MOF-derived Zn-Co-Ni sulfides with hollow nanosword arrays for high-efficiency overall water and urea electrolysis

Water electrolysis is a promising technology to produce hydrogen but it was severely restricted by the slow oxygen evolution reaction(OER).Herein,we firstly reported an advanced electrocatalyst of MOF-derived hollow Zn-Co-Ni sulfides(ZnS@Co_(9)S_(8)@Ni_(3)S_(2)-1/2,abbreviated as ZCNS-1/2)nanosword arrays(NSAs)with remarkable hydrogen evolution reaction(HER),OER and corresponding water electrolysis performance.To reach a current density of 10 mA cm^(-2),the cell voltage of assembled ZCNS-1/2//ZCNS-1/2 for urea electrolysis(1.314 V)is 208 mV lower than that for water electrolysis(1.522 V)and stably catalyzed for over 15 h,substantially outperforming the most reported water and urea electrolysis electrocatalysts.Density functional theory calculations and experimental result clearly reveal that the properties of large electrochemical active surface area(ECSA)caused by hollow NSAs and fast charge transfer resulted from the Co_(9)S_(8)@Ni_(3)S_(2) heterostructure endow the ZCNS-1/2 electrode with an enhanced electrocatalytic performance.

Hierarchical coral-like NiMoS nanohybrids as highly efficient bifunctional electrocatalysts for overall urea electrolysis

Novel hierarchical coral-like Ni-Mo sulfides on Ti mesh （denoted as HC-NiMoSfri） were synthesized through facile hydrothermal and subsequent sulfuration processes without any template. These non-precious HC-NiMoS/Ti hybrids were explored as bifunctional catalysts for urea-based overall water splitting, including the anodic urea oxygen evolution reaction （UOR） and cathodic hydrogen evolution reaction （HER）. Due to the highly exposed active sites, excellent charge transfer ability, and good synergistic effects from multi-component reactions, the HC-NiMoS/Ti hybrid exhibited superior activity and high stability, and only a cell voltage of 1.59 V was required to deliver 10 mA.cm-2 current density in an electrolyte of 1.0 M KOH with 0.5 M urea.

Controllable Ni/NiO interface engineering on N-doped carbon spheres for boosted alkaline water-to-hydrogen conversion by urea electrolysis

Interface engineering has gradually attracted substantial research interest in constructing active bifunctional catalysts toward urea electrolysis.The fundamental understanding of the crystallinity transition of the components on both sides of the interface is extremely significant for realizing controllable construction of catalysts through interface engineering,but it still remains a challenge.Herein,the Ni/NiO heterogenous nanoparticles are successfully fabricated on the porous N-doped carbon spheres by a facile hydrothermal and subsequent pyrolysis strategy.And for the first time we show the experimental observation that the Ni/NiO interface can be fine-tuned via simply tailoring the heating rate during pyrolysis process,in which the crystalline/amorphous or crystalline/crystalline Ni/NiO heterostructure is deliberately constructed on the porous N-doped carbon spheres(named as CA-Ni/NiO@NCS or CC-Ni/NiO@NCS,respectively).By taking advantage of the unique porous architecture and the synergistic effect between crystalline Ni and amorphous NiO,the well-designed CA-Ni/NiO@NCS displays more remarkable urea oxidation reaction(UOR)and hydrogen evolution reaction(HER)activity than its crystalline/crystalline counterpart of CC-Ni/NiO@NCS.Particularly,the whole assembled two-electrode electrolytic cell using the elaborate CANi/NiO@NCS both as the anode and cathode can realize the current density of 10 mA·cm^(−2)at a super low voltage of 1.475 V(264 mV less than that of pure water electrolysis),as well as remarkable prolonged stability over 63 h.Besides,the H_(2)evolution driven by an AA battery and a commercial solar cell is also studied to enlighten practical applications for the future.

Porous rod-like Ni_(2)P/Ni assemblies for enhanced urea electrooxidation

The urea oxidation reaction has attracted increasing attention.Here,porous rod-like Ni2P/Ni assemblies,which consist of numerous nanoparticle subunits with matching interfaces at the nanoscale have been synthesized via a simple phosphating approach.Density functional theory calculations and density of states indicate that porous rod-like Ni2P/Ni assemblies can significantly enhance the activity of chemical bonds and the conductivity compared with NiO/Ni toward the urea oxidation reaction.The optimal catalyst of Ni2P/Ni can deliver a low overpotential of 50 mV at 10 mA·cm−2 and Tafel slope of 87.6 mV·dec−1 in urea oxidation reaction.Moreover,the constructed electrolytic cell exhibits a current density of 10 mA·cm−2 at a cell voltage of 1.47 V and an outstanding durability in the two-electrode system.This work has provided a new possibility to fabricate metal phosphides-metal assemblies with advanced performance.