Electron Localization in Rationally Designed Pt1Pd Single-Atom Alloy Catalyst Enables High-Performance Li-O2 Batteries.

Li-O2 batteries (LOBs) are considered as one of the most promising energy storage devices due to their ultrahigh theoretical energy density, yet they face the critical issues of sluggish cathode redox kinetics during the discharge and charge processes. Here we report a direct synthetic strategy to fabricate a single-atom alloy catalyst in which single-atom Pt is precisely dispersed in ultrathin Pd hexagonal nanoplates (Pt1Pd). The LOB with the Pt1Pd cathode demonstrates an ultralow overpotential of 0.69 V at 0.5 A g-1 and negligible activity loss over 600 h. Density functional theory calculations show that Pt1Pd can promote the activation of the O2/Li2O2 redox couple due to the electron localization caused by the single Pt atom, thereby lowering the energy barriers for the oxygen reduction and oxygen evolution reactions. Our strategy for designing single-atom alloy cathodic catalysts can address the sluggish oxygen redox kinetics in LOBs and other energy storage/conversion devices.

Quasi-Solid Sulfur Conversion for Energetic All-Solid-State Na-S Battery.

The high theoretical energy density (1274 Wh kg-1) and high safety enable the all-solid-state Na-S batteries with great promise for stationary energy storage system. However, the uncontrollable solid-liquid-solid multiphase conversion and its associated sluggish polysulfides redox kinetics pose a great challenge in tunning the sulfur speciation pathway for practical Na-S electrochemistry. Herein, we propose a new design methodology for matrix featuring separated bi-catalytic sites that control the multi-step polysulfide transformation in tandem and direct quasi-solid reversible sulfur conversion during battery cycling. It is revealed that the N, P heteroatom hotspots are more favorable for catalyzing the long-chain polysulfides reduction, while PtNi nanocrystals manipulate the direct and full Na2S4 to Na2S low-kinetic conversion during discharging. The electrodeposited Na2S on strongly coupled PtNi and N, P-codoped carbon host is extremely electroreactive and can be readily recovered back to S8 without passivation of active species during battery recharging, which delivers a true tandem electrocatalytic quasi-solid sulfur conversion mechanism. Accordingly, stable cycling of the all-solid-state soft-package Na-S pouch cells with an attractive specific capacity of 876 mAh gS -1 and a high energy of 608 Wh kgcathode -1 (172 Wh kg-1, based on the total mass of cathode and anode) at 60 °C are demonstrated.

Dual-Atom Support Boosts Nickel-Catalyzed Urea Electrooxidation.

Nickel-based catalysts have been regarded as one of the most promising electrocatalysts for urea oxidation reaction (UOR), however, their activity is largely limited by the inevitable self-oxidation reaction of Ni species (NSOR) during the UOR. Here, we proposed an interface chemistry modulation strategy to trigger the occurrence of UOR before the NSOR via constructing a 2D/2D heterostructure that consists of ultrathin NiO anchored Ru-Co dual-atom support (Ru-Co DAS/NiO). Operando spectroscopic characterizations confirm this unique triggering mechanism on the surface of Ru-Co DAS/NiO. Consequently, the fabricated catalyst exhibits outstanding UOR activity with a low potential of 1.288 V at 10 mA cm-2 and remarkable long-term durability for more than 330 h operation. DFT calculations and spectroscopic characterizations demonstrate that the favorable electronic structure induced by this unique heterointerface endows the catalyst energetically more favorable for the UOR than the NSOR.

Single-Atom Yttrium Engineering Janus Electrode for Rechargeable Na-S Batteries.

The development of rechargeable Na-S batteries is very promising, thanks to their considerably high energy density, abundance of elements, and low costs and yet faces the issues of sluggish redox kinetics of S species and the polysulfide shuttle effect as well as Na dendrite growth. Following the theory-guided prediction, the rare-earth metal yttrium (Y)-N4 unit has been screened as a favorable Janus site for the chemical affinity of polysulfides and their electrocatalytic conversion, as well as reversible uniform Na deposition. To this end, we adopt a metal-organic framework (MOF) to prepare a single-atom hybrid with Y single atoms being incorporated into the nitrogen-doped rhombododecahedron carbon host (Y SAs/NC), which features favorable Janus properties of sodiophilicity and sulfiphilicity and thus presents highly desired electrochemical performance when used as a host of the sodium anode and the sulfur cathode of a Na-S full cell. Impressively, the Na-S full cell is capable of delivering a high capacity of 822 mAh g-1 and shows superdurable cyclability (97.5% capacity retention over 1000 cycles at a high current density of 5 A g-1). The proof-of-concept three-dimensional (3D) printed batteries and the Na-S pouch cell validate the potential practical applications of such Na-S batteries, shedding light on the development of promising Na-S full cells for future application in energy storage or power batteries.

Engineering Water Molecules Activation Center on Multisite Electrocatalysts for Enhanced CO2 Methanation.

The renewable energy-powered electrolytic reduction of carbon dioxide (CO2) to methane (CH4) using water as a reaction medium is one of the most promising paths to store intermittent renewable energy and address global energy and sustainability problems. However, the role of water in the electrolyte is often overlooked. In particular, the slow water dissociation kinetics limits the proton-feeding rate, which severely damages the selectivity and activity of the methanation process involving multiple electrons and protons transfer. Here, we present a novel tandem catalyst comprising Ir single-atom (Ir1)-doped hybrid Cu3N/Cu2O multisite that operates efficiently in converting CO2 to CH4. Experimental and theoretical calculation results reveal that the Ir1 facilitates water dissociation into proton and feeds to the hybrid Cu3N/Cu2O sites for the *CO protonation pathway toward *CHO. The catalyst displays a high Faradaic efficiency of 75% for CH4 with a current density of 320 mA cm-2 in the flow cell. This work provides a promising strategy for the rational design of high-efficiency multisite catalytic systems.

Ru-Co Pair Sites Catalyst Boosts the Energetics for the Oxygen Evolution Reaction.

Manipulating the coordination environment of the active center via anion modulation to reveal tailored activity and selectivity has been widely achieved, especially for carbon-based single-atom site catalysts (SACs). However, tuning ligand fields of the active center by single-site metal cation regulation and identifying the effects on the resulting electronic configuration is seldom explored. Herein, we propose a single-site Ru cation coordination strategy to engineer the electronic properties by constructing a Ru/LiCoO2 SAC with atomically dispersed Ru-Co pair sites. Benefitting from the strong electronic coupling between Ru and Co sites, the catalyst possesses an enhanced electrical conductivity and achieves near-optimal oxygen adsorption energies. Therefore, the optimized catalyst delivers superior oxygen evolution reaction (OER) activity with low overpotential, the high mass activity of 1000 A goxide -1 at a small overpotential of 335 mV, and excellent long-term stability. It also exhibits rapid kinetics with superior rate capability and outstanding durability in a zinc-air battery.

Engineering the Local Atomic Environments of Indium Single-Atom Catalysts for Efficient Electrochemical Production of Hydrogen Peroxide.

The in-depth understanding of local atomic environment-property relationships of p-block metal single-atom catalysts toward the 2 e- oxygen reduction reaction (ORR) has rarely been reported. Here, guided by first-principles calculations, we develop a heteroatom-modified In-based metal-organic framework-assisted approach to accurately synthesize an optimal catalyst, in which single In atoms are anchored by combined N,S-dual first coordination and B second coordination supported by the hollow carbon rods (In SAs/NSBC). The In SAs/NSBC catalyst exhibits a high H2 O2 selectivity of above 95 % in a wide range of pH. Furthermore, the In SAs/NSBC-modified natural air diffusion electrode exhibits an unprecedented production rate of 6.49 mol peroxide gcatalyst -1 h-1 in 0.1 M KOH electrolyte and 6.71 mol peroxide gcatalyst -1 h-1 in 0.1 M PBS electrolyte. This strategy enables the design of next-generation high-performance single-atom materials, and provides practical guidance for H2 O2 electrosynthesis.

Highly Selective Photoreduction of CO2 with Suppressing H2 Evolution by Plasmonic Au/CdSe-Cu2 O Hierarchical Nanostructures under Visible Light.

Here, the photocatalytic CO2 reduction reaction (CO2 RR) with the selectivity of carbon products up to 100% is realized by completely suppressing the H2 evolution reaction under visible light (λ > 420 nm) irradiation. To target this, plasmonic Au/CdSe dumbbell nanorods enhance light harvesting and produce a plasmon-enhanced charge-rich environment; peripheral Cu2 O provides rich active sites for CO2 reduction and suppresses the hydrogen generation to improve the selectivity of carbon products. The middle CdSe serves as a bridge to transfer the photocharges. Based on synthesizing these Au/CdSe-Cu2 O hierarchical nanostructures (HNSs), efficient photoinduced electron/hole (e- /h+ ) separation and 100% of CO selectivity can be realized. Also, the 2e- /2H+ products of CO can be further enhanced and hydrogenated to effectively complete 8e- /8H+ reduction of CO2 to methane (CH4 ), where a sufficient CO concentration and the proton provided by H2 O reduction are indispensable. Under the optimum condition, the Au/CdSe-Cu2 O HNSs display high photocatalytic activity and stability, where the stable gas generation rates are 254 and 123 µmol g-1 h-1 for CO and CH4 over a 60 h period.

Bismuth Single Atoms Resulting from Transformation of Metal-Organic Frameworks and Their Use as Electrocatalysts for CO2 Reduction.

The electrocatalytic reduction reaction of CO2 (CO2RR) is a promising strategy to promote the global carbon balance and combat global climate change. Herein, exclusive Bi-N4 sites on porous carbon networks can be achieved through thermal decomposition of a bismuth-based metal-organic framework (Bi-MOF) and dicyandiamide (DCD) for CO2RR. Interestingly, in situ environmental transmission electron microscopy (ETEM) analysis not only directly shows the reduction from Bi-MOF into Bi nanoparticles (NPs) but also exhibits subsequent atomization of Bi NPs assisted by the NH3 released from the decomposition of DCD. Our catalyst exhibits high intrinsic CO2 reduction activity for CO conversion, with a high Faradaic efficiency (FECO up to 97%) and high turnover frequency of 5535 h-1 at a low overpotential of 0.39 V versus reversible hydrogen electrode. Further experiments and density functional theory results demonstrate that the single-atom Bi-N4 site is the dominating active center simultaneously for CO2 activation and the rapid formation of key intermediate COOH* with a low free energy barrier.

Unleashing the high energy potential of zinc-iodide batteries: high-loaded thick electrodes designed with zinc iodide as the cathode.

The realization of high energy is of great importance to unlock the practical potential of zinc-iodine batteries. However, significant challenges, such as low iodine loading (mostly less than 50 wt%), restricted iodine reutilization, and severe structural pulverization during cycling, compromise its intrinsic features. This study introduces an optimized, fully zincified zinc iodide loaded onto a hierarchical carbon scaffold with high active component loading and content (82 wt%) to prepare a thick cathode for enabling high-energy Zn-I2 batteries. The synergistic interactions between nitrogen heteroatoms and cobalt nanocrystals within the porous matrix not only provide forceful chemisorption to lock polyiodide intermediates but also invoke the electrocatalytic effects to manipulate efficient iodine conversion. The ZnI2 cathode could effectively alleviate continuous volumetric expansion and maximize the utilization of active species. The electrochemical examinations confirm the thickness-independent battery performance of assembled Zn-I2 cells due to the ensemble effect of composite electrodes. Accordingly, with a thickness of 300 µm and ZnI2 loading of up to 20.5 mg cm-2, the cathode delivers a specific capacity of 92 mA h gcathode-1 after 2000 cycles at 1C. Moreover, the Zn-I2 pouch cell with ZnI2 cathode has an energy density of 145 W h kgcathode-1 as well as a stable long cycle life.

Out-of-plane coordination of iridium single atoms with organic molecules and cobalt-iron hydroxides to boost oxygen evolution reaction.

Advancements in single-atom-based catalysts are crucial for enhancing oxygen evolution reaction (OER) performance while reducing precious metal usage. A comprehensive understanding of underlying mechanisms will expedite this progress further. Here we report Ir single atoms coordinated out-of-plane with dimethylimidazole (MI) on CoFe hydroxide (Ir1/(Co,Fe)-OH/MI). This Ir1/(Co,Fe)-OH/MI catalyst, which was prepared using a simple immersion method, delivers ultralow overpotentials of 179 mV at a current density of 10 mA cm-2 and 257 mV at 600 mA cm-2 as well as an ultra-small Tafel slope of 24 mV dec-1. Furthermore, Ir1/(Co,Fe)-OH/MI has a total mass activity exceeding that of commercial IrO2 by a factor of 58.4. Ab initio simulations indicate that the coordination of MI leads to electron redistribution around the Ir sites. This causes a positive shift in the d-band centre at adjacent Ir and Co sites, facilitating an optimal energy pathway for OER.

Ir-Sn pair-site triggers key oxygen radical intermediate for efficient acidic water oxidation.

The anode corrosion induced by the harsh acidic and oxidative environment greatly restricts the lifespan of catalysts. Here, we propose an antioxidation strategy to mitigate Ir dissolution by triggering strong electronic interaction via elaborately constructing a heterostructured Ir-Sn pair-site catalyst. The formation of Ir-Sn dual-site at the heterointerface and the resulting strong electronic interactions considerably reduce d-band holes of Ir species during both the synthesis and the oxygen evolution reaction processes and suppress their overoxidation, enabling the catalyst with substantially boosted corrosion resistance. Consequently, the optimized catalyst exhibits a high mass activity of 4.4 A mgIr-1 at an overpotential of 320 mV and outstanding long-term stability. A proton-exchange-membrane water electrolyzer using this catalyst delivers a current density of 2 A cm-2 at 1.711 V and low degradation in an accelerated aging test. Theoretical calculations unravel that the oxygen radicals induced by the π* interaction between Ir 5d-O 2p might be responsible for the boosted activity and durability.

Synergistically Modulating Geometry and Electronic Structures of a Chalcogenide Photocatalyst via an Ion-Exchange Strategy.

Maneuvering the architecture and composition of semiconductors is essential to optimizing their performance in photocatalytic solar-to-fuel conversion. Here, we show that ion exchange, having a disparate mechanism with direct nucleation and growth of semiconductor crystals, can provide a new platform for rational control over the geometry and electronic structures of chalcogenide semiconductor photocatalysts. As a demonstration, the ZnSe nanocubes possessing a hollowed architecture and doped with a controllable amount of Ag+ ions are accessed via sequential ion exchange. The kinetics of the exchange reaction offers a knob for regulating the electronic structures of the Ag-doped ZnSe hollow cubes and, hence, their functions in light harvesting and photogenerated charge separation. Such synergistically geometric and optoelectronic modulation of ZnSe brings an order of magnitude enhancement in photocatalytic H2 evolution activity relative to commercial ZnSe powders. Our study corroborates that ion exchange may open up new horizons for judicious fabrication and engineering of semiconductor-based photocatalyst materials.

Controlled Synthesis of Co@N-Doped Carbon by Pyrolysis of ZIF with 2-Aminobenzimidazole Ligand for Enhancing Oxygen Reduction Reaction and the Application in Zn-Air Battery.

The Co/N-doped carbon material, as an important electrocatalytic material, has been attracted intense interest in ORR and Zn-air battery. Here, we report an efficient Co@N-doped carbon catalyst (Co@N-C-1) obtained by pyrolysis of ZIF precursor with 2-aminobenzimidazole. The introduction of 2-aminobenzimidazole results in the formation of hierarchical meso/microporous structure of the as-prepared Co@N-C-1, effectively avoiding the aggregation of Co nanoparticles during pyrolysis and the higher N content, which contributes to enhance the ORR electrocatalytic activities. The obtained Co@N-C-1 exhibits remarkable ORR performance with a half-wave potential of 0.938 V vs RHE in alkaline media. As the air catalyst of zinc-air batteries, Co@N-C-1 displays 1.439 V of open-circuit voltage and 1413.3 Wh·kg-1 of energy density.

Porous platinum-silver bimetallic alloys: surface composition and strain tunability toward enhanced electrocatalysis.

Promoting surface strains in heterogeneous catalysts and heteroatomic interactions in alloying offer an effective strategy for the development of electrocatalysts with greatly enhanced activity. In this work, we design platinum-silver nanotubes (PtAg NTs) with tunable surface compositions by a controlled galvanic replacement reaction of well-defined Ag nanowires (NWs). The optimized and porous PtAg NTs (PtAg-4 NTs), with the Pt5Ag3 surface composition and (111) facet-dominant surface features, exhibit an extraordinary oxygen reduction reaction (ORR) activity that reaches a specific activity of 1.13 mA cm-2 and a mass activity of 0.688 A mg-1Pt at 0.9 V versus a reversible hydrogen electrode (RHE), which are 4.5 times and 4.3 times those of commercial Pt/C catalysts (0.25 mA cm-2 and 0.16 A mg-1Pt). Moreover, PtAg-4 NTs/C can endure under the ORR conditions over the course of 10 000 cycles with negligible activity decay. Remarkably, density functional theory simulations reveal that the porous PtAg-4 NTs exhibit enhanced adsorption interaction with adsorbates, attributed to the catalytically active sites on high-density (111) facets and modulation of the surface strain, further boosting the ORR activity and durability.

Porous Co3O4 hollow nanododecahedra for nonenzymatic glucose biosensor and biofuel cell.

Cobalt oxide hollow nanododecahedra (Co3O4-HND) is synthesized by a facile thermal transformation of cobalt-based metal-organic framework (Co-MOF, ZIF-67) template. The morphology and properties of the Co3O4-HND are characterized by a set of techniques, including transmission electron microscope (TEM), powder X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunner-Emmet-Teller (BET). When tested as a non-enzymatic electrocatalyst for glucose oxidation reaction, the Co3O4-HND exhibits a high activity and shows an outstanding performance for determining glucose with a wide window of 2.0µM to 6.06mM, a high sensitivity of 708.4µAmM(-1)cm(-2), a low detection limit of 0.58µM (S/N=3), and fast response time(<2s). Based on the nonenzymatic oxidation of glucose, Co3O4-HND could be served as an attractive non-enzyme and noble-metal-free electrocatalyst in glucose fuel cell (GFC) due to its excellent electrochemical properties, low cost and facile preparation.