Ultrasound-induced Transition Metal Nitrides Splitting Water For Hydrogen Evolution

With the increasing energy crisis and environmental pollution,there is a growing worldwide desire for clean and renewable energy as an alternative to traditional fossil fuels.Hydrogen is considered a renewable energy source and one of the ideal substitutes for fossil fuels.Vibration energy is almost ubiquitous in our daily life,such as vibration,noise,etc.,it occurs almost anywhere.If all of this energy could be harvested and utilized,it would be an interesting and significant breakthrough in the energy field.Some catalytic materials have the potential to convert mechanical energy into chemical energy through the coupling of ultrasonic vibrations to electrochemical processes.So far,the hydrogen production performance of some traditional catalytic materials is not ideal.In recent years,transition metal nitrides（TMNs）have attracted much attention in the field of catalysis.TMNs generally exhibit good electrical conductivity and show promising applications in electrical,photo-or photoelectric catalytic reactions.It is a very practical approach to improve the piezoelectric properties of piezoelectric materials by constructing heterostructures.By constructing a heterostructure,charge carrier separation is facilitated,thereby enhancing sonocatalytic activity.The first work in this paper is to successfully synthesize a composite catalytic material of ternary transition metal nitride Ni₃FeN with oxide layer,and apply it to the model reaction of ultrasonic-assisted water splitting for hydrogen production;In the second work,the Co₄N-WN_x dual-phase transition metal nitride was successfully synthesized,and in pure water,it was used for ultrasonic-assisted water splitting to produce hydrogen.The oxygen-reactive species generated during the above two model reactions were deeply explored.The main research contents of this thesis are as follows:（1）The sample Ni₃FeN was obtained by the oxidation-rapid nitridation method,and the composite structure of the heterojunction of Ni₃FeN-Ni Fe O was further constructed by oxidation.The experimental results show that the composite material has relatively good hydrogen evolution performance.In order to explore the reaction mechanism,we carried out experiments such as electrochemical polarization curves and impedance tests on the samples.By adjusting the oxidation time,it was found that the composites oxidized for 10 min had the best hydrogen production.（2）Phase engineering between centrosymmetric Co₄N and non-centrosymmetric WN_xpromotes the charge carriers separation of Co₄N-WN_x.This piezoelectric property has been proven by piezoelectricforce microscopy（PFM）measurement.By modulating non-centrosymmetric structure of Co₄N-WN_x,the optimal sample exhibits hydrogen production rate about 262.7μmol g^-1 h^-1 in pure water.The results show that the material’s catalytic hydrogen evolution efficiency under ultrasound-induced conditions is considerable.In addition,Co₄N-WN_x can simultaneously achieve hydrogen production and Rh B degradation.This work provides a novel avenue for designing efficient ultrasonic catalytic materials.