Designing and synthesizing a highly active single atom catalyst, especially monodispersed noble-metal atoms fixed in two-dimensional layered double hydroxide (LDH) nanostructures, is crucial in accelerating the slow oxygen evolution reaction (OER). Here, Ru single atoms (SAs) are stabilized on NiFe LDH (SARu/NiFe LDH) via an oxygen-coordinated bond after a facile solution reduction procedure. The OER activity evaluation at similar mass loading on glassy carbon reveals that SARu/NiFe LDH shows more activity than pure NiFe LDH in basic media, possessing 99.3% of Faradaic efficiency based on rotating ring-disk electrode measurement. This is mainly due to a strong synergy between Ru SAs and NiFe LDH support. Furthermore, these supported catalysts are developed to an integrative 3D electrode in situ of the nickel foam with a higher specific surface area, which needs only an ultralow overpotential of 196 mV at 10 mA cm–2. This is one of the most efficient electrode containing monoatomic components to date. Theoretical calculations suggests that active sites of Ru can facilitate the rearrangement of electrons and optimize the binding energy both SARu/NiFe LDH catalyst and intermediates during the OER, thereby improving the intrinsic OER activity. This study provides a general avenue to developing efficiently monoatomic and even multiatomic catalysts in the future.

No abstract

The interfacial interaction in the In2S3@Bi2S3 vdW heterostructure is beneficial for transferring photogenerated holes to the surface with efficient water oxidation.

Improving the intrinsic catalytic activity of NiFe layered double hydroxide (LDH), which is a benchmark electrocatalyst for oxygen evolution reaction (OER), is a significant challenge. In the present study, we doped ruthenium ions into NiFe LDH (Ru-NiFe LDH) to accelerate the OER kinetics. Electrochemical measurements of NiFe LDH and Ru-NiFe LDH at similar mass loadings showed that Ru-NiFe LDH demonstrated a higher OER activity than that of NiFe LDH. Ru-NiFe LDH only requires an overpotential of 246 mV at 10 mA cm-2 in alkaline media. This is attributed to ruthenium doping primarily, which can promote the catalytic activity of Fe sites and boost the electronic interaction among the Ni, Fe, and Ru metals according to the theoretical calculations. Ru-NiFe LDH is stable during OER stability measurements, which was confirmed by structure and elemental analysis. These findings will provide a useful approach for promoting the intrinsic activity of multi-metallic (oxy) hydroxide electrocatalysts toward the OER.

No abstract

The development of efficient and stable non-noble-metal electrocatalytic materials for the oxygen evolution reaction (OER) is a huge and important challenge at present.

Aqueous asymmetric supercapacitors (ASCs) with a wide voltage window can effectively improve energy storage capacity of energy storage devices. Zeolitic imidazolate framework-67 (ZIF-67) was used as a precursor to prepare nanoporous carbon (NC), and K Mn O nanosheets were subsequently grown on the NC surface through a facile in situ redox process (denoted as NCMO). The electrode potential window of NCMO was extended to 1.2 V in a three-electrode system and the value of the potential window was higher than that of most reported manganese oxides. To assemble the asymmetric supercapacitor with a high voltage range, the as-prepared NCMO and NC (with a potential window of -1.2-0 V) were used as the positive and negative electrode, respectively. A 2.4 V NCMO//NC aqueous ASC was constructed and displayed a large energy density of 60 Wh kg at a power density of 1200 W kg and excellent rate performance (41 Wh kg even at a specific power density of 12.3 kW kg ) as well as good cycling stability (92.6 % capacitance retention over 10 000 cycles at 10 A g ). This work provides new opportunities for the development of high voltage ASCs with a high energy density for further practical application.

Hematite (Fe2O3) can be suitable when used in a solar energy conversion system, but the short charge diffusion lengths limit its applications. Here, we report the studies of charge transfer ability with a 40 nm Fe2O3 nanorod decorated by a 5 nm iron phosphide (FeP) core–shell structure. By selecting the optimized time of phosphorization (20 min), the photocurrent of FeP@Fe2O3-20 photoanode reached 0.86 mA/cm2, enhanced by 4.10-fold compared with pristine Fe2O3 (0.21 mA/cm2) for water oxidation. Further, the charge transport time reduced by 30% due to the FeP shell that served as the hole transport layer. Compared with Fe2O3, FeP@Fe2O3 has a higher Fermi level, which guides the electron’s transfer from FeP to Fe2O3 to create a space charge layer. The charge balance induces an upward bending of band structure at the FeP and Fe2O3 interface and accelerates the separation of photogenerated electron–holes ascribed to the built-in electric field at the interface. Our studies provide a detailed understanding of carrier dynamics in the core–shell structure, demonstrating a new route to explore high efficiency approaches for solar harvesting.