General approach for atomically dispersed precious metal catalysts toward hydrogen reaction

As a carbon-free energy carrier,hydrogen has become the pivot for future clean energy,while efficient hydrogen production and combustion still require precious metal-based catalysts.Single-atom catalysts(SACs)with high atomic utilization open up a desirable perspective for the scale applications of precious metals,but the general and facile preparation of various precious metal-based SACs remains challenging.Herein,a general movable printing method has been developed to synthesize various precious metal-based SACs,such as Pd,Pt,Rh,Ir,and Ru,and the features of highly dispersed single atoms with nitrogen coordination have been identified by comprehensive characterizations.More importantly,the synthesized Pt-and Ru-based SACs exhibit much higher activities than their corresponding nanoparticle counterparts for hydrogen oxidation reaction and hydrogen evolution reaction(HER).In addition,the Pd-based SAC delivers an excellent activity for photocatalytic hydrogen evolution.Especially for the superior mass activity of Ru-based SACs toward HER,density functional theory calculations confirmed that the adsorption of the hydrogen atom has a significant effect on the spin state and electronic structure of the catalysts.

Isolated Co Atoms Anchored on Defective Nitrogen-doped Carbon Graphene as Efficient Oxygen Reduction Reaction Electrocatalysts

Oxygen reduction reaction(ORR)is the heart of many new energy conversions and storage devices,such as metal-air batteries and fuel cells.However,ORR is currently facing the dilemma of sluggish intrinsic kinetics and the noble electrocatalysts of high price and low reserves.In this work,isolated Co atoms anchored on defective nitrogen-doped carbon graphene single-atom catalyst(Co-SAC/NC)are synthesized via the proposed movable type printing method.The prepared Co-SAC/NC catalyst demonstrates admirable ORR performance,with a high half-wave potential of 0.884 V in alkaline electrolytes and outstanding durability.In addition,an assembled zinc–air battery with prepared Co-SAC/NC as air-cathode catalyst displays a high-peak power density of 179 mW cm^(-2)and a high-specific capacity(757 mAh g^(-1)).Density functional theory calculations confirm that the true active sites of the prepared catalyst are Co-N_(4)moieties,and further reveal a significantly electronic structure evolution of Co sites in the ORR process,in which the project density of states and local magnetic moment of Co atom varies during its whole reaction process.This work not only paves a new avenue for synthesizing SACs as robust electrocatalysts,but also provides an electronic-level insight into the evolution of the electronic structure of single-atom catalysts.

Rational design ternary platinum based electrocatalysts for effective methanol oxidation reaction

Exploring effective, durable, and affordable electrocatalysts of methanol oxidation reaction(MOR) is of vital significance for the industrial application of direct methanol fuel cells. Herein, an efficient, general,and expandable method is developed to synthesis two-dimensional(2D) ternary Pt Bi M nanoplates(NPLs), in which various M(Co, Ni, Cu, Zn, Sn) is severed as the third component to the binary Pt Bi system. The MOR performance of Pt Bi M NPLs is entirely investigated, demonstrating that both the MOR activity and durability is enhanced with the introduction of the additional composition. Pt3Bi3Zn NPLs shows much higher MOR activity and stability than that of the Pt Bi counterparts, not to mention the current advanced Pt Ru/C and Pt/C catalysts. The prominent performances are attributed to the modulated electronic structure of the surface Pt in Pt Bi NPLs by the addition of Zn, resulting in a weakened affination between Pt and the adsorbed poisoning species(mainly CO) compared with Pt Bi NPLs, verified by density functional theory(DFT) calculations. In addition, the absorbed OH can be generated on the surface of Zn atom due to its favorable water activation properties, thus the CO removal on the adjacent Pt atoms is accelerated, further leading to a high activity and anti-poisoning performance of the resulting Pt_(3)Bi_(3)Zn catalyst. This work provides new insights and robust strategy for highly efficient MOR electrocatalyst with extraordinary anti-poisoning performance and stability.

One-dimensional PtFe hollow nanochains for the efficient oxygen reduction reaction

Integration of electronic and strain effects with tailored structures is significant to tuning the electrocatalytic activity and stability of the electrocatalysts for the oxygen reduction reaction(ORR).In this study,onedimensional PtFe hollow nanochains are synthesized by a facile and effective method,which exhibit a highly open and porous structure.The modulated electronic and strain effects of Pt atoms are verified by extensive structural characterizations,and the mass and specific activities of the prepared catalyst are roughly 7.45 and 12.44 times higher than those of the commercial Pt/C catalyst,respectively.Remarkably,the catalyst demonstrates robust performance with negligible activity decay after an accelerated durability test for 30,000 cycles.The high activity of the catalyst is probably due to the optimized absorption affinity of Pt-O accelerating the reaction kinetics induced by the cooperation of Fe atoms as well as the unique hollow and curved structures.This study provides new insights into the rational design of high-performance ORR catalysts with considerable durability.

Effects of Anodic Voltages on Microstructure and Properties of Plasma Electrolytic Oxidation Coatings on Biomedical NiTi Alloy

Plasma electrolytic oxidation （PEO） coatings, formed under various anodic voltages （320-440 V） on biomedical NiTi alloy, are mainly composed of γ-AI203 crystal phase. The evolution of discharging sparks during the PEO process under different anodic voltages was observed. The surface and cross-sectional morphologies, composition, bonding strength, wear resistance and corrosion resistance of the coatings were investigated by scanning electron microscopy （SEM）, thin-film X-ray diffraction （TF-XRD）, energy dispersive X-ray spectrometry （EDS）, surface roughness, direct pull-off test, ball-on-disk friction and wear test and potentiodynamic polarization test, respectively. The results showed that the evolution of discharging sparks during the PEO process directly influenced the microstructure of the PEO coatings and further influences the properties. When the anodic voltage increased from 320 V to 400 V, the corrosion resistance and wear resistance of the coatings slowly increased, and all the bonding strength was higher than 60 MPa; further increasing the anodic voltages, especially up to 440 V, although the thickness and γ-AI203 crystallinity of the coatings further increased, the microstructure and properties of the coatings were obviously deteriorated.

生物医用多孔Ti-15Mo合金的微波烧结制备及表面活性处理（英文）

本文采用微波烧结制备了生物医用多孔Ti-15Mo合金,并以碳酸氢铵为造孔剂调节合金孔隙率及力学性能.多孔Ti-15Mo合金是由主晶相β-Ti和少量α-Ti组成,其中α/β的比例随碳酸氢铵含量的增加无明显变化.随着碳酸氢铵含量的增加,多孔Ti-15Mo合金的孔隙率和孔径均随之增加,而抗压强度、弹性模量和抗弯强度随之下降.然而,合金的抗压强度、抗弯强度和弹性模量均高于或接近于自然骨.采用水热法对多孔Ti-15Mo合金进行表面活化处理后,多孔Ti-15Mo合金外表面和内表面均形成了针片状的Na_2Ti_6O_(13)涂层.水热处理试样经SBF溶液浸泡14天后,内外表面均完全被缺钙的磷灰石层所覆盖,说明水热处理的多孔Ti-15Mo合金具有优异的磷灰石形成能力和生物活性.由此可见,水热处理的微波烧结多孔Ti-15Mo合金是一种非常有前途的骨植入材料.