The modulation of electron density is an effective option for efficient alternative electrocatalysts. Here, p‐n junctions are constructed in 3D free‐standing FeNi‐LDH/CoP/carbon cloth (CC) electrode (LDH=layered double hydroxide). The positively charged FeNi‐LDH in the space‐charge region can significantly boost oxygen evolution reaction. Therefore, the j at 1.485 V (vs. RHE) of FeNi‐LDH/CoP/CC achieves ca. 10‐fold and ca. 100‐fold increases compared to those of FeNi‐LDH/CC and CoP/CC, respectively. Density functional theory calculation reveals OH− has a stronger trend to adsorb on the surface of FeNi‐LDH side in the p‐n junction compared to individual FeNi‐LDH further verifying the synergistic effect in the p‐n junction. Additionally, it represents excellent activity toward water splitting. The utilization of heterojunctions would open up an entirely new possibility to purposefully regulate the electronic structure of active sites and promote their catalytic activities.

As an important material for many practical and research applications, porous silicon has attracted interest for decades. Conventional preparations suffer from high mass loss because of their etching nature. A few alternative routes have been reported, including magnesiothermic reduction; however, pre-formed porous precursors are still necessary, leading to complicated syntheses. Here we demonstrate a bottom-up synthesis of mesoporous crystalline silicon materials with high surface area and tunable primary particle/pore size via a self-templating pore formation process. The chemical synthesis utilizes salt by-products as internal self-forming templates that can be easily removed without any etchants. The advantages of these materials, such as their nanosized crystalline primary particles and high surface areas, enable increased photocatalytic hydrogen evolution rate and extended working life. These also make the mesoporous silicon a potential candidate for other applications, such as optoelectronics, drug delivery systems and even lithium-ion batteries.

Aqueous polysulfide/iodide redox flow batteries are attractive for scalable energy storage due to their high energy density and low cost. However, their energy efficiency and power density are usually limited by poor electrochemical kinetics of the redox reactions of polysulfide/iodide ions on graphite electrodes, which has become the main obstacle for their practical applications. Here, CoS 2 /CoS heterojunction nanoparticles with uneven charge distribution, which are synthesized in situ on graphite felt by a one-step solvothermal process, can significantly boost electrocatalytic activities of I − /I 3 − and S 2− /S x 2− redox reactions by improving absorptivity of charged ions and promoting charge transfer. The polysulfide/iodide flow battery with the graphene felt-CoS 2 /CoS heterojunction can deliver a high energy efficiency of 84.5% at a current density of 10 mA cm −2 , a power density of 86.2 mW cm −2 and a stable energy efficiency retention of 96% after approximately 1000 h of continuous operation.

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Ag2O/Bi2O2CO3 p-n heterojunctions are prepared with commercial Bi2O2CO3 as precursor via a simple photosynthesis process. The obtained Ag2O/Bi2O2CO3 p-n heterojunctions show higher photocatalytic activity than that of pure n-Bi2O2CO3, and the obtained Ag2O/Bi2O2CO3 (AB-4) heterojunction exhibits the best photocatalytic activity under visible light (λ > 400 nm), with which Rhodamine B, methyl blue and methyl orange can be completely degraded within 12 min. Photoluminescent spectra and photoelectrochemical measurement further indicate that the Ag2O/Bi2O2CO3 p-n heterojunctions greatly enhance the charge generation and suppress the charge recombination of photogenerated electron-hole pairs, which would be beneficial to improve their photocatalytic activity.

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