Multimodal Electrocorticogram Active Electrode Array Based on Zinc Oxide-Thin Film Transistors.

Active electrocorticogram (ECoG) electrodes can amplify weak electrophysiological signals and improve anti-interference ability; however, traditional active electrodes are opaque and cannot realize photoelectric collaborative observation. In this study, an active and fully transparent ECoG array based on zinc oxide thin-film transistors (ZnO TFTs) is developed as a local neural signal amplifier for electrophysiological monitoring. The transparency of the proposed ECoG array is up to 85%, which is superior to that of the previously reported active electrode arrays. Various electrical characterizations have demonstrated its ability to record electrophysiological signals with a higher signal-to-noise ratio of 19.9 dB compared to the Au grid (13.2 dB). The high transparency of the ZnO-TFT electrode array allows the concurrent collection of high-quality electrophysiological signals (32.2 dB) under direct optical stimulation of the optogenetic mice brain. The ECoG array can also work under 7-Tesla magnetic resonance imaging to record local brain signals without affecting brain tissue imaging. As the most transparent active ECoG array to date, it provides a powerful multimodal tool for brain observation, including recording brain activity under synchronized optical modulation and 7-Tesla magnetic resonance imaging.

Hierarchically Porous SnO2 Coupled Organic Carbon for CO2 Electroreduction.

Converting CO2 into value-added chemicals or fuels by electrochemical CO2 reduction reaction (CO2 RR) has aroused great interest, whereas designing highly active and selective electrocatalysts is still a challenge. Herein, a novel kind of electrochemical catalyst composed with SnO2 and organic carbon (OC), named as SnO2 /OC, was facilely constructed for CO2 RR. The obtained SnO2 /OC exhibits both high faradaic efficiency for formate (∼75 %) and carbon products (∼95 %) as well as excellent stability. High surface area with hierarchically porous structure and the homogeneous formation of Sn-O-C linkages in SnO2 /OC jointly promote the adsorption and activation of CO2 , as well as fast transport of reactants and products.

Engineering Active Fe Sites on Nickel-Iron Layered Double Hydroxide through Component Segregation for Oxygen Evolution Reaction.

Nickel-iron layered double hydroxide (NiFe LDH) is a promising oxygen evolution reaction (OER) electrocatalyst under alkaline conditions. Much research has been performed to understand the structure-activity relationship of NiFe LDH under OER conditions. However, the specific role of the Fe species remains unclear and under debate. Herein, based on DFT calculations, it was discovered that the edge Fe sites show higher activity towards OER than either the edge Ni sites or lattice sites. Therefore, a facile acid-etching method was proposed to controllably induce the formation of edge Fe sites in NiFe LDH, and the obtained sample exhibited higher OER activity. X-ray absorption near edge structure and extended X-ray absorption fine structure analyses further revealed that the interaction of the edge Fe species with Ni is believed to contribute to the enhancement of the OER performance. This work provides a new understanding of the structure-activity relationship in NiFe LDH and offers a facile method for the design of efficient electrocatalysts in an alkaline environment.

Pt/Fe co-loaded mesoporous zeolite beta for CO oxidation with high catalytic activity and water resistance.

A series of Pt/Fe co-loaded mesoporous zeolite beta (Pt/Fe-mBeta) catalysts with different Fe contents have been successfully synthesized by an ion exchange and subsequent ethylene glycol reduction method. The catalysts were characterized by XRD, N2 adsorption-desorption, TEM, SEM, XPS and H2-TPR. The optimized sample Pt/Fe(3)-mBeta shows high catalytic activity for CO oxidation under dry conditions, and the complete conversion temperature of CO is as low as 90 °C. More importantly, the sample Pt/Fe(3)-mBeta also shows excellent water resistance and good durability, which could meet the practical needs of exhaust purification of diesel vehicles. It is believed that the synergistic effect between varied-valence Pt/Fe species and the mesoporous zeolite support with high surface area and good water resistance jointly contribute to the excellent catalytic performance.

Key Single-Atom Electrocatalysis in Metal-Organic Framework (MOF)-Derived Bifunctional Catalysts.

Metal-organic framework (MOF)-derived materials have attracted increasing interest and show promising catalytic performances in many fields. Intensive efforts have been focused on the structure design and metal-site integration in MOF-derived catalysts. However, the key catalytic processes related with the metal sites in MOF-derived catalysts that dominate the electrocatalytic performance still remain obscure. Herein, we show a neglected but critical issue in the pyrolytic synthesis of MOF-derived catalysts: the coupled evolution of dual sites, that is, metallic sites and single-atom metal sites. The identification of active sites of single-atom sites from the visible particles has been elucidated through the combined X-ray spectroscopic, electron microscopic, and electrochemical studies. Interestingly, after a total removal of metallic cobalt sites, catalysts with purified single-atom metal sites show no faltering activity for either the oxygen reduction reaction (ORR) or hydrogen evolution reaction (HER), while significantly enhanced ORR selectivity is achieved; this reveals the dominant activity and selectivity contribution from single-atom electrocatalysis. The insight of the coupled evolution of dual sites and the as-demonstrated dual-site decoupling strategies open up a new routine for the design and synthesis of MOF-derived catalysts with the optimized single-atom electrocatalysis towards various electrochemical reactions.

Engineering Single-Atom Cobalt Catalysts toward Improved Electrocatalysis.

The development of cost-effective catalysts to replace noble metal is attracting increasing interests in many fields of catalysis and energy, and intensive efforts are focused on the integration of transition-metal sites in carbon as noble-metal-free candidates. Recently, the discovery of single-atom dispersed catalyst (SAC) provides a new frontier in heterogeneous catalysis. However, the electrocatalytic application of SAC is still subject to several theoretical and experimental limitations. Further advances depend on a better design of SAC through optimizing its interaction with adsorbates during catalysis. Here, distinctive from previous studies, favorable 3d electronic occupation and enhanced metal-adsorbates interactions in single-atom centers via the construction of nonplanar coordination is achieved, which is confirmed by advanced X-ray spectroscopic and electrochemical studies. The as-designed atomically dispersed cobalt sites within nonplanar coordination show significantly improved catalytic activity and selectivity toward the oxygen reduction reaction, approaching the benchmark Pt-based catalysts. More importantly, the illustration of the active sites in SAC indicates metal-natured catalytic sites and a media-dependent catalytic pathway. Achieving structural and electronic engineering on SAC that promotes its catalytic performances provides a paradigm to bridge the gap between single-atom catalysts design and electrocatalytic applications.

Anion-Regulated Selective Generation of Cobalt Sites in Carbon: Toward Superior Bifunctional Electrocatalysis.

The introduction of active transition metal sites (TMSs) in carbon enables the synthesis of noble-metal-free electrocatalysts for clean energy conversion applications; however, there are often multiple existing forms of TMSs, which are of different natures and catalytic models. Regulating the evolution of distinctive TMSs is highly desirable but remains challenging to date. Anions, as essential elements involved in the synthesis, have been totally neglected previously in the construction of TMSs. Herein, the effects of anions on the creation of different types of TMSs are investigated for the first time. It is found that the active cobalt-nitrogen sites tend to be selectively constructed on the surface of N-doped carbon by using chloride, while metallic cobalt nanoparticles encased in protective graphite layers are the dominant forms of cobalt species with nitrate ions. The obtained catalysts demonstrate cobalt-sites-dependent activity for oxygen reduction reaction and hydrogen evolution reaction in acidic media. The remarkably enhanced catalytic activities approaching that of benchmark Pt/C in an acidic medium have been obtained on the catalyst dominated with cobalt-nitrogen sites, confirmed by the advanced spectroscopic characterization. This finding demonstrates a general paradigm of anion-regulated evolution of distinctive TMSs, providing a new pathway for enhancing performances of various targeted reactions related with TMSs.

Nitrogen-Doped Carbon Vesicles with Dual Iron-Based Sites for Efficient Oxygen Reduction.

A nitrogen-doped vesicle-like porous carbon with well-integrated dual iron-based catalytic sites was developed through direct pyrolysis of inexpensive and abundant precursors. Benefiting from the mesoporous structures with synchronous construction of Fe-Nx and Fe/Fe3 C@NC sites, the optimized catalyst exhibited outstanding performance for the oxygen reduction reaction (ORR) in alkaline media, even superior to the commercial Pt/C catalyst. Detailed characterizations revealed that Fe/Fe3 C@NC sites can make major catalytic contributions in basic media, whereas the Fe-Nx sites were found to play an indispensable role for ORR in acidic media.

Genomic in situ hybridization analysis for identification of introgressed segments in alloplasmic lines from Zea mays x Zea diploperennis.

In this study, the tested four alloplasmic inbred lines, a2-4, a2-5, b1-1 and b2-1 were propagated from the same disease resistant individual in the parthenogenetic progenies of Zea mays L. cv. Lu 9 x Zea diploperennis (DP). All the lines except a2-5 were resistant to Helminthosporium turcium Pass and H. maydis Nisik. Introgressed DP segments in these lines were detected by both Southern hybridization and genomic in situ hybridization (GISH). The results of Southern hybridization showed that DP species-specific DNA sequences had been introgressed into the genomes of alloplasmic lines. The Southern hybridization band patterns in all of the tested lines were consistent with those of DP. Genomic in situ hybridization (GISH) signals were detected on 7 different chromosome pairs in lines a2-4 and a2-5, on 5 chromosome pairs in b1-1 and on 4 chromosome pairs in b2-1. The features of introgression, and disease resistant genes in the introgressed segments, as well as the gene silence or elimination in some alloplasmic lines are discussed.