Cu₂ZnSnS₄ (CZTS) nanocrystals, synthesized by a hot injection solution method, have been fabricated into thin films by dip-casting onto fluorine doped tin oxide (FTO) substrates. The photoresponse of the CZTS nanocrystal films was evaluated using absorbance measurements along with photoelectrochemical methods in aqueous electrolytes. Photoelectrochemical characterization revealed a p-type photoresponse when the films were illuminated in an aqueous Eu(3+) redox electrolyte. The effects of CZTS stoichiometry, film thickness, and low-temperature annealing on the photocurrents from front and back illumination suggest that the minority carrier diffusion and recombination at the back contact (via reaction of photogenerated holes with Eu(2+) produced from photoreduction by minority carriers) are the main loss mechanisms in the cell. Low-temperature annealing resulted in significant increases in the photocurrents for films made from both Zn-rich and stoichiometric CZTS nanocrystals.

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Metal organic frameworks (MOFs)‐derived porous carbon is proposed as a promising candidate to develop novel, tailorable structures as polysulfides immobilizers for lithium–sulfur batteries because of their high‐efficiency electron conductive networks, open ion channels, and abundant central ions that can store a large amount of sulfur and trap the easily soluble polysulfides. However, most central ions in MOFs‐derived carbon framework are encapsulated in the carbon matrix so that their exposures as active sites to adsorb polysulfides are limited. To resolve this issue, highly dispersed TiO2 nanoparticles are anchored into the cobalt‐containing carbon polyhedras that are converted from ZIF‐67. Such a type of TiO2 and Co nanoparticles‐decorated carbon polyhedras (CCo/TiO2) provide more exposed active sites and much stronger chemical trapping for polysulfides, hence improving the sulfur utilization and enhancing reaction kinetics of sulfur‐containing cathode simultaneously. The sulfur‐containing carbon polyhedras decorated with TiO2 nanoparticles (S@CCo/TiO2) show a significantly improved cycling stability and rate capability, and deliver a discharge capacity of 32.9% higher than that of TiO2‐free S@CCo cathode at 837.5 mA g−1 after 200 cycles.

The lithium sulfur battery is regarded as a promising energy solution because of its high energy density. However, the insulating nature and large volumetric expansion of sulfur and the high solubility of polysulfides restrict their practical applications. Here carbon nanotube (CNT)-induced yolk−shell carbon nanopolyhedra, with Co−N-doping, is used as host material for sulfur. The CNTs are used to create a conductive network which interweaves each carbon polyhedron and induces the formation of a yolk−shell structure during the sulfur melt-diffusion process due to the "perforation effect". The CNT-connected Co−N-doped carbon nanopolyhedra containing sulfur yolk−shell structure (S@Co−N−C/CNTs-0.5) can achieve a capacity of 712.2 mAh g −1 at 1675 (1 C) mA g −1 after 300 cycles and 511.8 mAh g −1 at 3350 (2 C) mA g −1 . The outstanding performance is attributed to the new paradigm, S@Co−N−C/CNTs-0.5 yolk−shell structure, which creates a conductive network allowing for improved electron transport and convenient electrolyte infiltration, as well as enhanced reaction kinetics for the electrochemical process synchronously. The significant internal void space of yolk− shell structure effectively accommodates the volume expansion of sulfur. Simultaneously, Co−N-doping in yolk−shell structure carbon polyhedra can synergistically trap polysulfides due to the strong chemical adsorption.