Preparation And Photocatalytic Water-splitting Into Hydrogen Properties Of Ru/Co Synergetically Modified Ta₃N₅-based Nanophotocatalysts

Solar photocatalytic overall water-splitting into hydrogen has been considered as a effective ways to solve the issues including global energy and environmental crisis.Ta₃N₅ has a band gap of 2.1eV,and good response to visible light.It can efficiently use solar photolysis to splitting water into hydrogen.Theoretically,solar-to-hydrogen efficiency can reach 15.9%.Its photocatalytic efficiency is still far from the targeted solar energy efficiency of 5%using photocatalysis or photoelectrocatalysis because of the intrinsic drawbacks such as the fast recombination of charge carriers and serious self-oxidation by photogenerated holes.So through Ru/Co synergetic modification to form multiple heterostructures,and build a multifunctional surface interface heterostructure that targets HER and OER cocatalysts.It can synergetically promote light absorption,accelerate the separation and migration of photogenerated carriers,accelerate surface reactions to improve photocatalytic activity through multiple interfaces.Using Ta₃N₅@Ta₂O₅ as a precursor,investigated the preparation technology of Ru³⁺in-situ doping,immersion adsorption,and photodeposition modification Ta₃N₅@Ta₂O_5.Compared Ru³⁺-Co²⁺/Co³⁺synergetically modified Ta₃N₅@Ta₂O₅ in the preparation technology of modification amount and method.Futhermore,investigated RuO₂ and Co_xN_y synergetical modification process of Ta₂N/Ta₃N₅.The results showed that the photocurrent of photodeposition 0.6wt%5h Ru³⁺modified Ta₃N₅@Ta₂O₅ was 3times of the Ta₃N₅@Ta₂O₅ precursor.The photocurrent of photodeposition 0.6 wt%5 h Ru³⁺adsorption 3 wt%3 h Co²⁺/Co³⁺modification Ta₃N₅@Ta₂O₅ followed nitriding at800°C for 1 h was 34 times of the Ta₃N₅@Ta₂O₅ precursor.Using cubic Ta₃N₅@Ta₂O₅as a precursor,the photocurrent of photodeposition 0.6 wt%5 h Ru³⁺dipping adsorption3 wt%3 h Co²⁺/Co³⁺modification cubic Ta₃N₅@Ta₂O₅ was 3 times of the cubic Ta₃N₅@Ta₂O₅ precursor.Co_xN_y synergistically modified Ta₂N/Ta₃N₅ was prepared by adsorbing a 3 wt%Co³⁺-Ta₃N₅@Ta₂O₅ by nitriding at 1000°C for 1 h.Then RuO₂ and Co_xN_y synergistically modified Ta₂N/Ta₃N₅ were prepared by photodepositing 0.8 wt%Ru³⁺.Its photocurrent was 26 times of the Ta₃N₅@Ta₂O₅ precursor.It is confirmed that Ru/Co co-modification has a synergistic effect,which can effectively increase the photocurrent of the Ta₃N₅@Ta₂O₅ precursor.Accelerate the interface migration of photogenerated carriers and reduce the recombination probability of photo-generated electrons and holes.Co_xN_y and hydrous RuO₂ were separately anchored on Ta₂N/Ta₃N₅ surfaces to construct difuntional multi-heterostructure nanosheets.Structural and compositional features of the heterostructures were modulated for better photocatalytic performance by Ru³⁺mofidication amount.Both Co_xN_y/Ta₂N and hydrous Ru O₂/Ta₂N significantly increased photocurrent densities,and decreased HER and OER overpotentials.More importantly,synergetic effects of Co_xN_y/Ta₂N/Ta₃N₅ and RuO₂/Ta₂N/Ta₃N₅ on charge carrier separation and transfer,and on decrease in the overpotential of HER and OER were produced.Subnitride Co_5.47N producing a similar plasmon effect,and sub-bandgap behavior from reduced Ta species and anion defect N-vacancies improved visible light absorption.Increased charge transfer resistance by Co_xN_y/Ta₂N interface in comparison to that of Ta₃N₅@Ta₂O₅ precursor,was significantly reduced by further constructing RuO₂/Ta₂N heterojunction.New Ru-O-Ta linkages at RuO₂/Ta₂N interfaces facilitate fast separation and transfer of charge carriers.Micropores also provided more photoactive sites.All above factors cooperatively led to enhanced visible-light photocatalytic H₂-evolution activity 83.64umol·g^-1·h^-1.This article provides a new way for the further development of new and highly efficient and stable Ta₃N₅-based photocatalytic materials for visible light photocatalytic water splitting hydrogen.