NiFe-layered double hydroxides (NiFe-LDHs), as promising electrocatalysts, have received significant research attention for hydrogen and oxygen generation through water splitting. However, the slow oxidation kinetics of NiFe-LDH, due to the limited number of active sites and the low conductivity, hinders the improvement of the water-splitting efficiency. Therefore, to overcome the obstacles, two-dimensional (2D) SnS was first explored to tailor the prepared NiFe-LDH via the hydrothermal method. A NiFe-LDH/SnS heterojunction is built, which is observed from the microstructural investigations. SnS incorporation could greatly improve the conductivity of the NiFe-LDH sheets, which was reflected by the reduced charge transfer resistance. Moreover, SnS layers modulated the electronic environment around the active sites, favoring the adsorption of intermediates during the oxygen evolution reaction (OER) process, which was verified by density functional theory calculations. A synergistic effect induced by the NiFe-LDH/SnS heterostructure promoted the OER activities in electrical, electronic, and energetic aspects. Consequently, the as-prepared NiFe-LDH/SnS electrocatalyst greatly improved the electrocatalytic performance, exhibiting 20% and 27% reductions in the overpotential and Tafel slope compared with those of pristine NiFe-LDH, respectively. The results provide a strategy for regulating NiFe-based electrocatalysts by using emerging 2D materials to enhance water-splitting efficiency.

Bi₂Se₃ possesses a two-dimensional layered rhombohedral crystal structure, where the quintuple layers (QLs) are covalently bonded within the layers but weakly held together by van der Waals forces between the adjacent QLs. It is also pointed out that Bi₂Se₃ is a topological insulator, making it a promising candidate for a wide range of electronic and optoelectronic applications. In this study, we investigate the growth of high-quality Bi₂Se₃ thin films on mica by the molecular beam epitaxy technique. The films exhibited a layered structure and highly c-axis-preferred growth orientation with an XRD rocking curve full-width at half-maximum (FWHM) of 0.088°, clearly demonstrating excellent crystallinity for the Bi₂Se₃ deposited on the mica substrate. The growth mechanism was studied by using an interface model associated with the coincidence site lattice unit (CSLU) developed for van der Waals epitaxies. This high (001) texture favors electron transport in the material. Hall measurements revealed a mobility of 726 cm²/(Vs) at room temperature and up to 1469 cm²/(Vs) at 12 K. The results illustrate excellent electron mobility arising from the superior crystallinity of the films with significant implications for applications in conducting electrodes in optoelectronic devices on flexible substrates.

Photocatalytic degradation, as an emerging method to control environmental pollution, is considered one of the most promising environmental purification technologies. As Tibet is a region with some of the strongest solar radiation in China and even in the world, it is extremely rich in solar energy resources, which is ideal for applying photocatalytic technology to its ecological environment protection and governance. In this study, Na₂Ti₃O₇ nanobelts were prepared via a hydrothermal method and converted to TiO₂∙xH₂O ion exchange, which was followed by high-temperature calcination to prepare TiO₂(B) nanobelts (“B” in TiO₂(B) means “Bronze phase”). A simple in situ method was used to generate Ag₃PO₄ particles on the surface of the TiO₂ nanobelts to construct a Ag₃PO₄/TiO₂(B) heterojunction composite photocatalyst. By generating Ag₃PO₄ nanoparticles on the surface of the TiO₂(B) nanobelts to construct heterojunctions, the light absorption range of the photocatalyst was successfully extended from UV (ultraviolet) to the visible region. Furthermore, the recombination of photogenerated electron–hole pairs in the catalyst was inhibited by the construction of the heterojunctions, thus greatly enhancing its light quantum efficiency. Therefore, the prepared Ag₃PO₄/TiO₂(B) heterojunction composite photocatalyst greatly outperformed the TiO₂(B) nanobelt in terms of photocatalytic degradation.

Currently, precious metal group materials are known as the efficient and widely used oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts. The exorbitant prices and scarcity of the precious metals have stimulated scale exploration of alternative non-precious metal catalysts with low-cost and high performance. Layered double hydroxides (LDHs) are a promising precursor to prepare cost-effective and high-performance catalysts because they possess abundant micropores and nitrogen self-doping after pyrolysis, which can accelerate the electron transfer and serve as active sites for efficient OER. Herein, we developed a new highly active NiFeMn-layered double hydroxide (NFM LDH) based electrocatalyst for OER. Through building NFM hydroxide/oxyhydroxide heterojunction and incorporation of conductive graphene, the prepared NFM LDH-based electrocatalyst delivers a low overpotential of 338 mV at current density of 10 mA cm⁻² with a small Tafel slope of 67 mV dec⁻¹, which are superior to those of commercial RuO₂ catalyst for OER. The LDH/OOH heterojunction involves strong interfacial coupling, which modulates the local electronic environment and boosts the kinetics of charge transfer. In addition, the high valence Fe³⁺ and Mn³⁺ species formed after NaOH treatment provide more active sites and promote the Ni²⁺ to higher oxidation states during the O₂ evolution. Moreover, graphene contributes a lot to the reduction of charge transfer resistance. The combining effects have greatly enhanced the catalytic ability for OER, demonstrating that the synthesized NFM LDH/OOH heterojunction with graphene linkage can be practically applied as a high-performance electrocatalyst for oxygen production via water splitting.

Pollution remains one of the most significant global challenges. Photocatalysis consists of a new organic pollutant removal technology, with TiO₂ widely studied as a photocatalyst in the photocatalytic removal of water pollution. However, intrinsic TiO₂ has the disadvantages of weak visible light absorption, low electron separation, and transmission efficiency, as well as few active sites. In this study, anatase-phase Ti³⁺ self-doped TiO₂ (B-TiO₂) with a core-shell structure was successfully prepared by forming an amorphous layer rich in oxygen vacancies (OVs) and Ti³⁺ defects on the TiO₂ surface under a nitrogen atmosphere using NaBH₄ as a chemical-reducing agent. The visible light absorption performance of the catalyst was notably improved when exposed to light irradiation. The bending of surface energy bands facilitated the separation of photogenerated electron-hole pairs, and the core-shell structure allowed the electron-hole pairs to be transported to the surface of the catalyst and participate in the reaction faster. We observed that 92.86% of Rhodamine B (RhB) was degraded in only 5 min, an increase of 2.73 times that of the degradation rate observed in commercial P25. With extraordinary stability, the photocatalytic efficiency of the catalyst remained at 96.2% after five degradation cycles.