alkenes," said Prof. WANG.
　　The above work was supported by the National Natural Science Foundation of China, the CAS Project for Young Scientists in Basic Research, and the National Key Projects for Fundamental Research and Development of China.