Ambient Fast Synthesis of Superaerophobic/Superhydrophilic Electrode for Superior Electrocatalytic Water Oxidation

Developing cost-effective and facile methods to synthesize efficient and stable electrocatalysts for large-scale water splitting is highly desirable but remains a significant challenge.In this study,a facile ambient temperature synthesis of hierarchical nickel-iron(oxy)hydroxides nanosheets on iron foam(FF-FN)with both superhydrophilicity and superaerophobicity is reported.Specifically,the as-fabricated FF-FN electrode demonstrates extraordinary oxygen evolution reaction(OER)activity with an ultralow overpotential of 195 mV at 10 mA cm^(-2)and a small Tafel slope of 34 mV dec^(-1)in alkaline media.Further theoretical investigation indicates that the involved lattice oxygen in nickel-iron-based-oxyhydroxide during electrochemical self-reconstruction can significantly reduce the OER reaction overpotential via the dominated lattice oxygen mechanism.The rechargeable Zn-air battery assembled by directly using the as-prepared FF-FN as cathode displays remarkable cycling performance.It is believed that this work affords an economical approach to steer commercial Fe foam into robust electrocatalysts for sustainable energy conversion and storage systems.

Li-and Mg-based borohydrides for hydrogen storage and ionic conductor

LiBH_(4) and Mg(BH_(4))_(2) with high theoretical hydrogen mass capacity receive significant attentions for hy-drogen storage.Also,these compounds can be potentially applied as solid-state electrolytes with their high ionic conductivity.However,their applications are hindered by the poor kinetics and reversibility for hydrogen storage and low ionic conductivity at room temperature,respectively.To address these challenges,effective strategies towards engineering the hydrogen storage properties and the emerging solid-state electrolytes with improved performances have been summarized.The focuses are on the state-of-the-art developments of Li/Mg-based borohydrides with a parallel comparison of similar methods ap-plied in both hydrogen storage and solid-state electrolytes,particularly on the phase,structure,and thermal properties changes of Li/Mg-based borohydrides induced by milling,ion substitution,coordination,adding additives/catalysts,and hydrides.The similarities and differences between the strategies towards two kinds of applications are also discussed and prospected.The review will shed light on the future development of Li/Mg-based borohydrides for hydrogen storage and solid-state electrolytes.

Design of metal-organic frameworks for improving pseudo-solid-state magnesium-ion electrolytes:Open metal sites,isoreticular expansion,and framework topology

The design criteria for metal-organic frameworks(MOFs)have been established by evaluating the rela-tionship between their key characteristics and magnesium-ion conductivity based on three types of sec-ondary building blocks(Zn_(4)O(CO_(2))_(6):MOF-5 and MOF-177;Cu_(2)(CO_(2))4:MOF-199,MOF-143,MOF-14,and MOF-399;Cu_(2)O_(2)(CO_(2))2:Cu-MOF-74)to achieve pseudo-solid-state magnesium-ion conduction.We found that open-metal sites and channel layouts play a pivotal role in promoting magnesium-ion transport dy-namics at reduced activation energy,transforming MOF scaffolds into ionic-channel analogs.X-ray ab-sorption spectroscopy combined with Raman and Fourier-transform infrared spectroscopy predicted the chemical environment,solvents,and anions that occupied coordinatively unsaturated metal sites.The chemical compositions of electrolytes determined by^(1)H-NMR(nuclear magnetic resonance)and organic elemental analysis confirmed that isoreticular expansion increases the molar percentage of charge carri-ers,providing high conductivity.The current research systematically reveals the impacts of different MOF characteristics on ionic conduction performance,paving the way for the construction of a new class of fast and selective multivalent-ion pseudo-solid electrolytes.

Highly nitrogen and sulfur dual-doped carbon microspheres for supercapacitors

Heteroatom doping, especially dual-doped carbon materials have attracted much attention for the past few years, and have been regarded as one of the most efficient strategies to enhance the capacitance behavior of porous carbon materials. In this work, a facile two-step synthetic route was developed to fabricate nitrogen and sulfur co-doped carbon microsphere(NSCM) by using thiourea as dopant. The N/S doping content is controlled via varying the carbonization temperature. It has been proved that a suitable quantity of N and S groups could not only provide pseudo-capacitance but also promote the electron transfer for carbon materials, which ensures the further utilization of the exposed surfaces for charge storage. The optimized NSCM prepared at a carbonization temperature of 800 °C(NSCM-800) achieves a capacitance of 277.1 Fg^(-1)at a current density of 0.3 Ag^(-1)in 6.0 mol L^(-1)KOH electrolyte, which is71% higher than that of undoped carbon microsphere. Besides, NSCM-800 shows an excellent cycling stability, 98.2% of the initial capacitance is retained after 5,000 cycles at a current density of 3.0 Ag^(-1).

Ultrafine molybdenum carbide nanoparticles supported on nitrogen doped carbon nanosheets for hydrogen evolution reaction

Molybdenum carbides(Mo_xC)/nitrogen doped carbon nanosheets(NCS) composites are synthesized via simple mixing melamine and ammonia molybdate, followed by a high-temperature treatment. Metal carbide nanoparticles with ultra-small size(13nm) are uniformly supported on nitrogen doped carbon nanosheets. The hydrogen evolution reaction(HER) is investigated in both 0.5 mol/L H_2SO_4 and 1 mol/L KOH media. Mo_2C/NCS-10(melamine/ammonia molybdate weight ratio of 10:1) exhibits excellent performance with a low overpotential of 130 mV in 0.5 mol/L H_2SO_4 solution and 108 mVin 1mol/L KOH solution at the current density of 10 mA/cm^2. The better electrocatalytic activity could be ascribed to Ndoped carbon nanosheets, small particle size, mesoporous structure, and large specific surface area,which could provide the large electrochemical active surface area and facilitate mass transport.