As low-cost electrocatalysts for oxygen reduction reaction applied to fuel cells and metal-air batteries, atomic-dispersed transition metal-nitrogen-carbon materials are emerging, but the genuine mechanism thereof is still arguable. Herein, by rational design and synthesis of dual-metal atomically dispersed Fe,Mn/N-C catalyst as model object, we unravel that the O2 reduction preferentially takes place on FeIII in the FeN4 /C system with intermediate spin state which possesses one eg electron (t2g4eg1) readily penetrating the antibonding π-orbital of oxygen. Both magnetic measurements and theoretical calculation reveal that the adjacent atomically dispersed Mn-N moieties can effectively activate the FeIII sites by both spin-state transition and electronic modulation, rendering the excellent ORR performances of Fe,Mn/N-C in both alkaline and acidic media (halfwave positionals are 0.928 V in 0.1 M KOH, and 0.804 V in 0.1 M HClO4), and good durability, which outperforms and has almost the same activity of commercial Pt/C, respectively. In addition, it presents a superior power density of 160.8 mW cm−2 and long-term durability in reversible zinc–air batteries. The work brings new insight into the oxygen reduction reaction process on the metal-nitrogen-carbon active sites, undoubtedly leading the exploration towards high effective low-cost non-precious catalysts.

The high-performance broadband photodetectors have attracted intensive scientific interests due to their potential applications in optoelectronic systems. Despite great achievements in two-dimensional (2D) materials based photodetectors such as graphene and black phosphorus, obvious disadvantages such as low optical absorbance and instability preclude their usage for the broadband photodetectors with the desired performance. An alternative approach is to find promising 2D materials and fabricate heterojunction structures for multifunctional hybrid photodetectors. In this work, 2D WS 2 /Si heterojunction with a type-II band alignment is formed in situ. This heterojunction device produced a high I on /I off ratio over 10, 6 responsivity of 224 mA/W, specific detectivity of 1.5 × 10 12 Jones, high polarization sensitivity, and broadband response up to 3043 nm. Furthermore, a 4 × 4 device array of WS 2 /Si heterojunction device is demonstrated with high stability and reproducibility. These results suggest that the WS 2 /Si type-II heterojunction is an ideal photodetector in broadband detection and integrated optoelectronic system.

A self-driven and broadband photodetector based on PdSe2/SiNWA mixed-dimensional vdW heterojunction is fabricated, which shows a broadband spectrum from 200 nm to 4.6 μm with a high polarization sensitivity and good mid-infrared imaging capability.

The rich variety and attractive properties of two-dimensional (2D) layered nanomaterials provide an ideal platform for fabricating next generation of advanced optoelectronic devices. Recently, a newly discovered 2D layered PtSe2 thin film has exhibited outstanding broadband sensitivity and optoelectronic properties. In our work, a large-area 2D layered PtSe2 thin film was used to construct the PtSe2/CdTe heterojunction infrared photodetector (PD). This PD exhibited a broad detection range coverage from 200 to 2000 nm with a high responsivity of 506.5 mA/W, a high specific detectivity of 4.2 × 1011 Jones, a high current on/off ratio of 7 × 106, and a fast response speed of 8.1/43.6 μs at room temperature. Additionally, the PtSe2/CdTe heterojunction PD exhibits excellent repeatability and stability in air. The high-performance of the PtSe2/CdTe heterojunction PD demonstrated in this work reveals that it has great potential to be used for broadband infrared detection.

High-performance self-powered solar-blind photodetector based on a MoS2/β-Ga2O3 heterojunction was demonstrated, which exhibits excellent solar-blind photoresponse properties.

Precise tuning of the chemical environment of neighboring atomic FeN 4 sites is extremely important for optimizing Fe−N−C catalysts to produce the fast oxygen reduction reaction (ORR) kinetics both in acidic and alkaline media, but it is actually very challenging. Heteroatoms could affect the metal charge of the active center through long-range electron delocalization; however, there are a few studies on it. Herein, density functional theory (DFT) calculations demonstrate that the addition of long-range P into edge-type FeN 4 can drive the electron delocalization and decrease the band gap of the FeN 4 center, leading to a substantial decrease in the free energy barrier to direct four-electron ORR kinetics compared to P-free edge-type FeN 4 , indicating superior intrinsic ORR activity. Experimentally, by incorporating P in edge-rich FeN 4 supported on N,P-doped carbon (Fe−N−C−P/N,P−C), the created Fe−N−C catalyst presents the greatly increased acidic ORR activity, with a half-wave potential (E 1/2 ) of 0.80 V (vs a reversible hydrogen electrode), which approaches that of commercial Pt/C and also has a high half-wave potential of 0.87 V, beyond Pt/C for alkaline ORR. In addition, it shows higher proton exchange membrane fuel cell and Zn-air battery performances than the pristine Fe−C−N catalyst (Fe−N−C/ N−C). This work will guide the rational design of highly active metal atomic scale catalysts with optimized chemical surroundings in terms of P incorporation as a chemically tunable method.

A high-performance self-powered photodetector based on a MoS2/GaAs heterojunction was demonstrated, which demonstrated a high responsivity, specific detectivity, fast response speeds, as well as high polarization sensitivity.

High-performance room-temperature infrared photodetectors based on MoS2/CdTe p–n heterojunction with broadband response, high responsivity, specific detectivity as well as fast response speed were demonstrated.