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Graphical abstract ZnO/CdS/PbS nanotube arrays with multi-heterojunctions were synthesized for efficient visible-light-driven photoelectrochemical hydrogen evolution. Highlights • Top-opened ZnO/CdS/PbS nanotube arrays film with multi-heterojunction is prepared. • The film exhibits remarkable visible-light photocatalytic activity and good stability. • The top-opened nanotube structure enhances light absorption and specific surface area. • Matched band energy edge of the multi-heterojunction enhance e−-h+ pair separation. Abstract High performance, low cost and sustainable photocatalytic evolution of hydrogen is a promising energy supply alternative for modern society to resolve the depletion crisis of fossil fuel. The design of multi-heterojunction visible-light photocatalysts combined with electrochemical means is considered one of the most attractive options in recent years. In this work, a photoanode composed of top-opened ZnO/CdS/PbS nanotube arrays (ZnO/CdS/PbS ONTs) with multi-heterojunctions was synthesized via a three-step process, i.e. hydrothermal treatment, chemical bath deposition and successive ionic layer adsorption reaction (SILAR). This as-prepared photoanode exhibited remarkable photoelectrochemical activity under visible light irradiation. The photocurrent density and photoelectrochemical hydrogen evolution efficiency of the optimized ZnO/CdS/PbS ONTs reached up to 14.2 mA cm−2 and 5.5 mL cm−2 h−1 at 0.0 V vs. Ag/AgCl, respectively. The efficiency was 3.1 times that of top-closed ZnO/CdS nanotubes (1.8 mL cm−2 h−1). The experimental results suggest that the high photoelectrochemical activity can be ascribed to the inherent advantages of the structural and successive energy level relays design: on the one hand, the top-opened nanotube structure significantly enlarges surface area of the nanostructure, which facilitates efficient light absorption and rapid mass transport; on the other hand, the well-matched band energy edge of the multi-heterojunction interfaces literally build efficient electron highways to deliver electrons to reaction sites and reduce the recombination of photogenerated charge carriers. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A facile one-pot carbonizing process is used to synthesize Fe 3 C nanocomposite. • Fe 3 C nanoparticles is embedded in nitrogen-doped porous carbon sheets. • Polysulfides is confined by strong Fe-S chemical bonds. • Conductive Fe3C facilitate fast electrochemical reactions. • The resultant Li-S battery deliver high performance and stability. Abstract The practical application of Li-S batteries is inherently limited by the low conductivity of sulfur and the dissolution of polysulfides. The enhancement of conductivity and introduction of polarity to the sulfur host is an effective strategy to overcome these long-standing challenges. In this work, a facile one-step carbonizing process is used to synthesize a unique porous and conductive nanocomposite where Fe 3 C nanoparticles are embedded in nitrogen-doped porous carbon sheets (Fe 3 C@NPCS). As demonstrated in Li 2 S 4 adsorption experiments and confirmed by density functional theory calculations, Fe 3 C nanoparticles are able to strongly adsorb polysulfides via strong Fe-S chemical bonds. Due to the remarkable conductivity, Fe 3 C nanoparticles can also accelerate the electrochemical reactions of the polysulfides through fast electron transportation. The carbon sheets prevent the aggregation of Fe 3 C nanoparticles and accommodate sulfur and its volume expansion during charge/discharge processes. With these features, the resultant sulfur cathodes (Fe 3 C@NPCS-S) deliver an excellent cycling performance with a capacity decay of 0.036% per cycle, and high rate performance of ca. 1127, 1020, 907, 802, 731 and 647 mAh g−1 under current densities of 0.3, 0.5, 1, 2, 3 and 5 C, respectively. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) have been considered as a promising cost-effective alternative for grid energy storage for renewable energy sources such as wind- and solar power. In this work, a bismuth nano-spheres and porous carbon composite (Bi-NS@C) is developed via an oleate-oriented dual-phase interfacial reaction and a molten salt calcination process. Materials characterizations suggest that the Bi-NS with a size of 20–30 nm are uniformly distributed in the sponge-like porous carbon network. Such a structure could enable a conductive network, prevent particle aggregation, shorten the ions transportation pathways, accommodate volume change and prevent the collapse of the electrode. As a result, this anode delivers a reversible discharge capacity of 106 mAh g −1 after even 1000 cycles at 0.2 A g −1 . Even at 2 A g −1 , the specific capacity of the electrode can still retain at ∼110 mAh g −1 . The remarkable electrochemical performance of the Bi-NS@C composite suggests that the as-prepared nanocomposite can simultaneously enhance the Na + ion conductivity and electronic conductivity in the charge/discharge processes, which offer guidance in anode materials design and synthesis in SIBs. [ABSTRACT FROM AUTHOR]

Abstract: This study compares the photocatalytic (PC) and photoelectrocatalytic (PEC) oxidation of glucose by Pt–TiO2 films under similar conditions. The overall oxidation efficiency of the PEC process was better than the PC process, for both TiO2 and Pt–TiO2 films. The Pt deposits enhanced the PEC oxidation efficiency of glucose at low cathodic (−0.1V) and low anodic potential bias (+0.1V). As the applied anodic bias was increased to >+0.5V, the undoped-TiO2 films outperformed their Pt–TiO2 counterparts. This suggests that in the studied systems, at an anodic bias of >+0.5V, more holes were available for the oxidation of glucose on the surface of TiO2 compared to Pt–TiO2 films. In the PEC systems, above a certain applied bias, Pt deposits may have a detrimental effect on the performance of a PEC system because the Pt deposits could merely block the surface of TiO2 (particularly at the highest Pt loadings). Lower measured photocurrents from Pt–TiO2 films compared to undoped-TiO2 and a decrease in the photocurrent as the Pt loading increased corroborate this postulation. [Copyright &y& Elsevier]

• TiO 2 -based photoelectrocatalysis (PEC) for chemical engineering and sensing. • PEC cell design facilicates maximum energy conversion efficicency. • Materials manipulation and bandgap engineering of TiO 2 to maximum light absorption. • PEC cell designs of small scale for sensing. • PEC cell designs of large scale for chemical engineering. Photoelectrocatalysis (PEC) incorporates electrochemical techniques with photocatalysis (PC) to facilitate the separation of the photoelectron-hole produced at semiconductor nanoparticles, leading to enhanced photocatalytic efficiency for various applications. Due to its inherently low cost, non-toxicity and chemical stability, titanium dioxide (TiO 2) based PEC devices are considered the most promising system for chemical engineering such as pollution degradation and fuel generation, and PEC sensing. In an attempt to bridge fundamental research and practical applications in chemical engineering and sensing, we herein systematically review recent advances in these PEC systems of different scales. More importantly, we offer a series of rational strategies including cell design, application of electric field photoelectrode morphology manipulation and bandgap engineering to enhance the performance of TiO 2 -based PEC devices and accelerate the commercialization of the TiO 2 -based PEC technology in chemical engineering. [ABSTRACT FROM AUTHOR]