Fabrication of three-dimensional copper nanodomes as anode materials for direct methanol fuel cells

In this study, we demonstrate a novel approach for fabricating copper nanodomes (Cu-NDs) by combining of soft lithography, nanosphere lithography, physical vapor deposition (PVD) and electrochemical deposition methods. The 3D nano structures were characterized using surface microscopic techniques. The methanol oxidation activity of the Cu-NDs anode was tested by electrochemical methods in 0.1 M KOH +1 M CH₃OH solution and the results were compared with that of bulk Cu as a reference point. The results showed that very well-structured, uniformly and homogeneously distributed Cu-NDs could be fabricated using these combined methods. The peak current density related to methanol oxidation reaction increased and charge transfer resistance reduced almost three times at the Cu-NDs electrode with respect to the bulk Cu. Also, the Cu-NDs electrode has good time stability and high tolerance to CO_ads poisoning. The enhanced activity of the nanostructures was related to good intrinsic activity of Cu for this reaction and their larger available electrochemical active sites.     

Spin-Related Electron Transfer and Orbital Interactions in Oxygen Electrocatalysis

Oxygen evolution and reduction reactions play a critical role in determining the efficiency of the water cycling (H₂O ⇔ H₂ + $\frac{1}{2}$O₂), in which the hydrogen serves as the energy carrier. That calls for a comprehensive understanding of oxygen electrocatalysis for efficient catalyst design. Current opinions on oxygen electrocatalysis have been focused on the thermodynamics of the reactant/intermediate adsorption on the catalysts. Because the oxygen molecule is paramagnetic, its production from or its reduction to diamagnetic hydroxide/water involves spin-related electron transfer. Both electron transfer and orbital interactions between the catalyst and the reactant/intermediate show spin-dependent character, making the reaction kinetics and thermodynamics sensitive to the spin configurations. Herein, a brief introduction on the spintronic explanation of the catalytic phenomena on oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is given. The local spin configurations and orbital interactions in the benchmark transition-metal-based catalysts for OER and ORR are analyzed as examples. To further understand the spintronic oxygen electrocatalysis and to develop more efficient spintronic catalysts, the challenges are summarized and future opportunities proposed. Spin electrocatalysis may emerge as an important topic in the near future and help integrate a comprehensive understanding of oxygen electrocatalysis.     

Transition metal chalcogenide anodes for sodium storage

Owing to the low cost and indefinite availability of sodium resources, rechargeable sodium-ion batteries (SIBs) are now being considered as the most appealing alternatives to their lithium-ion counterparts for large scale applications. On the other hand, transition metal chalcogenides (TMCs) have emerged as potential candidates of SIB anodes due to their versatile material species, ample abundance, low cost, robust nature and high theoretical capacities. However, TMCs still face several challenges like severe volume changes during sodiation/desodiation, inadequate conductivities and large-scale productions. Hence, many traditional and unconventional techniques have been developed to mitigate these issues and obtain high quality electrode materials for practical applications. In this review, recent progress and the rectification stratagems of the problems of TMCs have been summarized firstly. Then, a detailed comparison of transition metal selenides with sulfide TMCs family members was provided to investigate the factors which govern the relative performance improvements of selenides. Besides this, multiple transition metals containing TMCs (M-TMCs) have exhibited intriguingly better performances compared to mono-metal TMCs. Hence, various inspirational features of M-TMCs were discussed. As an outcome of these discussions, we were able to outline several outlooks and prospective solutions for the rectification of potential challenges of TMC anode materials.