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.

Crystalline-amorphous interfaces of NiO-CrO_(x)electrocatalysts for boosting the urea oxidation reaction

The overall energy efficiency of electrochemical systems is severely hindered by the traditional anodic oxygen evolution reaction(OER).Utilizing urea oxidation reaction(UOR)with lower thermodynamic potential to replace OER provides a promising strategy to enhance the energy efficiency.Amorphous and heterojunctions electrocatalysts have been aroused extensive studies owing to their unique physicochemical properties and outperformed activity.Herein,we report a simple method to construct a novel crystalline-amorphous NiO-CrO_(x)heterojunction grown on Ni foam for UOR electrocatalyst.The NiO-CrO_(x)electrocatalyst displays excellent UOR performance with an ultralow working potential of 1.32 V at 10 mA·cm^(−2)and ultra-long stability about 5 days even at 100 mA·cm^(−2).In-situ Raman analysis and temperature-programmed desorption(TPD)measurement verify that the presence of the amorphous CrO_(x)phase can boost the reconstruction from NiO to active NiOOH species and enhance adsorption ability of urea molecule.Besides,the unique crystalline-amorphous interfaces are also benefit to improving the UOR performance.

多孔碳材料的研究进展

多孔碳材料具有高的比表面积、可调控的物理化学性质、价廉易得等优点,在能源存储和转换、催化、吸附分离等领域展现出了巨大的应用前景.多孔碳材料的制备方法和前驱体的选择直接决定了其性能及使用范围.聚合物结构丰富,通过碳化不同结构的聚合物制备多孔碳材料是目前多孔碳材料的研究热点之一.本文详细综述了目前多孔碳材料的主要制备方法以及聚合物作为碳前驱体,其结构与多孔碳材料结构与性能之间的构效关系.最后,对多孔碳材料的未来发展方向做了进一步的展望.

Ni_(2)P/NiMoP heterostructure as a bifunctional electrocatalyst for energy-saving hydrogen production

Electrochemical water splitting is a sustainable and feasible strategy for hydrogen production but is hampered by the sluggish anodic oxygen evolution reaction(OER).Herein,an effective approach is introduced to significantly decrease the cell voltage by replacing the anodic OER with a urea oxidation reaction(UOR).A Ni_(2)P/NiMoP nanosheet catalyst with a hierarchical architecture is uniformly grown on a nickel foam(NF)substrate through a simple hydrothermal and phosphorization method.The Ni_(2)P/NiMoP achieves impressive HER activity,with a low overpotential of only 22 mV at 10 mA cm^(-2)and a low Tafel slope of 34.5 mV dec^(−1).In addition,the oxidation voltage is significantly reduced from 1.49 V to 1.33 V after the introduction of 0.33 M urea.Notably,a two-electrode electrolyzer employing Ni_(2)P/NiMoP as a bifunctional catalyst exhibits a current density of 10 mA cm^(-2)at a cell voltage of 1.35 V and excellent long-term durability after 80 h.

Transition-Metal(Fe,Co,and Ni)-Based Nanofiber Electrocatalysts for Water Splitting

Electrochemical water splitting is a fascinating technology for sustainable hydrogen production,and electrocatalysts are essential to accelerate the sluggish hydrogen and oxygen evolution reactions(HER and OER).Transition-metal-based electrocatalysts have attracted enormous interests due to the abundant resources,low cost,and comparable catalytic performance to noble metals.Among these studies,fibrous materials possess distinct advantages,such as unique structure,high active surface area,and fast electron transport.Herein,the most recent progress of nanofiber electrocatalysts on synthesis and application in HER and OER is summarized,with emphasis on iron-,cobalt-,and nickel-based materials.Moreover,the challenge and prospects of fibrous-structured electrocatalysts on water splitting is provided.

N-doped ZrO_(2) nanoparticles embedded in a N-doped carbon matrix as a highly active and durable electrocatalyst for oxygen reduction

Fabricating highly efficient and robust oxygen reduction reaction(ORR)electrocatalysts is challenging but desirable for practical Zn-air batteries.As an early transition-metal oxide,zirconium dioxide(ZrO_(2))has emerged as an interesting catalyst owing to its unique characteristics of high stability,anti-toxicity,good catalytic activity,and small oxygen adsorption enthalpies.However,its intrinsically poor electrical conductivity makes it difficult to serve as an ORR electrocatalyst.Herein,we report ultrafine N-doped ZrO_(2) nanoparticles embedded in an N-doped porous carbon matrix as an ORR electrocatalyst(N-ZrO_(2)/NC).The N-ZrO_(2)/NC catalyst displays four-electron reduction of oxygen in O.1 M KOH,Upon employment in a Zn-air battery,N-ZrO,/NC presented an exellent activity and long-term durability with a half-wave potential(E,v2)of 0.84 V and a selectivity for the intriguing powerdensity of 185.9 mwcm^(-2).anda high secific capacity of 797.9 mA h gzni,exceeding those of commercial Pt/C(122.1 mw cm^(-2) and 782.5 mA h gzn),This excellent performance is mainly ttributed to the ultrafine ZrO_(2) nanoparticles the conductive carbon substrate,and the modifed electronic band structure of ZrO_(2) after N-doping.Density functional theory calculations demonstrated that N-doping can reduce the band-gap of ZrO_(2) from 3.96 eV to 3.33 eV through the hybridization of the p state of the N atom with the 2p state of the oxygen atom;this provides enhanced electrical conductivity and results in faster electron-transfer kinetics.This work provides a new approach for the design of other enhanced semiconductor and insulator materials.

PEM water electrolysis for hydrogen production:fundamentals,advances,and prospects

Hydrogen,as a clean energy carrier,is of great potential to be an alternative fuel in the future.Proton exchange membrane(PEM)water electrolysis is hailed as the most desired technology for high purity hydrogen production and self-consistent with volatility of renewable energies,has ignited much attention in the past decades based on the high current density,greater energy efficiency,small mass-volume characteristic,easy handling and maintenance.To date,substantial efforts have been devoted to the development of advanced electrocatalysts to improve electrolytic efficiency and reduce the cost of PEM electrolyser.In this review,we firstly compare the alkaline water electrolysis(AWE),solid oxide electrolysis(SOE),and PEM water electrolysis and highlight the advantages of PEM water electrolysis.Furthermore,we summarize the recent progress in PEM water electrolysis including hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)electrocatalysts in the acidic electrolyte.We also introduce other PEM cell components(including membrane electrode assembly,current collector,and bipolar plate).Finally,the current challenges and an outlook for the future development of PEM water electrolysis technology for application in future hydrogen production are provided.