Surface-clean low-doped PdB/C as superior electrocatalysts toward ethanol oxidation in alkaline media

Developing highly active, low-cost and organic surfactants-free Pd-based catalysts for ethanol oxidation reaction（EOR） is now critically important for direct ethanol fuel cells. Herein, surface-clean low-doped PdB/C catalysts（typically ca. 1.5 at% of B） are successfully prepared in an aqueous condition without adding any organic surfactants. TEM characterization shows that as-prepared low-doped Pd B nanoparticles are evenly distributed on carbon support. Cyclic voltommagrams of as-prepared low-doped PdB/C in 0.5 M NaOH ＋ 1 M C2H5OH indicate that its onset oxidation potential of ethanol is ca. 80-120 mV more negative than that on commercial Pd/C. Meanwhile, the EOR mass activity of our home-made catalysts is up to 4018 m A·mg-1 Pd. Moreover, the durability on low-doped PdB/C catalysts is at most 2 times higher than that on commercial Pd/C. Geometric and electronic effects are adopted to understand the above mentioned enhancement of activity and durability. This work may provide a facile, low-cost and green strategy on preparing electrocatalysts toward EOR in alkaline media.

Synergetic effect of stannate with o-aminophenol on inhibiting H2 evolution of A1 anode in strong alkaline media

The performance of Al-alloy anode in 4 mol/L KOH with and without stannate and o-aminophenol at 25℃ and 55℃ was studied by hydrogen collection, potentiodynamic polarization and electrochemical impedance spectrum, o-aminophenol acts as a perfect inhibitor because of its adsorbability and forming chelate complex at its optimum concentration of 0.4 mol/L. Stannate enhances the inhibition of o-aminophenol and improves the activity of Al-alloy because of its reduction to tin. There is synergetic effect of stannate with o-aminophenol on the behavior of Al-alloy, and the inhibitive efficiency at 55℃ is better than that at 25 ℃.

Polymer Film Supported Bimetallic Au–Ag Catalysts for Electrocatalytic Oxidation of Ammonia Borane in Alkaline Media

Ammonia borane is widely used in most areas including fuel cell applications.The present paper describes electrochemical behavior of ammonia borane in alkaline media on the poly(p-aminophenol) film modified with Au and Ag bimetallic nanoparticles.The glassy carbon electrode was firstly covered with polymeric film electrochemically and then,Au,Ag,and Au–Ag nanoparticles were deposited on the polymeric film,respectively.The surface morphology and chemical composition of these electrodes were examined by scanning electron microscopy,transmission electron microscopy,electrochemical impedance spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.It was found that alloyed Au–Ag bimetallic nanoparticles are formed.Electrochemical measurements indicate that the developed electrode modified by Au–Ag bimetallic nanoparticles exhibit the highest electrocatalytic activity for ammonia borane oxidation in alkaline media.The rotating disk electrode voltammetry demonstrates that the developed electrode can catalyze almost six-electron oxidation pathway of ammonia borane.Our results may be attractive for anode materials of ammonia borane fuel cells under alkaline conditions.

An insight into the enhanced mechanism of Ru–MoO_(2)interfacial chemical bonding for hydrogen evolution reaction in alkaline media

An effective strategy was proposed to control the formation of the interfacial bonding between Ru and molybdenum oxide support to stabilize the Ru atoms with the aim to enhance the hydrogen evolution reaction(HER)activity of the resultant catalysts in alkaline medium.The different interfacial chemical bonds,including Ru–O,Ru–O–Mo,and mixed Ru–Mo/Ru–O–Mo,were prepared using an induced activation strategy by controlling the composition of reducing agents in the calcination process.And the regulation mechanism of the interfacial chemical bonds in molybdenum oxide supported Ru catalysts for optimizing HER activity was investigated by density functional theory(DFT)and experimental studies.We found that a controlled interfacial chemical Ru–O–Mo bonding in Ru-MoO_(2)/C manifests a 12-fold activity increase in catalyzing the hydrogen evolution reaction relative to the conventional metal/metal oxide catalyst(Ru-O-MoO_(2)/C).In a bifunctional effect,the interfacial chemical Ru-O-Mo sites promoted the dissociation of water and the production of hydrogen intermediates that were then adsorbed on the nearby Ru surfaces and recombined into molecular hydrogen.As compared,the nearby Ru surfaces in Ru–Mo bonding have weak adsorption capacity for the generation of these hydrogen intermediates,resulting in a 5-fold increase HER activity for Ru-Mo-MoO_(2)/C catalyst compared with Ru-O-MoO_(2)/C.

Conversion of bimetallic MOF to Ru-doped Cu electrocatalysts for efficient hydrogen evolution in alkaline media

The rational design and construction of inexpensive and highly active electrocatalysts for hydrogen evolution reaction(HER)is of great importance for water splitting.Herein,we develop a facile approach for preparation of porous carbon-confined Ru-doped Cu nanoparticles(denoted as Ru-Cu@C)by direct pyrolysis of the Ru-exchanged Cu-BTC metal–organic framework.When served as the electrocatalyst for HER,strikingly,the obtained Ru-Cu@C catalyst exhibits an ultralow overpotential(only 20 mV at 10 mA cm^(-2))with a small Tafel slope of 37 m V dec^(-1)in alkaline electrolyte.The excellent performance is comparable or even superior to that of commercial Pt/C catalyst.Density functional theory(DFT)calculations confirm that introducing Ru atoms into Cu nanocrystals can significantly alter the desorption of H_(2) to achieve a close-to-zero hydrogen adsorption energy and thereby boost the HER process.This strategy gives a fresh impetus to explore low-cost and high-performance catalysts for HER in alkaline media.

CoFe-LDH nanowire arrays on graphite felt: A high-performance oxygen evolution electrocatalyst in alkaline media

Developing non-noble-metal oxygen evolution reaction(OER) electrocatalysts with high performance is critical to electrocatalytic water splitting. In this work, we fabricated Co Fe-layered double hydroxide(LDH) nanowire arrays on graphite felt(Co Fe-LDH/GF) via a hydrothermal method. The Co Fe-LDH/GF, as a robust integrated 3 D OER anode, exhibits excellent catalytic activity with the need of low overpotential of 252 and 285 mV to drive current densities of 10 and 100 mA/cm^(2) in 1.0 mol/L KOH, respectively. In addition, it also maintains electrochemical durability for at least 24 h. This work would open up avenues for the development of GF like attractive catalyst supports for oxygen evolution applications.

Alloying cobalt with ruthenium in nitrogen doped graphene layers for developing highly active hydrogen evolution electrocatalysts in alkaline media

Subject Code:B01With the support by the National Natural Science Foundation of China,a creative study by the research group led by Prof.Chen Qianwang(陈乾旺)from the University of Science and Technology of China and High Magnetic Field Laboratory,Hefei Institutes of Physical Science,Chinese Academy of

NiCoP nanoleaves array for electrocatalytic alkaline H2 evolution and overall water splitting

The development of non-precious, high-efficient and durable electrocatalysts for H2 evolution in alkaline media is highly desirable. Herein we report NiCoP nanoleaves array vertically grown on Ni foam for H2 evolution and overall water splitting via simple hydrothermal treatment and phosphorization. The selfsupported NiCoP nanoleaves architecture contributes to more exposed active sites, the smaller contact resistance between catalyst and substrate, faster ion diffusion and electron transfer. As a result, the optimized electrode requires only overpotentials of 98 and 173 mV to achieve current densities of 10 and100 m A cm-2 in 1.0 M KOH,respectively. Besides, used as both anode and cathode simultaneously, the electrode delivers current densities of 100 and 200 m A cm-2 at cell voltages of only 1.8 and 1.87 V, respectively. Moreover, the relatively high efficiency of about 11.4% for solar-driven water splitting further illustrates the application of our catalyst to sustainable development based on green technologies.

Electro-oxidation of mixed reactants of ethanol and formate on Pd/C in alkaline fuel cells

Direct ethanol fuel cells have attracted attention as an alternative energy technology due to several advantages such as high theoretical energy density and abundant supply of ethanol.In spite of the advantages,commercialization of direct ethanol fuel cells is hampered by the relatively low performance caused by its slow oxidation kinetics and difficulty of complete oxidation.In this study,formate,which has relatively faster oxidation kinetics,was mixed with ethanol to compensate the latter’s sluggish kinetics.Effects of p H,concentration,scan rate,and temperature on the mixed reactants oxidation on Pd were investigated by electrochemical experiments such as potential sweep and potentiostatic methods.Furthermore,the potential of the mixed reactants as fuel was evaluated by single cell experiments.As a result,we demonstrate that mixing formate with ethanol results in enhanced power performance in a single cell system.

Optimistic performance of carbon-free hydrazine fuel cells based on controlled electrode structure and water management

In this study, we first attempted to discover the optimal configuration of membrane-electrode assemblies(MEAs) used to achieve a high performance of direct hydrazine fuel cells(DHFCs). We have investigated the effect of water management and the electrode thickness on the performance of DHFCs, depending on the hydrophobicity of the gas diffusion layers in the cathode and the catalyst loading in the anode with the carbon-supported Ni, synthesized by a polyol process. With the optimal water management and electrode thickness, the MEA constructed using the as-prepared Ni/C anode catalyst containing the metallic and low oxidative state and ultra-low Pt loading cathode reduced the ohmic resistance and mass transfer limitation in the current-voltage curves observed for the alkaline DHFC, achieving an impressive power performance over 500 mW cm^(–2).

Co/N-doped carbon nanotube arrays grown on 2D MOFs-derived matrix for boosting the oxygen reduction reaction in alkaline and acidic media

The development of high-performance and cost-effective electrocatalysts towards oxygen reduction reaction(ORR) is of significant importance,but still challenging for the practical applications in related energy systems.ORR process typically suffers from sluggish kinetics,the exploration of ORR electrocatalyst thus requires elaborate design.Herein,an effective strategy is developed for growing Co/N-doped carbon nanotube arrays on 2D MOFs-derived matrix via the pyrolysis of Co/Zn metalorganic-framework(MOF) nanosheets.The Co/Zn-MOF nanosheets serve as both the self-template for the 2D carbonized framework morphology and C/N source for the in-situ growth of 1D N-doped carbon nanotubes.The constructed hie rarchical architecture effectively integrates the OD/1D Co nanoparticle/Ndoped carbon nanotube interface and 1D(nanotubes)/2D(nanosheets) junction into frameworks with highly exposed active surface,enhanced mass-transport kinetics and electrical conductivity.As a result,the designed composite exhibits superior ORR activity and durability in alkaline media as compared to commercial Pt/C.Particularly,it shows promising ORR performance with a half-wave potential of 0.78 V versus reversible hydrogen electrode and negligible activity attenuation after 5000 potential cycles in acidic electrolyte.The designed strategy can be extended to construct other MOFs-derived carbon matrixes with diverse hierarchical structures and provide an efficient avenue for searching highperformance electrocatalysts.

Phosphating-induced charge transfer on CoO/CoP interface for alkaline H_(2)evolution

Designing non-noble metal electrocatalysts toward alkaline hydrogen evolution reaction(HER)with high performance at a large current density is urgent.Herein,a CoO/CoP heterostructure catalyst(termed POZ)was designed by a phosphating strategy.The strong electron transfer on the interface of CoO/CoP was experimentally and theoretically proven.POZ showed a low overpotential of 236 mV at 400 mA/cm^(2),which was 249 mV lower than non-phosphated sample.It also exhibited a remarkable solar-to-hydrogen conversion efficiency of 10.5%.In this work,the construction of CoO/CoP interface realized by a simple phosphating strategy could provide an important reference to boost the HER performance on those materials not merely metal oxides.

Cobalt tungsten phosphide with tunable W-doping as highly efficient electrocatalysts for hydrogen evolution reaction

It has been of interest in seeking electrocatalysts that could exercise equally high-efficient and durable hydrogen evolution upon nonselective electrolytes in both acidic and alkaline environments. Herein, we report a facile strategy to fabricate cobalt tungsten phosphides (CoxW2−xP2/C) hollow polyhedrons with tunable composition based on metal-organic frameworks (MOFs) template method. By the deliberate control of W doping, the synthesized catalyst with the composition of Co0.9W1.1P2/C is found to be able to achieve a current density of 10 mA·cm^(−2) at overpotentials of 35 and 54 mV in acidic and alkaline media, respectively. This combined electrochemical property stands atop the state-of-the-art electrocatalyst counterparts. To unveil the peculiar behavior of the structure, density functional theory (DFT) calculation was implemented and reveals that the surface W-doping facilitates the optimization of hydrogen absorption free energy (ΔGH*) as well as the thermodynamic and kinetics barriers for water dissociation, which is coupled with the hollow structure of Co-W phosphides, leading to the prominent HER catalytic performance.

Facile NiCo_(2)S_(4)/C nanocomposite: an efficient material for water oxidation

The water oxidation in alkaline media is a kinetically sluggish process and it requires an active electrocatalyst for overall water splitting which is a challenging task to date.Herein,we formulate a platform for the design of efficient NiCo_(2)S_(4)/C nanocomposite using earth abundant and nonprecious materials.The nanocomposites are prepared by scale up hydrothermal method using different carbon contents from acid dehydrated sucrose.They are structurally and morphologically character-ized by various analytic techniques.The scanning electron microscopy has shown few microns flower-like morphology of nanocomposite and hexagonal crystalline phase is identified by X-ray diffraction(XRD).Further,high-resolution transmission electron microscopy supported the XRD results,and C,Ni,Co and O elements were found in the composition nanocomposite as investigated by energy-dispersive spectroscopy.The most active nanocomposite reaches a current density of 20 mA·cm^(−2) at potential of 285 mV vs reversible hydrogen electrode.The nanocomposite is kinetically supported by 61 mV·dec^(−1) as small Tafel slope.The nanocomposite is stable and durable for 40 h.The electrochemical impedance spectroscopy described a small charge transfer resistance of 188.4Ω.These findings suggest that the NiCo_(2)S_(4)/C nanocomposite could be used as a promising material for an extended range of applications particularly in energy technology.