电化学制备异质二氧化钛结构增强其在光电分解水中转化效率（英文）

本文描述了一种利用电化学方法合成第二型异质二氧化钛纳米棒结构的方法,这种纳米棒由部分还原的黑色二氧化钛和原始的白色二氧化钛组成.这种异质结结构的半还原的二氧化钛纳米棒与原始的白色二氧化钛和完全还原的黑色二氧化钛纳米棒相比,展现出更好的光电催化性能.这可归结于这种条件下合成的纳米棒具备的协同作用.一方面,这类结构增强了整个太阳光光谱的利用率.底层的黑色二氧化钛能够大量吸收可见光,而上层的白色二氧化钛能够较好的利用太阳光中紫外光的部分.另一方面,因为形成了第二型异质结结构,电荷的激发分离和传输得到了有效的控制.这种简单的制备方法可进一步拓展合成其他金属氧化物,来进一步研究光电分解水的性能.本文利用传统的三电极系统:0.05 mol/L的硫酸作为电解液,在加–0.5 V的偏压下进行.相比与已报道的还原手段,该电解液中质子的浓度相对比较低,可以保证这个还原过程逐步发生.电化学还原曲线可以明显反映二氧化钛还原的过程,尽管从扫描电子显微镜中很难观察到响应的区别,但是在该过程中,电极片的颜色发生了明显的变化.相应的,我们将这个系列的电极进行了光学和晶体学的研究,发现其在还原过程中,能带能够逐步减小.而在X射线衍测试当中,仅最终完全还原的得到的样品在20度左右出现两个额外的峰,可归结为还原状态的二氧化钛.电化学扫描进一步测试其能带的相应位置,证明了黑色被还原的二氧化钛和白色的原始二氧化钛是同时存在的.最后将这个系列光电极光电催化分解水的性能进行了比较,发现在同等的测试条件下,形成异质结结构的二氧化钛具有最高的光催化效率,其值大约是白色二氧化钛的三倍,同时也比纯黑的二氧化钛增长了20%左右.另外,异质结结构的二氧化钛与黑色的相比,在可见光区域有相同的效率的同时具备更好的紫外光转化效率.最后,我们分析了异质结形成以后的相对应的能带结构,该结构能够更好的促进光吸收和转化.

Self-template synthesis of hollow Fe-doped CoP prisms with enhanced oxygen evolution reaction activity

The development of efficient, durable and low cost electrocatalysts is crucial but extremely challenging for the oxygen evolution reaction (OER). Herein, we develop a self-template strategy to synthesize hollow Fe-doped CoP prisms (Fe-CoP) via ion exchange of cobalt acetate hydroxide with [Fe(CN)_(6)]^(3-) and phosphorization-induced transformation of CoFe-PBA (Co/Fe-containing prussian blue analogue) prisms in N2 atmosphere. The obtained Fe-CoP not only inherits the hollow prism-like morphology of CoFe-PBA, but also forms rich mesoporous channel. The Fe-CoP prisms exhibit extraordinary OER performances in 1.0 M KOH, with a low overpotential of 236 mV to deliver a current density of 10 mA cm^(−2) and a low Tafel slope of 32.9 mV dec^(–1). Moreover, the presented electrocatalyst shows good long-term operating durability and activity. The XPS and TEM analysis confirm that Fe-CoP has undergone surface reconstruction in the process of electrocatalytic OER, and the in situ formed oxides and oxyhydroxides are the real active species to boost OER. This work provides a promising pathway to the design and synthesis of efficient and robust electrocatalysts with hierarchical hollow structure for boosting OER.

cPCN-Regulated SnO_(2) Composites Enables Perovskite Solar Cell with Efficiency Beyond 23%

Efficient electron transport layers(ETLs)not only play a crucial role in promoting carrier separation and electron extraction in perovskite solar cells(PSCs)but also significantly affect the process of nucleation and growth of the perovskite layer.Herein,crystalline polymeric carbon nitrides(cPCN)are introduced to regulate the electronic properties of SnO_(2) nanocrystals,resulting in cPCN-composited SnO_(2)(SnO_(2)-cPCN)ETLs with enhanced charge transport and perovs-kite layers with decreased grain boundaries.Firstly,SnO_(2)-cPCN ETLs show three times higher electron mobility than pristine SnO_(2) while offering better energy level alignment with the perovskite layer.The SnO_(2)-cPCN ETLs with decreased wettability endow the perovskite films with higher crystallinity by retarding the crystallization rate.In the end,the power conversion efficiency(PCE)of planar PSCs can be boosted to 23.17%with negligible hysteresis and a steady-state efficiency output of 21.98%,which is one of the highest PCEs for PSCs with modified SnO_(2) ETLs.SnO_(2)-cPCN based devices also showed higher stability than pristine SnO_(2),maintaining 88%of the initial PCE after 2000 h of storage in the ambient environment(with controlled RH of 30%±5%)without encapsulation.

S-scheme heterojunction of crystalline carbon nitride nanosheets and ultrafine WO_(3)nanoparticles for photocatalytic CO_(2)reduction

Highly crystalline carbon nitride polymers have shown great opportunities in overall water photosplitting;however,their mission in light-driven CO_(2)conversion remains to be explored.In this work,crystalline carbon nitride(CCN)nanosheets of poly triazine imide(PTI)embedded with melon domains are fabricated by KCl/LiCl-mediated polycondensation of dicyandiamide,the surface of which is subsequently deposited with ultrafine WO_(3)nanoparticles to construct the CCN/WO_(3)heterostructure with a S-scheme interface.Systematic characterizations have been conducted to reveal the compositions and structures of the S-scheme CCN/WO_(3)hybrid,featuring strengthened optical capture,enhanced CO_(2)adsorption and activation,attractive textural properties,as well as spatial separation and directed movement of light-triggered charge carriers.Under mild conditions,the CCN/WO_(3)catalyst with optimized composition displays a high photocatalytic activity for reducing CO_(2)to CO in a rate of 23.0μmol/hr(i.e.,2300μmol/(hr·g)),which is about 7-fold that of pristine CCN,along with a high CO selectivity of 90.6%against H2formation.Moreover,it also manifests high stability and fine reusability for the CO_(2)conversion reaction.The CO_(2)adsorption and conversion processes on the catalyst are monitored by in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS),identifying the crucial intermediates of CO_(2)^(*)-,COOH^(*)and CO^(*),which integrated with the results of performance evaluation proposes the possible CO_(2)reduction mechanism.

Photocatalytic oxidation of methane to methanol over zinc titanate supported silver catalysts

The direct activation of methane under mild condition to achieve highly selective of oxygenates is a challenging project.In this study,a well dispersed silver supported ZnTiO_(3) catalyst was prepared to achieve selective preparation of methanol from methane and water under mild condition.X-ray diffraction,transmission electron microscopy and X-ray photoelectron spectroscopy characterizations demonstrate that silver species are uniformly dispersed on ZnTiO_(3) surface in the form of metallic silver nanoparticles.The photoelectric characterizations reveal that the addition of silver species enhances light absorption and promotes charge separation of the catalysts.Under the reaction conditions of 50℃and 3 MPa,the methanol is obtained as the only liquid product over the designed Ag/ZnTiO_(3) catalyst under light irradiation.In this photocatalytic process,the holes generated by ZnTiO_(3) activate water to produce intermediate·OH,which further reacts with methane to synthesize methanol.The silver species as co-catalysts extend the light absorption range of ZnTiO_(3) as well as promote charge separation.

Photocatalysis:an overview of recent developments and technological advancements

Photocatalysis,which is the catalyzation of redox reactions via the use of energy obtained from light sources,is a topic that has garnered a lot of attention in recent years as a means of addressing the environmental and economic issues plaguing society today.Of particular interest are photosynthesis can potentially mimic a variety of vital reactions,many of which hold the key to develop sustainable energy economy.In light of this,many of the technological and procedural advancements that have recently occurred in the field are discussed in this review,namely those linked to:(1)photocatalysts made from metal oxides,nitride,and sulfides;(2)photocatalysis via polymeric carbon nitride(PCN);and(3)general advances and mechanistic insights related to TiO2-based catalysts.The challenges and opportunities that have arisen over the past few years are discussed in detail.Basic concepts and experimental procedures which could be useful for eventually overcoming the problems associated with photocatalysis are presented herein.

Roles of Metal-Free Materials in Photoelectrodes for Water Splitting

CONSPECTUS:Photoelectrochemical(PEC)water splitting is an appealing approach to the hydrogen evolution reaction since it converts sunlight in the form of hydrogen fuel,which has the potential to revolutionize the fossil fuel-based energy systems of the modern society.In the last half century,progress has been made with respect to the material,synthesis,and system.Recent developments of multilayered photoelectrodes have made a breakthrough to improve the sunlight conversion efficiency and strengthen the physiochemical stability.The exploration of new materials for the functional layers of photoelectrodes offers a new opportunity for practical application.Among the emerging materials,metal-free species have shown superior properties,such as high stability,sustainability,and renewability.With respect to inorganic materials,their physiochemical properties can be readily regulated,including thermodynamics and kinetics,and thus increasing attention has been devoted.