Optimizing 3d spin polarization of CoOOH by in situ Mo doping for efficient oxygen evolution reaction

Transition-metal oxyhydroxides are attractive catalysts for oxygen evolution reactions(OERs).Further studies for developing transition-metal oxyhydroxide catalysts and understanding their catalytic mechanisms will benefit their quick transition to the next catalysts.Herein,Mo-doped CoOOH was designed as a high-performance model electrocatalyst with durability for 20 h at 10 mAcm−2.Additionally,it had an overpotential of 260 mV(glassy carbon)or 215 mV(nickel foam),which was 78 mV lower than that of IrO_(2)(338 mV).In situ,Raman spectroscopy revealed the transformation process of CoOOH.Calculations using the density functional theory showed that during OER,doped Mo increased the spin-up density of states and shrank the spin-down bandgap of the 3d orbits in the reconstructed CoOOH under the electrochemical activation process,which simultaneously optimized the adsorption and electron conduction of oxygen-related intermediates on Co sites and lowered the OER overpotentials.Our research provides new insights into the methodical planning of the creation of transition-metal oxyhydroxide OER catalysts.

Building stabilized Cu_(0.17)Mn_(0.03)V_(2)O_(5−□)·2.16H_(2)O cathode enables an outstanding room‐/low‐temperature aqueous Zn‐ion batteries

Vanadium oxide cathode materials with stable crystal structure and fast Zn^(2+) storage capabilities are extremely important to achieving outstanding electrochemical performance in aqueous zinc‐ion batteries.In this work,a one‐step hydrothermal method was used to manipulate the bimetallic ion intercalation into the interlayer of vanadium oxide.The pre‐intercalated Cu ions act as pillars to pin the vanadium oxide(V‐O)layers,establishing stabilized two‐dimensional channels for fast Zn^(2+) diffusion.The occupation of Mn ions between V‐O interlayer further expands the layer spacing and increases the concentration of oxygen defects(Od),which boosts the Zn^(2+) diffusion kinetics.As a result,as‐prepared Cu_(0.17)Mn_(0.03)V_(2)O_(5−□)·2.16H_(2)O cathode shows outstanding Zn‐storage capabilities under room‐and lowtemperature environments(e.g.,440.3 mAh g^(−1) at room temperature and 294.3 mAh g^(−1)at−60°C).Importantly,it shows a long cycling life and high capacity retention of 93.4%over 2500 cycles at 2 A g^(−1) at−60°C.Furthermore,the reversible intercalation chemistry mechanisms during discharging/charging processes were revealed via operando X‐ray powder diffraction and ex situ Raman characterizations.The strategy of a couple of 3d transition metal doping provides a solution for the development of superior room‐/lowtemperature vanadium‐based cathode materials.

Sulfide-Based All-Solid-State Lithium-Sulfur Batteries:Challenges and Perspectives

Lithium-sulfur batteries with liquid electrolytes have been obstructed by severe shuttle effects and intrinsic safety concerns.Introducing inorganic solid-state electrolytes into lithium-sulfur systems is believed as an effective approach to eliminate these issues without sacrificing the high-energy density,which determines sulfidebased all-solid-state lithium-sulfur batteries.However,the lack of design principles for high-performance composite sulfur cathodes limits their further application.The sulfur cathode regulation should take several factors including the intrinsic insulation of sulfur,well-designed conductive networks,integrated sulfur-electrolyte interfaces,and porous structure for volume expansion,and the correlation between these factors into account.Here,we summarize the challenges of regulating composite sulfur cathodes with respect to ionic/electronic diffusions and put forward the corresponding solutions for obtaining stable positive electrodes.In the last section,we also outlook the future research pathways of architecture sulfur cathode to guide the develop high-performance all-solid-state lithium-sulfur batteries.

Beads-on-string hierarchical structured electrocatalysts for efficient oxygen reduction reaction

Rational design of hierarchically structured electrocatalysts is particularly important for electrocatalytic oxygen reduction reaction(ORR).Here,ZIF-67 crystals are stringed on core-shell Ag@C nanocables using a coordinationmodulated process.Upon pyrolysis,Ag@C strings of Co nanoparticles embedded with three-dimensional porous carbon with beads-on-string hierarchical structures are developed.Due to the advantages of the rich electrochemical active sites of Co-based“beads”and the efficient electron transfer pathways via Ag@C“strings,”the resultant NH_(3)-Ag@C@Co-N-C-700 catalyst shows an improved electrocatalytic activity toward ORR.NH_(3)-Ag@C@Co-N-C-700 shows a high onset potential of 0.99 V versus RHE,a high half-wave potential of 0.88 V versus RHE,and a large limiting current of 5.8 mA cm^(-2),which are better than those of commercial Pt/C electrocatalysts.Additionally,the NH_(3)-Ag@C@Co-N-C-700 catalyst shows high stability and preeminent methanol tolerance,which makes NH_(3)-Ag@C@Co-N-C-700 a promising catalyst for oxygen electrocatalysis in fuel cell applications.

Core-shell Prussian blue analogues derived from metal-organic frameworks as efficient electrocatalysts for oxygen evolution reaction

Developing high-performance and low-cost electrocatalysts for oxygen evolution reaction(OER)is still a great challenge for water-splitting technologies.Herein,an innovative metal-organic frameworks(MOFs)hybrid-assisted strategy is reported to synthesize core-shell Co/Mn-ZIF@Fe-Co-Mn Prussian blue analogues(PBAs)toward highly efficient OER electrocatalysts in alkaline electrolyte.Physical characterization indicates that the amorphous hydroxide transformed from Co/Mn-ZIF@Fe-Co-Mn PBA(ZIF:zeolitic imidazolate frameworks)during the electrochemical process acted as the electroactive species.Benefiting from these structural and compositional features,the developed composite delivers a remarkably low overpotential of 270 mV with a current density of 10 mA·cm^(−2)in 1.0 M KOH solution.Moreover,water splitting is catalyzed to reach a current density of 10 mA·cm^(−2)at 1.62 V.

Optimizing oxygen redox kinetics of M-N-C electrocatalysts via an in-situ self-sacrifice template etching strategy

The accessibility and mass transfer between catalytic sites and substrates/intermediates are essential to a catalyst's overall performance in oxygen electrocatalysis based energy devices.Here,we present an“in-situ self-sacrifice template etching strategy”for reconstructing MOF-derived M-N-C catalysts,which introduces micro-meso-macro pores with continuous apertures in a wide range and a central hollowout structure to optimize the electrochemical oxygen redox kinetics.It is realized via one-step pyrolysis of ZIF-8 single crystal epitaxially coating on a multi-functional template of the Fe,Co co-loaded mesoporous ZnO sphere.The ZnO core is reduced during the general pyrolysis of ZIF-8 into M-N-C and acts as a pore former to etch the surrounding ZIF-8 shell into diverse channels anchoring highly exposed Fe and Co-based active sites with edge enrichment.The redesigned catalyst reveals apparent structural benefits towards enhanced oxygen redox kinetics as bifunctional cathode catalysts of rechargeable zinc-air battery compared with the primitive bulk M-N-C catalysts and the mixture of commercial Pt/C and Ir/C.The unique structure-based activity advantages,the omitted template removal step and good template compatibility during synthesis make the strategy universal for the channel engineering of electrocatalysts.

Copper‑Based Catalysts for Electrochemical Carbon Dioxide Reduction to Multicarbon Products

Electrochemical conversion of carbon dioxide into fuel and chemicals with added value represents an appealing approach to reduce the greenhouse effect and realize a carbon-neutral cycle,which has great potential in mitigating global warming and effectively storing renewable energy.The electrochemical CO_(2) reduction reaction(CO_(2)RR)usually involves multiproton coupling and multielectron transfer in aqueous electrolytes to form multicarbon products(C_(2+) products),but it competes with the hydrogen evolution reaction(HER),which results in intrinsically sluggish kinetics and a complex reaction mechanism and places higher requirements on the design of catalysts.In this review,the advantages of electrochemical CO_(2) reduction are briefly introduced,and then,different categories of Cu-based catalysts,including monometallic Cu catalysts,bimetallic catalysts,metal-organic frameworks(MOFs)along with MOF-derived catalysts and other catalysts,are summarized in terms of their synthesis method and conversion of CO_(2) to C2+products in aqueous solution.The catalytic mechanisms of these catalysts are subsequently discussed for rational design of more efficient catalysts.In response to the mechanisms,several material strategies to enhance the catalytic behaviors are proposed,including surface facet engineering,interface engineering,utilization of strong metal-support interactions and surface modification.Based on the above strategies,challenges and prospects are proposed for the future development of CO_(2)RR catalysts for industrial applications.

Reviving zinc-air batteries with high-density metal particles on carbon

As a century-old technique,rechargeable zinc-air batteries have been rejuvenated in the past decade[1,2].Their aqueous electrolytes enable high ionic conductivity,safety operation and fast reaction kinetics for high-rate outputs.However,the popularization of Zn-air batteries is still struggling due to their insufficient performance.