Molybdenum-induced tuning 3d-orbital electron filling degree of CoSe_(2) for alkaline hydrogen and oxygen evolution reactions

The development of high-performance non-precious metal-based robust bifunctional electrocatalyst for both hydrogen evolution reaction(HER) and oxygen evolution reactions(OER) in alkaline media is essential for the electrochemical overall water splitting technologies. Herein, we demonstrate that the HER/OER performance of Co Se_(2)can be significantly enhanced by tuning the 3d-orbital electron filling degree through Mo doping. Both density functional theory(DFT) calculations and experimental results imply that the doping of Mo with higher proportion of the unoccupied d-orbital(P_(un)) could not only serve as the active center for water adsorption to enhance the water molecule activation, but also modulate the electronic structures of Co metal center leading to the optimized adsorption strength of*H. As expected, the obtained Mo-Co Se_(2)exhibits a remarkable bifunctional performance with overpotential of only 85 m V for HER and 245 m V for OER to achieve the current density of 10 m A/cm^(2)in alkaline media.This work will provide a valuable insight to design highly efficient bifunctional electrocatalyst towards HER and OER.

NiRh nanoparticles supported on nitrogen-doped porous carbon as highly efficient catalysts for dehydrogenation of hydrazine in alkaline solution

有在从 metalorganic 框架(ZIF-8 ) 导出的做氮的多孔的碳(NPC ) 上支持的不同作文的分散得好的二金属的 NiRh nanoparticles (NP ) 通过一个合作减小方法被综合。NPC-900 支持了 NiRh 催化剂展览向从肼的氢产生的最高催化的活动和 100% 氢选择。这些性质可能被归因于高表面区域和 NPC 的高 graphitization。这策略可以为由作为支持利用 NPC 抛锚设计高效的催化剂开创一条新大街为另外的应用的活跃金属 NP。

Nitrogen-doped graphene hydrogel-supported NiPt-CeOx nanocomposites and their superior catalysis for hydrogen generation from hydrazine at room temperature

The safe and efficient storage and release of hydrogen is one of the key technological challenges for the fuel cell-based hydrogen economy. Hydrazine monohydrate has attracted considerable attention as a safe and convent chemical hydrogen-storage material. Herein, we report the facile synthesis of NiPt-CeOx nanocomposites supported by three-dimensional nitrogen-doped graphene hydrogels （NGHs） via a simple one-step co-reduction synthesis method. These catalysts were composition-dependent for hydrogen generation from an alkaline solution of hydrazine. （NisPt5）I-（CeOx）0.B/NGH exhibited the highest catalytic activity, with 100% hydrogen selectivity and turnover frequencies of 408 h^-1 at 298 K and 3,064 h^-1 at 323 K. These superior catalytic performances are attributed to the electronic structure of the NiPt centers, which was modified by the electron interaction between NiPt and CeOx and the strong metal-support interaction between NiPt-CeOx and the NGH.

NiPt nanoparticles supported on CeO_2 nanospheres for efficient catalytic hydrogen generation from alkaline solution of hydrazine

Searching for highly efficient catalysts toward dehydrogenation of hydrazine for chemical hydrogen storage is highly desirable for the development of hydrogen economy. Herein, we report a simple in situ co-reduction synthesis of NiPt nanoparticles supported on CeO_2 nanospheres and their superior catalytic performance for hydrogen generation from alkaline solution of hydrazine at room temperature. Thanks to the strong electronic interaction arising from synergistic effect at atomic lever and support-metal interaction between NiPt and CeO_2.The obtained Ni_5Pt_5-CeO_2 catalyst exhibits 100% hydrogen selectivity and superior catalytic performance for hydrogen generation from alkaline solution of hydrazine at room temperature, with a TOF value of 416 h 1.

Three-dimensional nitrogen-doped graphene hydrogel supported Co-CeOx nanoclusters as efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

The development of highly active noble-metal-flee catalysts for catalytic hydrolysis of ammonia borane is mandatory for its application in hydrogen storage. Herein, Co-CeOx nanoclusters have been successfully anchored on a three-dimensional nitrogen-doped graphene hydrogel （NGH） by a simple coreduction method and further used as efficient catalysts to catalytic hydrolysis of ammonia borane at room temperature. Thanks to the strong synergistic electronic effect between Co and CeOx, as well as the strong metal-support interaction between Co-CeOx and 3D NGH, the as-synthesized Co-（CeOx）0.91/NGH catalyst exhibits superior catalytic activity toward hydrolysis of ammonia borane, with the turnover frequency （TOF） value of 79.5 min 1, which is almost 13 times higher than that of Co]NGH, and higher than most of the reported noble-metal-free catalysts.

Enhanced catalytic activity of Ru through N modification toward alkaline hydrogen electrocatalysis

Exploring highly efficient electrocatalysts and understanding the reaction mechanisms for hydrogen electrocatalysis,including hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in alkaline media are conducive to the conversion of hydrogen energy.Herein,we reported a new strategy to boost the HER/HOR performances of ruthenium (Ru) nanoparticles through nitrogen (N) modification.The obtained N-Ru/C exhibit remarkable catalytic performance,with normalized HOR exchange current density and mass activity of 0.56 m A/cm^(2)and 0.54 m A/μg,respectively,about 4 and 4.5 times higher than those of Ru/C,and even twofold enhancement compared to commercial Pt/C.Moreover,at the overpotential of 50 m V,the normalized HER current density of N-Ru/C is 5.5 times higher than that of Ru/C.Experimental and density functional theory (DFT) results verify the electronic regulation of Ru after N incorporation,resulting in the optimized hydrogen adsorption Gibbs free energy (ΔG_(H*)) and hence enhancing the HOR/HER performance.

A synergy establishment by metal-organic framework and carbon quantum dots to enhance electrochemical water oxidation

Available online Integrating transition metal centered MOFs with conductive materials is a feasible route to enhance electron transfer efficiency of materials.Herein,a composite porous structure CQDs_(10)@NiFe-MOF-A was fabricated via introducing carbon quantum dots(CQDs)into porous NiFe-MOF.The CQDs would make partial loss of lattice in MOF during its growth,leading to the composite building block with the coexistance of crystalline region and amorphous region.The calcining treatment would produce an ultrathin protective layer as well as some lattice collapse.The synergy effect between NiFe ions effectively regulated electronic structure of metal active sites,and successful grafting of CQDs to NiFe-MOF significantly improved electrical conductivity.As expected,the catalyst exhibited outstanding OER performances with high mass activity of 91.6 A/g at overpotential of 300 mV and robust durability of 10,000 cycles in 1 mol/L KOH,which outperformed that of noble catalyst IrO_(2)of 25.2 A/g.The strategy paves a feasible and effective avenue for the non-noble metal catalysts.

The Role of Hydroxide Binding Energy in Alkaline Hydrogen Oxidation Reaction Kinetics on RuCr Nanosheet

Unveiling the role of adsorbed hydroxide involved in the hydrogen oxidation reaction(HOR)under alkaline electrolyte is crucial for the development of advanced HOR electrocatalysts for the alkaline polymer electrolyte fuel cells(APEFCs).Herein,we report the synthesis of amorphous RuCr nanosheets with different molar ratios and their HOR performances under alkaline media.We find a volcano correlation between the Cr content in RuCr nanosheets and their alkaline HOR performance.Experimental results and density functional theory(DFT)calculation reveals that the optimized Cr content in RuCr nanosheets could lead to the optimum hydroxide binding energy(OHBE),contributes to their remarkable alkaline HOR performance with mass activity of 568.1 A·gPGM^(–1) at 50 mV,13-fold higher than that of Ru catalyst.When RuCr nanosheet is further used as the anodic electrocatalyst,a peak power density of 1.04 W·cm^(–2 )can be achieved in an APEFC.

3D mesoporous rose-like nickel-iron selenide microspheres as advanced electrocatalysts for the oxygen evolution reaction

The development of efficient and stable non-noble metal-based electrocatalysts for the oxygen evolution reaction （OER） is one of the essential challenges for the upcoming hydrogen economy. Herein, three-dimensional （3D） mesoporous nickel iron selenide with rose-like microsphere architecture was directly grown on Ni foam via a successive two-step hydrotherrnal method. The unique 3D mesoporous rose-like morphology leads to a higher number of active sites as well as fast mass and electron transport through the entire electrode, and facilitates the release of 02 bubbles formed during the OER catalysis. As a result, the synthesized Ni0.76Fe0.24Se exhibits superior OER performances, with an ultralow overpotential of 197 mV needed to produce a current density of 10 mA.cm-2 in 1 M KOH, outperforming all transition metal selenide OER catalysts reported to date.

Nickel-iron borate coated nickel-iron boride hybrid for highly stable and active oxygen evolution electrocatalysis

The development of efficient and cost-effective electrocatalysts toward anodic oxygen evolution reaction(OER) is crucial for the commercial application of electrochemical water splitting.As the most promising electrocatalysts,the OER performances of nickel-iron-based materials can be further improved by introducing metalloid elements to modify their electron structures.Herein,we developed an efficient hybrid electrocatalyst with nickel-iron boride(NiFeB) as core and amorphous nickel-iron borate(NiFeBi)as shell(NiFeB@NiFeBi) via a simple aqueous reduction.The obtained NiFeB@NiFeBi exhibits a small overpotential of 237 mV at 10 mA/cm^2 and Tafel slope of 57.65 mV/dec in 1.0 mol/L KOH,outperforming most of the documented precious-metal-free based electrocatalysts.Benefiting from the in situ formed amorphous NiFeBi layer,it shows excellent stability toward the oxygen evolution reaction(OER).These findings might provide a new way to design advanced precious-metal-free electrocatalysts for OER and the application of electrochemical water splitting.