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A vertically aligned carbon nanofiber (VACNF) array with unique conically stacked graphitic structure directly grown on a planar Cu current collector (denoted as VACNF/Cu) is used as a high-porosity 3D host to overcome the commonly encountered issues of Li metal anodes. The excellent electrical conductivity and highly active lithiophilic graphitic edge sites facilitate homogenous coaxial Li plating/stripping around each VACNF and forming a uniform solid electrolyte interphase. The high specific surface area effectively reduces the local current density and suppresses dendrite growth during the charging/discharging processes. Meanwhile, this open nanoscale vertical 3D structure eliminates the volume changes during Li plating/stripping. As a result, highly reversible Li plating/stripping with high coulombic efficiency has been achieved at various current densities. A low voltage hysteresis of 35 mV over 500 h in symmetric cells has been achieved at 1 mA cm-2 with an areal Li plating capacity of 2 mAh cm-2 , which is far superior to the planar Cu current collector. Furthermore, a Li-S battery using a S@PAN cathode and a lithium-plated VACNF/Cu (VACNF/Cu@Li) anode with slightly higher capacity (2 mAh cm-2) exhibits an excellent rate capability and high cycling stability with no capacity fading over 600 cycles. Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff))

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Single-atom catalysts have expanded the design paradigm for oxygen reduction reaction (ORR) relying on nonplatinum group metals (non-PGM). Here, density functional theory calculations were performed on a variety of dual-metal active centers, consisting of both PGM (Pt and Pd) and non-PGM (Fe, Co, Ni, and Cu) metals, embedded in a monolayer of graphene and coordinated by six pyridinic nitrogen atoms. The dual-metal site stability, OH ligand effect, and electronic structures relevant to ORR were investigated. The ORR reactivities can be depicted in terms of a volcano diagram divided into multiple potential limiting regimes based on a wide range of ΔG OH* values. In addition to OH removal and free molecular O 2 protonation as the potential-limiting steps, the protonation of adsorbed O 2 and O also emerge as likely potential-limiting steps due to strong O 2 adsorptions at certain dual-metal active sites. Among the systems investigated, Fe−Co(OH) s exhibits the highest activity. Moreover, other PGM-free dual-metal sites such as Fe−Fe(OH), Fe−Cu(OH), and Co−Co(OH) also appear to be competitive and would encourage further explorations for Pt-free ORR electrocatalyst alternatives.