A highly selective and durable electrocatalyst for carbon dioxide (CO2) conversion to formate is developed, consisting of tin (Sn) nanosheets decorated with bismuth (Bi) nanoparticles. Owing to the formation of active sites through favorable orbital interactions at the Sn‐Bi interface, the Bi‐Sn bimetallic catalyst converts CO2 to formate with a remarkably high Faradaic efficiency (96%) and production rate (0.74 mmol h−1 cm−2) at −1.1 V versus reversible hydrogen electrode. Additionally, the catalyst maintains its initial efficiency over an unprecedented 100 h of operation. Density functional theory reveals that the addition of Bi nanoparticles upshifts the electron states of Sn away from the Fermi level, allowing the HCOO* intermediate to favorably adsorb onto the Bi‐Sn interface compared to a pure Sn surface. This effectively facilitates the flow of electrons to promote selective and durable conversion of CO2 to formate. This study provides sub‐atomic level insights and a general methodology for bimetallic catalyst developments and surface engineering for highly selective CO2 electroreduction.

Combining the advantages of homogeneous and heterogeneous catalysts,s ingle-atom catalysts (SACs) are bringing new opportunities to revolutionizeO RR catalysis in terms of cost, activity and durability.However,the lack of highperformance SACs as well as the fundamental understanding of their unique catalytic mechanisms call for serious advances in this field. Herein, for the first time,w ed evelop an Ir-N-C single-atom catalyst (Ir-SAC) whichm imics homogeneous iridium porphyrins for high-efficiency ORR catalysis.I na ccordance with theoretical predictions,the as-developed Ir-SAC exhibits orders of magnitude higher ORR activity than iridium nanoparticles with arecord-high turnover frequency (TOF) of 24.3 e À site À1 s À1 at 0.85 Vv s. RHE) and an impressive mass activity of 12.2 Amg À1 Ir ,which far outperforms the previously reported SACs and commercial Pt/C.A tomic structural characterizations and density functional theory calculations reveal that the high activity of Ir-SACi sa ttributed to the moderate adsorption energy of reaction intermediates on the mononuclear iridium ion coordinated with four nitrogen atom sites.

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electronic insulator with abundant oxygen-containing groups (epoxy, hydroxyl, and carboxyl groups), which can be easily functionalized to improve its ionic conductivity. [12,16] Owing to the wide range of oxygen functional groups on its basal planes and edges, GO is also readily exfoliated to yield well-dispersed solution of individual GO sheets in both water and organic solvents, and then flow-directed assembled into a free-standing paper-like material by vacuum filtration. [12,17] However, despite all the progress of the development of a free-standing GO electrolyte membrane, its advantages are diminished with the difficulty to form a mechanically robust membrane. [17,18] Consequently, that makes the free-standing GO membranes less attractive for being used as practical solid-state electrolytes in energy storage systems. To enhance the mechanical strength, several fillers can be incorporated into GO matrix. Among the multifarious materials, cellulose-the most abundant renewable material-is recognized as a good binder and surface modifier thanks to its low cost, high hygroscopicity, flexibility, ad porous substrate that allows strong binding of other materials. Particularly, considerable interest has been directed to nanocellulose fiber because of its low thermal expansion, high surface area, high surface area-to-volume ratio, strengthening effect, good mechanical and optical properties which may find many applications in nanocomposites. [19] Meanwhile, due to its highly reactive area rich in hydroxyl groups, cellulose can be easily refashioned through a surface-functionalization to conduct ions and be utilized in advanced batteries. [7] Herein, for the first time, we report on a laminate-structured nanocellulose/GO membrane functionalized with highly hydroxide-conductive quaternary ammonium (QA) groups to be applied as a robust solid-state electrolyte in flexible, rechargeable zinc-air batteries. The QA-functionalized nanocellulose/GO (QAFCGO) membrane is fabricated through chemical functionalization, layer-by-layer filtration, cross-linking, and ion-exchange processes (Figure 1a). For the functionalization process, dimethyloctadecyl [3-(trimethoxysilyl)-propyl] ammonium chloride (DMAOP) has been selected as the functional precursor containing QA moieties. The hydroxide conductivity and the alkaline stability in the highly surface-active DMAOP are provided by quaternary ammonium groups which are already attached to this organic compound. Thus, the hydroxide conducting characteristic of the electrolyte membrane can be achieved directly through the precursor DMAOP without complex organic synthesis. First, the trimethoxy groups of trimethoxysilyl are hydrolyzed to form the corresponding silanols, and the hydrolyzed silanols undergo self-condensation to yield silanol oligomers intermediates ( Figure S1, step 1, Supporting Information). Then, these intermediates are adsorbed onto nanocellulose/GO surface rich in oxygen-containing groups through hydrogen bonding ( Figure S1,

Rechargeable zinc–air batteries (ZnABs) are attracting great interest due to their high theoretical specific energy, safety, and economic viability. However, their performance and large‐scale practical applications are largely limited by poor durability and high overpotential on the air‐cathode due to the slow kinetics of the oxygen reduction and evolution reactions (ORR/OER). Therefore, it is highly desired to exploit an ideal bifunctional catalyst to endow the obtained ZnABs with excellent ORR/OER catalytic performances. Herein, a new nonprecious‐metal bifunctional catalyst of urchin‐like NiCo2S4 microsphere synergized with sulfur‐doped graphene nanosheets (S‐GNS/NiCo2S4) is controllably designed and synthesized by simply tailoring the structure and electronic arrangement, which endow the as‐prepared catalyst with excellent electroactivity and long‐term durability toward ORR and OER. Importantly, ZnABs constructed by this outstanding catalyst exhibit high power density, small charge/discharge voltage gap, and excellent cycle stability, notably outperforming the more costly commercial Pt/C + Ir/C mixture catalyst. These excellent electrocatalytic performances together with the simplicity of the synthetic method, make the urchin‐like NiCo2S4 microsphere/S‐GNS hybrid nanostructure exhibit great promise as a superior air‐cathode catalyst for high‐performance rechargeable ZnABs.

A hybrid alkaline zinc–iodine redox flow battery has been designed with an unprecedented energy density record to date for an all-aqueous redox flow battery.

Rich, porous graphene frameworks decorated with uniformly dispersed active sites are prepared by using polyaniline as a graphene precursor and introducing phenanthroline as a pore-forming agent. The unprecedented fuel-cell performance of this electrocatalyst is linked to the graphene frameworks with vast distribution of pore sizes, which maximizes the active-sites accessibility, facilitates mass-transport properties, and improves the carbon corrosion resistance.

Transition metal atoms with corresponding nitrogen coordination are widely proposed as catalytic centers for the oxygen reduction reaction (ORR) in metal–nitrogen–carbon (M–N–C) catalysts. Here, an effective strategy that can tailor Fe–N–C catalysts to simultaneously enrich the number of active sites while boosting their intrinsic activity and utilization is reported. This is achieved by edge engineering of FeN4 sites via a simple ammonium chloride salt‐assisted approach, where a high fraction of FeN4 sites are preferentially generated and hosted in a graphene‐like porous scaffold. Theoretical calculations reveal that the FeN4 moieties with adjacent pore defects are likely to be more active than the nondefective configuration. Coupled with the facilitated accessibility of active sites, this prepared catalyst, when applied in a practical H2–air proton exchange membrane fuel cell, delivers a remarkable peak power density of 0.43 W cm−2, ranking it as one of the most active M–N–C catalysts reported to date. This work provides a new avenue for boosting ORR activity by edge manipulation of FeN4 sites.