Electron modulation of cobalt carbonate hydroxide by Mo doping for urea-assisted hydrogen production

Combining urea oxidation reaction(UOR) with hydrogen evolution reaction(HER) is an effective method for energy saving and highly efficient electrocatalytic hydrogen production. Herein, molybdenumincorporated cobalt carbonate hydroxide nanoarrays(CoxMoyCH) are designed and synthesized as a bifunctional catalyst towards UOR and HER. Benefiting from the Mo doping, the dispersed nanoarray structure and redistributed electron density, the CoxMoyCH catalyst display outstanding catalytic performance and durability for both HER and UOR, affording the overpotential of 82 m V for HER and delivering a low potential of the 1.33 V for UOR(vs. reversible hydrogen electrode, RHE) to attain a current density of 10 m A cm^(-2), respectively. Remarkably, when CoxMoyCH was applied as bifunctional catalyst in a twoelectrode electrolyzer, a working voltage of 1.40 V is needed in urea-assisted water electrolysis at10 m A cm^(-2) and without apparent decline for 40 h, outperforming the working voltage of 1.51 V in conventional water electrolysis.

Effect of La_2O_3 nanoparticles on properties of molybdenum powder

The properties of La 2O 3 doped molybdenum powder were studied. The La 2O 3 nanoparticles on the surface of molybdenum powder which is produced by the reduction of La(NO 3) 3 doped MoO 2 in hydrogen decrease the intensity of feature energy loss peak of molybdenum substrate; but increase that of peak of Mo?3d. The surface of molybdenum powder exposed to the atmosphere can be reduced because the surface is mainly covered with La 2O 3 nanoparticles. As a result, the capability of anti oxidation of molybdenum is improved.

A highly active and stable Sr_(2)Fe_(1.5)Mo(0.5)O_(6)‑δ‑Ce_(0.8)Sm_(0.2)O_(1.95)ceramic fuel electrode for efficient hydrogen production via a steam electrolyzer without safe gas

High temperature steam(H_(2)O)electrolysis via a solid oxide electrolysis cell is an efficient way to produce hydrogen(H_(2))because of its high energy conversion efficiency as well as simple and green process,especially when the electrolysis process is combined with integrated gasification fuel cell technology or derived by renewable energy.However,about 60%-70%of the electricity input is consumed to overcome the large oxygen potential gradient but not for electrolysis to split H_(2)O to produce H_(2)due to the addition of safe gas such as H_(2)in the fuel electrode.In this work,Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)-δ-Ce_(0.8)Sm_(0.2)O_(1.95)(SFM-SDC)ceramic composite material has been developed as fuel electrode to avoid the use of safe gas,and the open circuit voltage(OCV)has been effectively lowered from 1030 to 78 mV when the feeding gas in the fuel electrode is shifted from 3%H_(2)O-97%H_(2)to 3%H_(2)O-97%N_(2),reasonably resulting in a significantly increased electrolysis efficiency.In addition,it is also demonstrated that the electrolysis current density is greatly enhanced by increasing the humidity in the fuel electrode and the working temperature.A considerable electrolysis current density of−0.54 A/cm^(2)is obtained at 800°C and 0.4 V for the symmetrical electrolyzer by exposing SFM-SDC fuel electrode to 23%H_(2)O-77%N_(2),and durability test at 800°C for 35 h demonstrates a relatively stable electrochemical performance for steam electrolysis under the same operation condition without safe gas and a constant electrolysis current density of−0.060 A/cm2.Our findings achieved in this work indicate that SFM-SDC is a highly promising fuel electrode for steam electrolysis.

Polysulfides adsorption and catalysis dual-sites on metal-doped molybdenum oxide nanoclusters for Li-S batteries with wide operating temperature

The development of electrocatalysts with high catalytic activity is conducive to enhancing polysulfides adsorption and reducing activation energy of polysulfides conversion, which can effectively reduce polysulfide shuttling in Li-S batteries. Herein, a novel catalyst NiCo-MoO x /rGO (rGO = reduced graphene oxides) with ultra-nanometer scale and high dispersity is derived from the Anderson-type polyoxometalate precursors, which are electrostatically assembled on the multilayer rGO. The catalyst material possesses dual active sites, in which Ni-doped MoO x exhibits strong polysulfide anchoring ability, while Co-doped MoO x facilitates the polysulfides conversion reaction kinetics, thus breaking the Sabatier effect in the conventional electrocatalytic process. In addition, the prepared NiCo-MoO x /rGO modified PP separator (NiCo-MoO x /rGO@PP) can serve as a physical barrier to further inhibit the polysulfide shuttling effect and realize the rapid Li+ migration. The results demonstrate that Li-S coin cell with NiCo-MoO x /rGO@PP separator shows excellent cycling performance with the discharge capacity of 680 mAh·g^(−1) after 600 cycles at 1 C and the capacity fading of 0.064% per cycle. The rate performance is also impressive with the remained capacity of 640 mAh·g^(−1) after 200 cycles even at 4 C. When the sulfur loading is 4.0 mg·cm^(−2) and electrolyte volume/sulfur mass ratio (E/S) ratio is 6.0 μL·mg^(−1), a specific capacity of 830 mAh·g^(−1) is achieved after 200 cycles with a capacity decay of 0.049% per cycle. More importantly, the cell with NiCo-MoO x /rGO@PP separator exhibits cycling performance under wide operating temperature with the reversible capacities of 518, 715, and 915 mAh·g^(−1) after 100 cycles at −20, 0, and 60 °C, respectively. This study provides a new design approach of highly efficient catalysts for sulfur conversion reaction in Li-S batteries.

Mo-doped one-dimensional needle-like Ni_(3)S_(2) as bifunctional electrocatalyst for efficient alkaline hydrogen evolution and overall-water-splitting

Hydrogen energy plays an important role in clean energy system and is considered the core energy source for future technological development owing to its lightweight nature,high calorific value,and clean combustion products.The electrocatalytic conversion of water into hydrogen is considered a highly promising method.An electrocatalyst is indispensable in the electrocatalytic process,and finding an efficient electrocatalyst is essential.However,the current commercial electrocatalysts(such as Pt/C and Ru)are expensive;therefore,there is a need to find an inexpensive and efficient electrocatalyst with high stability,corrosion resistance,and high electrocatalytic efficiency.In this study,we developed a cost-effective bifunctional electrocatalyst by incorporating molybdenum into nickel sulfide(Ni_(3)S_(2))and subsequently tailoring its structure to achieve a one-dimensional(1D)needle-like configuration.The hydrogen production efficiency of nickel sulfide was improved by changing the ratio of Mo doping.By analyzing the electrochemical performance of different Mo-doped catalysts,we found that the Ni_(3)S_(2)-Mo-0.1 electrocatalyst exhibited the best electrocatalytic effect in 1 M KOH;at a current density of 10 mA cm^(-2),it exhibited overpotentials of 120 and 279 mV for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),respectively;at a higher current density of 100 mA cm^(-2),the HER and OER overpotentials were 396 and 495 mV,respectively.Furthermore,this electrocatalyst can be used in a two-electrode water-splitting system.Finally,we thoroughly investigated the mechanism of the overall water splitting of this electrocatalyst,providing valuable insights for future hydrogen production via overall-water-splitting.

Preparation of Quaternary FeCoMoCu Metal Oxides for Oxygen Evolution Reaction

Molybdenum doping is an effective way to improve the oxygen evolution reaction(OER)properties of catalysts,which can efficiently improve the electronic conductivity,mass transport process,and intrinsic activity of transition metal oxides or hydroxides,especially for those multi-component oxides with more abundant active sites.Herein,we have prepared a quaternary FeCoMoCu metal oxide on Cu foam(FeCoMoCuO_(x)@Cu)as an efficient OER catalyst.As expected,FeCoMoCuO_(x)@Cu could exhibit a low overpotential(252 mV at the current density of 10 mA/cm^(2))and exceptional stability(10000 cycles of CV scans or constant electrolysis for 48 h).

Carbon polyhedra encapsulated Si derived from Co-Mo bimetal MOFs as anode materials for lithium-ion batteries

Silicon(Si)holds promise as an anode material for lithium-ion batteries(LIBs)as it is widely avail-able and characterized by high specific capacity and suitable working potential.However,the relatively low electrical conductivity of Si and the significantly high extent of volume expansion realized dur-ing lithiation hinder its practical application.We prepared N-doped carbon polyhedral micro cage en-capsulated Si nanoparticles derived from Co-Mo bimetal metal-organic framework(MOFs)(denoted as Si/CoMo@NCP)and explored their lithium storage performance as anode materials to address these prob-lems.The Si/CoMo@NCP anode exhibited a high reversible lithium storage capacity(1013 mAh g^(−1)at 0.5 A g^(−1)after 100 cycles),stable cycle performance(745 mAh g^(−1)at 1 A g^(−1)after 400 cycles),and excellent rate performance(723 mAh g^(−1)at 2 A g^(−1)).Also,the constructed the full-cell NCM 811//Si/CoMo@NCP exhibited well reversible capacity.The excellent electrochemical performances of Si/CoMo@NCP were at-tributed to two unique properties.The encapsulation of NCP with doped nitrogen and porous structural carbon improves the electrical conductivity and cycling stability of the molecules.The introductions of metallic cobalt and its oxides help to improve the rate capability and lithiation capacity of the materials following multi-electron reaction mechanisms.