Study On Electrocatalysis Of Hydroxide(Oxide) In The Process Of Hydrogen Production By Water Splitting

With the development of society,the living standard of human beings has been greatly improved.In order to maintain a high standard of living,the human demand for energy is also increasing.After the industrial revolution,fossil fuels have brought great energy support to human beings.However,due to their limited amount and pollution caused by combustion,people have to develop alternative clean energy.Hydrogen energy has attracted people's attention and a lot of research because of its abundant,diverse,high calorific value,high utilization rate,non-pollution of combustion products.Among the existing hydrogen production technologies,electrolysis of water to produce hydrogen is the most efficient and sustainable method.As the process of hydrogen production by electrolysis of water consists of two electrode reactions,hydrogen evolution?HER?and oxygen evolution?OER?,the reaction process requires a high overpotential and consumes too much electric energy.In order to reduce the reaction overpotential,scientists need to make great efforts to design and synthesize electrocatalytic materials with high catalytic performance,low manufacturing cost and simple synthesis method.Platinum-based catalysts,ruthenium and iridium-based catalysts are widely recognized as the most efficient electrocatalytic materials for hydrogen and oxygen evolution reactions.However,due to its low content and high price,precious metals cannot be used in large-scale industry.Transition metal oxides and hydroxides have high catalytic performance and can work stably in alkaline environment.They are considered as alternative catalytic materials.In this work,Co₃O₄octahedral particles and nickel-iron bimetallic hydroxide were used as electrocatalysts,and their material characteristics,catalytic activity and stability for HER and OER were studied by various material characterization methods and electrochemical methods.1.By one-step hydrothermal method,NiFe layered double hydroxide?LDHs?was synthesized at 120 deg c and 240 deg c,respectively.The phase transition results in high catalytic activity of the two materials for oxygen evolution and hydrogen evolution,respectively.In alkaline medium,246 mV overpotential was applied at 100 mA/cm² for oxygen evolution reaction,and 93 mV overpotential is applied for a current density of 10 mA/cm² for hydrogen evolution reaction.Adopting the optimal conditions,?-NiFe-LDHs as the cathode and?-NiFe-LDHs as anode,it just need 1.52 V for a current density of 10 mA/cm² for overall water splitting and endured 20 hours of endurance testing.2.Octahedral Co₃O₄ particles were grown in situ on a foamed cobalt substrate by a simple one-step hydrothermal method.Co₃O₄ particles with a large number of{111}high index surface exposures and double layer capacitance of up to 154.85 mF/cm² were synthesized.Due to the absence of oxidants in the process of synthesis,the surface of the material is rich in a large number of oxygen vacancies and surface hydroxyl groups.The synergistic effect of several properties makes the material have efficient hydrogen evolution reaction and oxygen evolution reaction catalytic performance.In alkaline medium,when the current density is 10 mA/cm²,only77.9 mV overpotential needs to be applied for hydrogen evolution reaction;for oxygen evolution reaction process,only 301.2 mV overpotential needs to be added.For overall water splitting,only 1.60 V potential is needed to maintain the current density of 10 mA/cm².The 20-hour durability test shows that the material has high catalytic stability.