Enhancement of Catalytic Activity via Inevitable Reconstruction of the Ni-Mo Interface for Alkaline Hydrogen Oxidation.

The inevitable oxidation of nickel-metal-based catalysts exposed to the air will lead to instability and poor reproducibility of a catalytic interface, which is usually ignored and greatly hinders their application for the catalysis of alkaline hydrogen oxidation. The details on the formation of a world-class nickel-based HOR catalyst Ni3-MoOx/C-500 are reported via an interfacial reconstruction triggered by passive oxidation upon air exposure. Interfacial reconstruction, initiated with various Ni-Mo metal ratios and annealing temperature, can fine-tune the Ni-Mo interface with an increased work function and a reduced d-band center. The optimized Ni3-MoOx/C exhibits a record high mass activity of 102.8 mA mgNi -1, a top-level exchange current density of 76.5 µA cmNi -2, and exceptional resistance to CO poisoning at 1000 ppm CO for hours. The catalyzed alkaline exchange membrane fuel cell exhibits a maximum power output of 600 mW cm-2 and excellent stability, ranking it as one of the most active non-precious metals HOR catalysts to date.

Magnetic Moment Preservation and Emergent Kondo Resonance of Co-Phthalocyanine on Semimetallic Sb(111).

Magnetic molecules on surfaces have been widely investigated to reveal delicate interfacial couplings and for potential technological applications. In these endeavors, one prevailing challenge is how to preserve or recover the molecular spins, especially on highly metallic substrates that can readily quench the magnetic moments of the admolecules. Here, we use scanning tunneling microscopy and spectroscopy to exploit the semimetallic nature of antimony and observe, surprisingly yet pleasantly, that the spin of Co-phthalocyanine is well preserved on Sb(111), as unambiguously evidenced by the emergent strong Kondo resonance across the molecule. Our first-principles calculations further confirm that the optimal density of states near the Fermi level of the semimetal is a decisive factor, weakening the overall interfacial coupling, while still ensuring sufficiently effective electron-spin scattering in the many-body system. Beyond isolated admolecules, we discover that each of the magnetic moments in a molecular dimer or a densely packed island is distinctly preserved as well, rendering such molecular magnets immense potentials for ultrahigh density memory devices.

Compartmentalizing Incompatible Tandem Reactions in Pickering Emulsions To Enable Visual Colorimetric Detection of Nitramine Explosives Using a Smartphone.

We report a visual colorimetric assay for detection of nitramine explosives such as 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) using a smartphone. This assay is based on compartmentalizing incompatible tandem reactions in Pickering emulsions. The alkaline hydrolysis of RDX or HMX in one Pickering emulsion produces nitrite ions, which autodiffuse into the other Pickering emulsion to form nitrous acid. It oxidizes the 3,3',5,5'-tetramethylbenzidine (TMB) to generate yellow TMB diimine. The RGB component change of the optical images is applied to quantitatively determine the RDX and HMX at different reaction temperatures. A distinct color change occurs at RDX and HMX concentrations of 1.2 and 12 µM, respectively. The adjusted intensity increases linearly with the increase of the logarithms of the concentrations of RDX and HMX in the range of 1.2-90 µM and 12-90 µM, respectively. The limits of detection of RDX and HMX are 96 and 110 nM, respectively. Importantly, this assay is employed for the detection of RDX and HMX in real water, proving the applicability of the assay in real-world samples.

Temperature-Induced Interface Hybridization of WC Boosts NiCu Activity for Alkaline Hydrogen Oxidation Reaction.

The development of non-precious hydrogen oxidation reaction (HOR) catalysts is a major challenge for the commercialization of Pt-free fuel cells. Herein, a temperature-induced phase hybridization method is reported that greatly improves the catalytic performance of NiCu alloy for the HOR. The migration of W atoms hybridizes the interface of tungsten oxide (WOx) and tungsten carbide (WC) at the onset reduction temperature of WOx, leading to a greatly weakened H binding energy and an optimized OH binding energy, which endows NiCuW/WOx-WC@WC with favorable stability and CO resistance during HOR. The hybridization catalysts deliver a high mass activity of 29.37 mA mg-1 Ni and reach a peak power of 298 mW.cm-2 in H2-O2 anion exchange membrane fuel cells (AEMFCs).

Constructing CO-immune water dissociation sites around Pt to achieve stable operation in high CO concentration environment.

The serious problem of carbon monoxide (CO) poisoning on the surface of Pt-based catalysts has long constrained the commercialization of proton exchange membrane fuel cells (PEMFCs). Regeneration of Pt sites by maintaining CO scavenging ability through precise construction of the surface and interface structure of the catalyst is the key to obtaining high-performance CO-resistant catalysts. Here, we used molybdenum carbide (MoCx) as the support for Pt and introduced Ru single atoms (SA-Ru) at the Pt-MoCx interface to jointly decrease the CO adsorption strength on Pt. More importantly, the MoCx and SA-Ru are immune to CO poisoning, which continuously assists in the oxidation of adsorbed CO by generating oxygen species from water dissociation. These two effects combine to confer this anode catalyst (SA-Ru@Pt/MoCx) remarkable CO tolerance and the ability to operate stably in fuel cell with high CO concentration (power output 85.5 mW cm-2@20,000 ppm CO + H2 - O2), making it possible to directly use the cheap reformed hydrogen as the fuel for PEMFCs.

A phosphate tolerant Pt-based oxygen reduction catalyst enabled by synergistic modulation of alloying and surface modification.

Addressing phosphoric acid poisoning of platinum-based catalysts in high-temperature fuel cells still remains a strategic and synthetic problem. Here, we synthesized a Pt3Co@MoOx-NC catalyst with a Pt3Co active core and MoOx modification on the surface, which simultaneously exhibits high ORR activity and phosphate tolerance.

Amorphous SnSx (1 < x < 2) Anode with a High-Rate Li Alloying Reaction for Li-Ion Batteries.

Here, we report the conversion of bulk Li alloying anode reactions into surface reactions by the construction of amorphous structured SnSx active materials encapsulated in robust carbon nanofiber anodes. The high-temperature phase transformation from SnS to SnS2 is used to construct the SnSx (1 < x < 2) active material with an amorphous structure and ultra-tiny particle size, leading to a decreased Li+ diffusion path, weakened volume change ratio, but considerably enhanced capacitance. The amorphous structure changes the Li-storage mechanism from Li-intercalation to the surface reaction, which endows each active particle with a rapid (de)lithiation characteristic. As a result, the high-rate (dis)charge property with a long-term cycle life is obtained for SnSx@NC, which delivers an excellent rate capability of 633.4 mAh g-1 under 7 A g-1 and a capability retention of 785.2 mAh g-1 after 1600 cycles under 2 A g-1.

Overexpression of ßCaMKII impairs behavioral flexibility and NMDAR-dependent long-term depression in the dentate gyrus.

Behavioral flexibility is in close proximity to dentate gyrus (DG) function and long-term depression (LTD), but the role of DG LTD in behavioral flexibility has hitherto been unexplored. Although the functions of alpha-Ca2+/calmodulin-dependent protein kinase II (CaMKII) have been studied extensively, the role of ßCaMKII, a constituent of the CaMKII holoenzyme, in LTD and behavioral flexibility has not been investigated in vivo. Here using the ßCaMKII-F90G transgenic (TG) mice, in which the inducible and reversible overexpression of ßCaMKII is restricted to dentate gyrus (DG), we found that TG mice exhibited defective behavioral flexibility in two reversal tasks and seriously impaired N-methyl-d-aspartic acid receptor (NMDAR)-dependent LTD in DG medial perforant path (MPP). Consistent with the deficit in NMDAR-LTD, GluA1-Ser845, GluA1-Ser831 dephosphorylation and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) internalization were also disrupted during NMDAR-LTD in TG mice. Furthermore, these deficits were due to decreased activities of protein phosphatases (PP) 1/2A and glycogen synthesis kinase 3 beta (GSK3ß), and overexpressed synaptic stargazin in TG mice. Importantly, all the deficits above could be reversed by 1-naphthylmethyl (NM)-PP1, a specific inhibitor of the exogenous ßCaMKII-F90G. Taken together, our findings for the first time demonstrate that ßCaMKII overexpression impairs behavioral flexibility and NMDAR-dependent LTD in DG MPP, which further confirms the close relationship between NMDAR-dependent LTD and behavioral flexibility.