Intermetallic Ni3Ga1 Catalyst for Efficient Ammonia Reforming of Light Alkane.

Ammonia reforming of light alkane is conventionally employed for HCN production where coproduct H2 is burned for heating owing to the high reaction temperature (1200 °C) of such a highly endothermic process. Here, we show that a Ni3Ga1 intermetallic compound (IMC) catalyst is highly efficient for such a reaction, realizing efficient conversion of C1-C3 alkanes at 575-750 °C. This makes it feasible for on-purpose COx-free H2 production assuming that ammonia, as an H2 carrier, is ubiquitously available from renewable energy. At 650 °C and an alkane/ammonia ratio of 1/2, ethane and propane conversion of ∼20% and methane conversion of 13% were obtained (with nearly 100% HCN selectivity for methane and ethane) over the unsupported Ni3Ga1 IMC, which also shows high stability due to the absence of coke deposition. This breakthrough is achieved by employing a stoichiometric Ni3Ga1 mixed oxalate solid solution as the precursor for the Ni3Ga1 IMC.

Tailoring the d-band center on Ru1Cu single-atom alloy nanotubes for boosting electrochemical non-enzymatic glucose sensing.

The development of cost-effective and highly efficient electrocatalysts is critical to help electrochemical non-enzymatic sensors achieve high performance. Here, a new class of catalyst, Ru single atoms confined on Cu nanotubes as a single-atom alloy (Ru1Cu NTs), with a unique electronic structure and property, was developed to construct a novel electrochemical non-enzymatic glucose sensor for the first time. The Ru1Cu NTs with a diameter of about 24.0 nm showed a much lower oxidation potential (0.38 V) and 9.0-fold higher response (66.5 µA) current than Cu nanowires (Cu NWs, oxidation potential 0.47 V and current 7.4 µA) for glucose electrocatalysis. Moreover, as an electrochemical non-enzymatic glucose sensor, Ru1Cu NTs not only exhibited twofold higher sensitivity (54.9 µA mM-1 cm-2) and wider linear range (0.5-8 mM) than Cu NWs, but also showed a low detection limit (5.0 µM), excellent selectivity, and great stability. According to theoretical calculation results, the outstanding catalytic and sensing performance of Ru1Cu NTs could be ascribed to the upshift of the d-band center that helped promote glucose adsorption. This work presents a new avenue for developing highly active catalysts for electrochemical non-enzymatic sensors.

Breaking the Size Limitation of Directly-Synthesized PbS Quantum Dot Inks Toward Efficient Short-wavelength Infrared Optoelectronic Applications.

PbS quantum dots (QDs) are promising building blocks for solution-processed short-wavelength infrared (SWIR) devices. The recently developed direct synthesis of semi-conductive PbS QD inks has substantially simplified the preparation processing and reduced the material cost, while facing the challenge to synthesize large-size QDs with absorption covering the SWIR region. Herein, we for the first time realize a low-cost, scalable synthesis of SWIR PbS QD inks after an extensive investigation of the reaction kinetics. Finally, based on these PbS SWIR QD inks, the solar cell demonstrates a record-high power conversion efficiency (PCE) of 1.44 % through an 1100 nm cutoff silicon filter and the photodetector device shows a low dark current density of 2×10-6  A cm-2 at -0.8 V reverse bias with a high external quantum efficiency (EQE) of 70 % at ≈1300 nm. Our results realize the direct synthesis of low-cost and scalable SWIR QD inks and may accelerate the industrialization of consumer SWIR technologies.

A Carboranyl Electrolyte Enabling Highly Reversible Sodium Metal Anodes via a "Fluorine-Free" SEI.

Realization of practical sodium metal batteries (SMBs) is hindered due to lack of compatible electrolyte components, dendrite propagation, and poor understanding of anodic interphasial chemistries. Chemically robust liquid electrolytes that facilitate both favorable sodium metal deposition and a stable solid-electrolyte interphase (SEI) are ideal to enable sodium metal and anode-free cells. Herein we present advanced characterization of a novel fluorine-free electrolyte utilizing the [HCB11 H11 ]1- anion. Symmetrical Na cells operated with this electrolyte exhibit a remarkably low overpotential of 0.032 V at a current density of 2.0 mA cm-2 and a high coulombic efficiency of 99.5 % in half-cell configurations. Surface characterization of electrodes post-operation reveals the absence of dendritic sodium nucleation and a surprisingly stable fluorine-free SEI. Furthermore, weak ion-pairing is identified as key towards the successful development of fluorine-free sodium electrolytes.

Solvation Structure of Methanol-in-Salt Electrolyte Revealed by Small-Angle X-ray Scattering and Simulations.

The solvation structure of water-in-salt electrolytes was thoroughly studied, and two competing structures─anion solvated structure and anion network─were well-defined in recent publications. To further reveal the solvation structure in those highly concentrated electrolytes, particularly the influence of solvent, methanol was chosen as the solvent for this proposed study. In this work, small-angle X-ray scattering, small-angle neutron scattering, Fourier-transform infrared spectroscopy, and Raman spectroscopy were utilized to obtain the global and local structural information. With the concentration increment, the anion network formed by TFSI- became the dominant structure. Meanwhile, the hydrogen bonds among methanol were interrupted by the TFSI- anion and formed a new connection with them. Molecular dynamic simulations with two different force fields (GAFF and OPLS-AA) are tested, and GAFF agreed with synchrotron small-angle X-ray scattering/wide-angle X-ray scattering (SAXS/WAXS) results well and provided insightful information about molecular/ion scale solvation structure. This article not only deepens the understanding of the solvation structure in highly concentrated solutions, but more importantly, it provides additional strong evidence for utilizing SAXS/WAXS to validate molecular dynamics simulations.

Turning dead leaves into an active multifunctional material as evaporator, photocatalyst, and bioplastic.

Large numbers of leaves fall on the earth each autumn. The current treatments of dead leaves mainly involve completely destroying the biocomponents, which causes considerable energy consumption and environmental issues. It remains a challenge to convert waste leaves into useful materials without breaking down their biocomponents. Here, we turn red maple dead leaves into an active three-component multifunctional material by exploiting the role of whewellite biomineral for binding lignin and cellulose. Owing to its intense optical absorption spanning the full solar spectrum and the heterogeneous architecture for effective charge separation, films of this material show high performance in solar water evaporation, photocatalytic hydrogen production, and photocatalytic degradation of antibiotics. Furthermore, it also acts as a bioplastic with high mechanical strength, high-temperature tolerance, and biodegradable features. These findings pave the way for the efficient utilization of waste biomass and innovations of advanced materials.

Molecular-Weight-Dependent Infiltration and Adsorption of Polymers into Nanochannels.

The mesoporous silica shell coating hydrogenolysis nano-catalysts alters the molecular weight distributions of cleaved polymer chains compared to catalysts without a shell. The shell, composed of radially aligned narrow cylindrical nanopores, reduces the formation of low-valued gaseous products and increases the median molecular weight of the product, thus enhancing the value of the products for polymer upcycling. To understand the role of the mesoporous shell, we have studied the spatial distribution of polystyrene chains, used as a model polymer, in the nanochannels in both the melt phase and solution phase. In the melt, we observed from small-angle X-ray scattering experiments that the infiltration rate of the polymer into the nanochannels is inversely proportional to the molecular weight, which is consistent with theory. In theta solution experiments using UV-vis spectroscopy, we found that the shell significantly enhances polymer adsorption compared to nanoparticles without pores. In addition, the degree of polymer adsorption is not a monotonic function of molecular weight but initially increases with the molecular weight before eventually decreasing. The molecular weight for the peak adsorption increases with the pore diameter. This adsorption behavior is rationalized as resulting from a balance between the mixing entropy gain by surface adsorption and the conformational entropy penalty incurred by chains confined in the nanochannels. The spatial distribution of polymer chains in the nanochannels is visualized by energy-dispersive X-ray spectroscopy (EDX), and inverse Abel-transformed data reveals a less uniform polymer distribution along the primary pore axis for longer chains.

Operando X-ray Absorption Spectroscopy Study of SnO2 Nanoparticles for Electrochemical Reduction of CO2 to Formate.

Tin-based electrocatalysts exhibit a remarkable ability to catalyze CO2 to formate selectively. Understanding the size-property relationships and exploring the evolution of the active size still lack complete understanding. Herein, we prepared SnO2 nanoparticles (NPs) with a controllable size supported on commercial carbon spheres (SnO2/C-n, n = 1, 2, and 3) by a simple low-temperature annealing method. The transmission electron microscopy/scanning transmission electron microscopy images and fitting results of the small-angle X-ray scattering profile confirm the increased size of SnO2 NPs due to the increase of SnO2 loading. The catalytic performance of SnO2 has proved the size-dependent effect during the CO2 reduction reaction process. The as-prepared SnO2/C-1 displayed the maximum Faradic efficiency of formate (FEHCOO-) of 82.7% at -1.0 V versus reversible hydrogen electrode (RHE). In contrast, SnO2/C-2 and SnO2/C-3 with larger particle sizes achieved lower maximum FEHCOO- and larger overpotential. Moreover, we employed operando X-ray absorption spectroscopy to study the evolution of the oxidation state and local coordination environment of SnO2 under working conditions. In addition to the observed shifts of the rising edge of Sn K-edge X-ray absorption near-edge structure spectra to a lower energy side as the applied voltage decreases, the decreased coordination number of Sn in the Sn-O scattering path and the presence of Sn metal contribution in the extended X-ray absorption fine structure spectra verify the reduction of SnO2 to SnOx and metallic Sn.