Cobalt-based Electrocatalysts Toward Glucose Oxidation Coupling With Alkaline Hydrogen Production

Hydrogen has been considered as an ideal energy carrier because of its advantages of the cleanness,abundant source,low-cost,high energy density and sustainability.Compared with the traditional steam reforming technology,hydrogen produced from electrochemical water splitting is a sustainable and green technology with alleviating the CO₂ emission.Unfortunately,the kinetically sluggish anodic oxygen evolution reaction（OER）in water splitting severely hinders the efficiency of hydrogen generation.Moreover,oxygen generated at the anode is not only useless but also hazardous when mixed with hydrogen.Therefore,it is particularly important to develope a new electrolytic hydrogen production system with low cost,low energy consumption,high efficiency and high safety.As a large agricultural country,our country is rich in biomass energy,and it is very promising to convert hydrogen energy through deepening processing.However,glucose,the most abundant biomass on the earth,is much lower in the theoretical oxidation potential（0.05V vs.RHE）than OER（1.23V vs.RHE）.It can also be selectively oxidized into various high-value chemical products.Formic acid is one of the basic organic chemical raw materials,which is widely used in pesticide,leather,dye,medicine and rubber industries.Therefore,replacing the OER with glucose oxidation reaction（GOR）at the anode offers a promising strategy for electrochemical hydrogen production,which can effectively reduce the energy consumption of electrolytic hydrogen production and realize glucose increment conversion.Co based catalysts have multiple advantages such as adjustable 3d electronic structure,low reaction initiation potential,high abundance in nature,and low price.Therefore,it is of great significance to design efficient and stable electrocatalysts and explore the mechanism of GOR reaction.The specific research contents are as follows:（1）A seires of MCo₂O₄（M=Cu,Co,Zn,Ni,Mn）spinel oxide catalyst was synthesized on nickel foam by hydrothermal and calcination.Cu Co₂O₄ catalyst has the best performance for glucose electrooxidation reaction（GOR）,in which the industrial current density of 500 m A cm^-2 can be reached only by 1.4 V vs.RHE,in agreement with the Faraday efficiency of formate up to 98%The Cu Co₂O₄ catalyst was retained more than 80 h for GOR at 1.35 V.Especially,when the Cu Co₂O₄ electrode were assembled into a two-electrode system in the precense of glucose,a quite low cell voltage of 1.59 V is needed to drive the electrolyzer at 200 m A cm^-2,which is 370 m V lower than that required by traditional water decomposition under the same conditions.Meanwhile,the Faraday efficiency of hydrogen production in this work have been closed to 100%.（2）Ni Co Se_x catalyst was synthesized in situ on nickel foam by hydrothermal and solvothermal method.The potential of as low as 1.32 and 1.41 V vs.RHE are required for the glucose oxidation at anode to reach a high catalytic current density of 200 and500 m A cm^-2,respectively.In-situ Raman spectra reveals that Co O_x/Co OOH and Ni OOH formed in situ on the surface of the Ni Co Se_x nanoplates electrode serves as active species to efficiently catalyze the electrooxidation of glucose.Ni Co Se_x has excellent GOR/HER dual-function electrocatalytic activity.The assembled electrolyzer only requires a voltage input of 1.5 V to achieve a current density of 200 m A cm^-2 by pairing GOR with hydrogen evolution reaction（HER）and retains long-term stability over 18 h.Compared with the traditional water decomposition device,the voltage is reduced by 390 m V and the hydrogen production is increased by 5.4 times.