Mg-doped SrTaO_(2)N as a visible-light-driven H_(2)-evolution photocatalyst for accelerated Z-scheme overall water splitting

Perovskite SrTaO_(2)N is one of the most promising narrow-bandgap photocatalysts for Z-scheme overall water splitting.However,the formation of defect states during thermal nitridation severely hinders the separation of charges,resulting in poor photocatalytic activity.In the present study,we successfully synthesize SrTaO_(2)N photocatalyst with low density of defect states,uniform morphology and particle size by flux-assisted one-pot nitridation combined with Mg doping.Some important parameters,such as the size of unit cell,the content of nitrogen,and microstructure,prove the successful doping of Mg.The defect-related carrier recombination has been significantly reduced by Mg doping,which effectively promotes the charge separation.Moreover,Mg doping induces a change of the band edge,which makes proton reduction have a stronger driving force.After modifying with the core/shell-structured Pt/Cr_(2)O_(3)cocatalyst,the H_(2)evolution activity of the optimized SrTaO_(2)N:Mg is 10 times that of the undoped SrTaO_(2)N,with an impressive apparent quantum yield of 1.51%at 420 nm.By coupling with Au-FeCoO_(x)modified BiVO_(4)as an O_(2)-evolution photocatalyst and[Fe(CN)_(6)]_(3)−/[Fe(CN)_(6)]_(4)−as the redox couple,a redox-based Z-scheme overall water splitting system is successfully constructed with an apparent quantum yield of 1.36%at 420 nm.This work provides an alternative way to prepare oxynitride semiconductors with reduced defects to promote the conversion of solar energy.

Electron transfer kinetics in CdS/Pt heterojunction photocatalyst during water splitting

Noble metal cocatalysts have shown great potential in boosting the performance of CdS in photocatalytic water splitting.However,the mechanism and kinetics of electron transfer in noble-metal-decorated CdS during practical hydrogen evolution is not clearly elucidated.Herein,Pt-nanoparticle-decorated CdS nanorods(CdS/Pt)are utilized as the model system to analyze the electron transfer kinetics in CdS/Pt heterojunction.Through femtosecond transient absorption spectroscopy,three dominating exciton quenching pathways are observed and assigned to the trapping of photogenerated electrons at shallow states,recombination of free electrons and trapped holes,and radiative recombination of locally photogenerated electron-hole pairs.The introduction of Pt cocatalyst can release the electrons trapped at the shallow states and construct an ultrafast electron transfer tunnel at the CdS/Pt interface.When CdS/Pt is dispersed in acetonitrile,the lifetime and rate for interfacial electron transfer are respectively calculated to be~5.5 ps and~3.5×10^(10) s^(−1).The CdS/Pt is again dispersed in water to simulate photocatalytic water splitting.The lifetime of the interfacial electron transfer decreases to~5.1 ps and the electron transfer rate increases to~4.9×10^(10) s^(−1),confirming that Pt nanoparticles serve as the main active sites of hydrogen evolution.This work reveals the role of Pt cocatalysts in enhancing the photocatalytic performance of CdS from the perspective of electron transfer kinetics.

Photocatalytic water splitting kinetics of CMV model

The photocatalytic water splitting kinetics has been analyzed in this paper.The experimental data are taken from the published works and fitted with different theoretical models.From the results,we find that the photocatalytic kinetics of water splitting can be described by Capelas-Mainardi-Vaz(CMV)model very well.This suggests that the water splitting kinetics can be regarded as a fractional first-order kinetics of the chemical reaction.Also,we notice that photocatalytic water splitting is not always completely a monotone kinetics process.

Facile one-pot hydrothermal method to prepare Sn(Ⅱ) and N co-doped TiO_(2) photocatalyst for water splitting under visible light irradiation

In this paper,a visible light-responsive Sn^(2+)and N co-doped TiO_(2)photocatalyst was prepared by facile one-pot hydrothermal method.All as-prepared samples were characterized in detail by a series of characterization approaches.The results showed that the Sn^(2+)and N elements were co-doped into TiO_(2),while the catalyst still maintains anatase crystal structure and gets irregular little nanocluster in diameter of 9–10 nm with higher specific surface area.The absorption edge of Sn^(2+)and N co-doped TiO_(2)extends to the visible light region.Compared with Sn^(2+)-doped TiO_(2)and N-TiO_(2),the absorption edges have obvious red-shift of about 50 and 70 nm,respectively.The synergistic effect of O 2p-N 2p and O 2p-Sn 5s hybridization to form impurity levels is the main reason for the red-shift.The hydrogen production performance of the Sn^(2+)and N co-doping TiO_(2)(n(N)/n(Ti)=1)catalyst reached the maximum value of 0.37 mmol·h^(-1)·g^(-1)under visible light,which is higher than that of N-doped TiO_(2)and SnTiO_(2)-doped TiO_(2)singly.This result is due to the wider visible light region-responsive ability of Sn^(2+)and N codoped into TiO_(2).Furthermore,mild hydrothermal methods will not make the Sn^(2+)oxidized to Sn^(4+),which make the catalysts still maintain high photocatalytic performance.This work provides a simple and mild method for the preparation of dual-element co-doped TiO_(2)with high crystallinity,excellent performance and broad application prospects.

可见光响应光解水制氢的半导体光催化剂

研究开发可见光响应的光催化剂一直是光解水制氢的首要目标。近年来通过能带调控等手段实现光催化剂的可见光化被广泛研究,并取得了令人注目的进展。本文综述了通过能带调变实现可见光化的各种手段,包括TiO2掺杂特别是阴离子掺杂、能响应可见光的新型固溶体和单相光催化材料的开发以及Z-型反应系统的构筑,以及通过电子结构的分析阐述其可见光化的机理。

新型光解水制氢用半导体光催化材料的研究进展

综述了钛酸盐、钽酸盐和铌酸盐为主的层状钙钛矿型光催化材料,简述了层状钙钛矿型光催化剂光解水的机理,比较了各种层状钙钛矿型结构材料的催化活性,分析了影响活性的原因,并对层状钙钛矿型结构光催化材料的研究和应用提出了一些自己的观点。

TiO_2光催化氧化的研究进展

概述了TiO2光催化氧化降解水中有机污染物的原理.阐述了提高TiO2光催化氧化活性的一些途径.指出了TiO2光催化氧化的研究现状,如固定相光催化氧化的进展,纳米TiO2的制备、表征及应用,TiO2光催化氧化对处理有机污染物的作用以及TiO2光催化氧化的动力学研究,并指出了今后光催化氧化的研究方向与发展趋势.可以预见光催化氧化将成为新型有效的水处理手段.

表面反应在半导体光催化水分解过程中的重要性

利用光解水制氢将太阳能直接转化并储存为氢和氧的化学能是解决能源危机和环境污染的有效途径之一。光解水制氢过程中光生载流子在材料表面处发生的氧化还原反应尤为复杂,由于表面反应拥有较高的过电位以及缓慢的气体脱附速率而成为整个光解水过程中的速控步骤,因此得到了研究者的重点关注和研究。本文就催化剂表面反应过程调控的科学问题进行简要总结和展望。结合光催化水分解基本原理,(i)阐述了促进表面水分解反应速率的主要方法;(ii)介绍了表面助催化剂的作用和分类;(iii)讨论了材料表面态的钝化和保护层的包覆对表面水分解反应的影响。最后对光催化水分解表面反应研究的未来发展方向提出了若干设想。

助催化剂在光催化分解水中的应用

在光催化分解水获取H2的研究中,核心的研究工作不仅致力于开发高效的光催化剂,同时更多研究专注于筛选适宜的助催化剂提升光催化活性。通过在光催化剂表面担载助催化剂,光催化剂的分解水活性显著提高。助催化剂在光催化分解水中的应用越来越多,其研究重心逐步从单助催化剂担载过渡到双组分或多组分助催化剂共同担载。本文对助催化剂的作用机理、种类和应用作一个简要的综述,并对助催化剂的选择和前景做了展望。

等离激元效应促进的光催化分解水制氢

[目的]利用光催化分解水的方式直接将太阳能转化并存储为氢气的化学能,是发展清洁能源促进低碳经济的有效途径。文章围绕等离激元效应对光催化分解水制氢的促进机理进行综述,以推进其产业化应用。[方法]阐释了等离激元效应在光催化分解水反应过程中的微观机制,分析了等离激元粒子在增强太阳光的吸收能力、拓展吸收光谱的响应范围、促进光生电子空穴的分离、提升光生载流子的热力学能、以及提供光催化反应活性中心等方面发挥的重要作用。[结果]通过总结当前等离激元效应促进光催化分解水制氢的研究进展,浅析了目前存在的问题,并对该领域的未来发展趋势进行了展望。[结论]基于等离激元效应在太阳能生产燃料中的巨大应用潜力,不同学科背景的相关学者协同合作,对影响光催化剂效率和寿命的各项决定性因素积极研发攻关,将促进该技术领域获得重要突破。

MIL-101应用于光催化产氢的研究进展

MIL-101是一种具有高比表面积、高孔隙率的金属有机框架结构材料。其骨架结构在300℃以下不发生变化,在水、空气和有机溶剂中结构更稳定,克服了大多数MOFs材料水热稳定性差的缺点,使MIL-101改性过程不易坍塌。其独特的框架结构有利于负载和调控具有优异催化性能的金属纳米粒子或化合物,有利于光生电子传输,便于进行官能团修饰,使其在光催化领域具有较大的应用潜力。本文介绍了MIL-101的合成与设计方法,综述了MIL-101在光催化产氢应用中存在的问题和优化改性策略,并对其应用前景进行了展望。