Electrothermal Water-Gas Shift Reaction at Room Temperature with a Silicomolybdate-Based Palladium Single-Atom Catalyst.

The water-gas shift (WGS) reaction is often conducted at elevated temperature and requires energy-intensive separation of hydrogen (H2 ) from methane (CH4 ), carbon dioxide (CO2 ), and residual carbon monoxide (CO). Designing processes to decouple CO oxidation and H2 production provides an alternative strategy to obtain high-purity H2 streams. We report an electrothermal WGS process combining thermal oxidation of CO on a silicomolybdic acid (SMA)-supported Pd single-atom catalyst (Pd1 /CsSMA) and electrocatalytic H2 evolution. The two half-reactions are coupled through phosphomolybdic acid (PMA) as a redox mediator at a moderate anodic potential of 0.6 V (versus Ag/AgCl). Under optimized conditions, our catalyst exhibited a TOF of 1.2 s-1 with turnover numbers above 40 000 mol CO 2 ${{_{{\rm CO}{_{2}}}}}$ molPd -1 achieving stable H2 production with a purity consistently exceeding 99.99 %.

QCW surface-pumped cryogenically cooled single-slab laser with 1 kW level at 946 nm.

We present a kilowatt-level quasi-continuous-wave (QCW) cryogenically cooled 946-nm slab laser oscillator for the first time, to the best of our knowledge. The laser system is based on a double-face-pumped large-size single-slab Nd:YAG design, delivering a record-high average power of 1.06 kW without additional amplification. This laser oscillator operates at repetition rate of 400 Hz with a pulse duration of 175 µs, resulting in a single pulse energy of 2.65 J. To the best of our knowledge, these results represent the highest output power and pulse energy for any all-solid-state 946-nm laser ever reported to date. Our scheme paves a new path for the development of the compact high-power solid-state 946-nm laser.

1.53 W all-solid-state nanosecond pulsed mid-infrared laser at 6.45 µm.

A compact and robust all-solid-state mid-infrared (MIR) laser at 6.45 µm with high average output power and near-Gaussian beam quality is demonstrated. A maximum output power of 1.53 W with a pulse width of approximately 42 ns at 10 kHz is achieved using a ZnGeP2 (ZGP) optical parametric oscillator (OPO). This is the highest average power at 6.45 µm of any all-solid-state laser to the best of our knowledge. The average beam quality factor is measured to be M2 = 1.19. Moreover, high output power stability is confirmed, with a power fluctuation of less than 1.35% rms over 2 h, and the laser can run efficiently for more than 500 h in total. Using this 6.45 µm pulse as a radiation source, ablation of animal brain tissue is tested. Furthermore, the collateral damage effect is theoretically analyzed for the first time, to the best of our knowledge, and the results indicate that this MIR laser has excellent ablation ability, making it a potential replacement for free electron lasers.

A general strategy for semiconductor quantum dot production.

Mass production of semiconductor quantum dots (QDs) from bulk materials is highly desired but far from being satisfactory. Herein, we report a general strategy to mechanically tailor semiconductor bulk materials into QDs. Semiconductor bulk materials are routinely available via simple chemical precipitation. From their bulk materials, a variety of semiconductor (e.g., lead sulfide (PbS), cadmium sulfide (CdS), copper sulfide (CuS), ferrous sulfide (FeS), and zinc sulfide (ZnS)) QDs are successfully produced in high yields (>15 wt%). This is achieved by a combination of silica-assisted ball-milling and sonication-assisted solvent treatment. The as-produced QDs show intrinsic characteristics and outstanding water solubility (up to 5 mg mL-1), facilitating their practical applications. The QD dispersions present remarkable photoluminescence (PL) with exciton-dependence and nanosecond (ns)-scale lifetimes. The QDs-poly(methyl methacrylate) (PMMA) hybrid thin films demonstrate exciting solid-state fluorescence and exceptional nonlinear saturation absorption (NSA). Absolute modulation depths of up to 58% and saturation intensities down to 0.40 MW cm-2 were obtained. Our strategy could be applied to any semiconductor bulk materials and therefore paves the way for the construction of the complete library of semiconductor QDs.

Enhanced Oxygen Reduction Catalysis of Carbon Nanohybrids from Nitrogen-Rich Edges.

The edge doping effect would help improve the carbon-based electrocatalysis. Herein, we present an all-mechanical technique for the fabrication of cut, exfoliated N-doped carbon nanotubes (C, E-N-CNTs). Such nanohybrids with an edge-N-rich structure are obtained through sequential doping and mechanical treatments of the pristine bulk-CNTs. The C, E-N-CNT/carbon black (C, E-N-CNT/C) demonstrates exciting oxygen reduction reaction (ORR) electrocatalysis with exceptionally low-onset potential (E0, 913 mV versus RHE) and satisfactory half-wave potential (E1/2, merely -7.3 mV shift compared with that of commercial 20% platinum/C (Pt/C)). Besides, the C, E-N-CNT/C presents significantly enhanced durability and tolerance in chronoamperometry test with methanol injection compared with the Pt/C. Our work would facilitate the mass production and full exploration of nonmetallic electrocatalysts.

Tailoring Multi-Walled Carbon Nanotubes into Graphene Quantum Sheets.

Transformation of carbon nanotubes (CNTs) into sub-10 nm pieces is highly required but remains a great challenge. Herein, we report a robust strategy capable of mechanically tailoring pristine multi-walled carbon nanotubes (MWCNTs) into graphene quantum sheets (M-GQSs) with an extremely high yield of up to 44.6 wt %. The method combines silica-assisted ball-milling and sonication-assisted solvent exfoliation and therefore enables reproducible high-yield production of M-GQSs directly from MWCNTs. Remarkable solvent diversity and extraordinary solvability (up to 7 mg/mL) are demonstrated facilitating the solution processing of the M-GQSs. The M-GQSs are essentially monolayers with intrinsic curvature, which could be determinative to their outstanding performances in both dispersions and thin films. Besides the excitation wavelength-, concentration-, and solvent-dependent photoluminescence in dispersions, the solid-state fluorescence and exceptional nonlinear saturation absorption (NSA) in thin films are demonstrated. Particularly, NSA with relative modulation depth up to 46% and saturation intensity down to 1.53 MW/cm2 are achieved in M-GQS/poly(methyl methacrylate) hybrid thin films with a loading content of merely 0.2 wt %. Our method opens up a new avenue toward conversion and utilization of CNTs.

Cobalt/nitrogen codoped carbon nanosheets derived from catkins as a high performance non-noble metal electrocatalyst for oxygen reduction reaction and hydrogen evolution reaction.

Novel energy devices which are capable of alleviating and/or solving the energy dilemma such as overall water splitting and fuel cells require the development of highly efficient catalysts, especially cheap high performance non-precious metal (NPM) catalysts. Here, we prepare highly efficient NPM catalysts of cobalt and nitrogen codoped carbon nanosheets (Co/N-CNSs) for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) using harmful environment-polluting waste of biomass catkins as carbon precursors via a mild mechanical exfoliation and chemical process which is facile, low-cost, environmentally friendly and up-scalable. Compared with a commercial platinum-based catalyst (commercial 20% Pt/C), the Co/N-CNS electrocatalysts show outstanding ORR activity, acceptable HER activity and long term stability with an onset potential of 0.92 V versus the reversible hydrogen electrode (vs. RHE) and a half-wave potential of 0.83 V vs. the RHE in alkaline electrolytes. The excellent performance is closely related to the presence of abundant CoN x active sites. This work offers a novel and effective approach for preparing highly efficient ORR and HER NPM electrocatalysts from waste biomass materials.

High-Yield Production of MoS2 and WS2 Quantum Sheets from Their Bulk Materials.

Mass production of two-dimensional quantum sheets (2D QSs) is highly desired to fully exploit their properties. Herein, we present a general strategy for the high-yield production of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) QSs by a sequential combination of salt-assisted ball-milling and sonication-assisted solvent exfoliation of their bulk materials. Such a strategy enables reproducible production of intrinsic and defect-free MoS2 and WS2 QSs with exceedingly high yields of 25.5 and 20.1 wt %, respectively. By precipitation-redispersion treatment, the QSs can be redispersed in a wide range of solvents with redispersion concentration up to 20 mg/mL or even higher. Remarkable nonlinear absorption saturation is demonstrated in the QSs-poly(methyl methacrylate) (PMMA) hybrid thin film with loading content of merely 0.1 wt %. Our method provides an avenue toward mass production and full exploration of 2D QSs.