NiFe-based electrocatalysts have attracted great interests due to the lowp rice and high activity in oxygen evolution reaction (OER). However,t he complex reaction mechanism of NiFe-catalyzedOER has not been fully explored yet. Detection of intermediate species can bridge the gap between OER performances and catalyst component/structure properties.H ere,w ep erformed label-free surface-enhanced Raman spectroscopic (SERS) monitoring of interfacial OER process on Ni 3 FeO x nanoparticles (NPs) in alkaline medium. By using bifunctional Au@Ni 3 FeO x core-satellite superstructures as Raman signal enhancer,wefound direct spectroscopic evidence of intermediate O-O À species.According to the SERS results,Featoms are the catalytic sites for the initial OH À to O-O À oxidation. The O-O À species adsorbed across neighboring Fe and Ni sites experiences further oxidation caused by electron transfer to Ni III and eventually forms O 2 product.

Nowadays, lithium-ion batteries (LIBs) have been widely used in portable electronics, electric vehicles, and grid energy storage systems. [1][2][3] However, the traditional LIBs based on graphite anode cannot satisfy the ever growing energy density demands. [4,5] In this background, next-generation Li-ion batteries based on Li metal anode with ultrahigh energy density have attracted worldwide attention in recent years, such as lithium-sulfur (2600 Wh kg −1 ), Li-O 2 batteries (3580 Wh kg −1 ). [6][7][8] Li metal anode with high theoretical specific capacity (3860 mAh g −1 ), low density (0.534 g cm −3 ), and the lowest potential (−3.040 V vs standard hydrogen electrode) demonstrated remarkable advantages in energy density as anode for Li metal batteries (LMBs). [9][10][11][12][13][14] However, the practical application of Li metal anode in LMBs is still suffering from low coulombic efficiency (CE), poor cycle life, and safety concerns because of serious Li dendrite growth during cycling. [15][16][17] The uncontrollable dendrite growth leads to the formation of "dead lithium" with low coulombic efficiency, and may even cause catastrophic failure of battery by internal short circuit. [18][19][20] During the past decade, there are majorly two kinds of strategies proposed to suppress dendrite growth and protect lithium metal anode. The first approach is based on a mechanical blocking strategy, such as, 1) optimization of the solid electrolyte interface (SEI) layer and improving its mechanical modulus and stability, for which LiF, [21][22][23] Li 3 N, [24] Li 2 S, [25][26][27] Li 3 PO 4 , [28] Li 2 O, [29] etc. have been introduced into the SEI layer and showed an improved cycling performance at 1.0-2.0 mA cm −2 ; 2) introducing an extra coating layer (poly(dimethylsiloxane), [30] hollow carbon spheres, [31] artificial solid electrolyte layer, [32] etc.) as a protecting layer on the surface of Li metal. The other approach is focused on designing various nanostructures to control the electric field distribution and accommodate volume expansion. In which, hierarchical frameworks such as 3D carbon fiber cloth, [33] Ni foam, [34] and 3D porous Cu foil [35,36] have been constructed to store Li metal and inhibit the growth of Li dendrites. However, these two strategies were both converged at inhibiting lithium deposition, which have not changed the fundamental, self-amplification behavior of the dendrite growth. Moreover, they failed to support the practical application of Li-S or Li-O 2 Uncontrollable Li dendrite growth and low Coulombic efficiency severely hinder the application of lithium metal batteries. Although a lot of approaches have been developed to control Li deposition, most of them are based on inhibiting lithium deposition on protrusions, which can suppress Li dendrite growth at low current density, but is inefficient for practical battery applications, with high current density and large area capacity. Here, a novel leveling mechanism based on accelerating Li growth in concave fashion is proposed, which ena...

Doped carbon materials (DCM) with multiple heteroatoms hold broad interest in electrochemical catalysis and energy storage but require several steps to fabricate, which greatly hinder their practical applications. In this study, a facile strategy is developed to enable the fast fabrication of multiply doped carbon materials via room-temperature dehalogenation of polyvinyl dichloride (PVDC) promoted by KOH with the presence of different organic dopants. A N,S-codoped carbon material (NS-DCM) is demonstratively synthesized using two dopants (dimethylformamide for N doping and dimethyl sulfoxide for S doping). Afterward, the precursive room-temperature NS-DCM with intentionally overdosed KOH is submitted to inert annealing to obtain large specific surface area and high conductivity. Remarkably, NS-DCM annealed at 600 °C (named as 600-NS-DCM), with 3.0 atom % N and 2.4 atom % S, exhibits a very high specific capacitance of 427 F g at 1.0 A g in acidic electrolyte and also keeps ∼60% of capacitance at ultrahigh current density of 100.0 A g. Furthermore, capacitive deionization (CDI) measurements reveal that 600-NS-DCM possesses a large desalination capacity of 32.3 mg g (40.0 mg L NaCl) and very good cycling stability. Our strategy of fabricating multiply doped carbon materials can be potentially extended to the synthesis of carbon materials with various combinations of heteroatom doping for broad electrochemical applications.

The crumpled graphene (CrG) was fabricated by applying defluorination of polyvinylidenefluoride (PVDF) on highly curved surface of CaC2 particle through bottom-up synthetic strategy. The limited reaction depth between PVDF and CaC2 leads to the formation of CrG with thin layer (3−6 layer graphene) and reasonable high specific surface area (~324.8 m 2 g −1 ). CrG with N incorporation (N-CrG) was applied as electrode material for reducing oxygen (i.e., oxygen reduction reaction, ORR) in alkaline, showing close onset potential to that of Pt/C and better mass-diffusion behavior. Surprisingly, with increased mass loading of catalysts, N-CrG exhibits steady current increase while Pt/C shows clear current plateau. Meanwhile, the N-CrG sample reveals high cycling stability and tolerance to contaminant, demonstrating its high potential for practical applications. Additionally, the bottom-up synthetic pathway to CrG via polymer dehalogenation on solid alkaline may find more applications which require controlled morphology and thickness of deposited thin graphitic carbon layers.