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Developing non-noble metal-based electrocatalyst with high catalytic activity is essential for advancing hydrogen energy technologies. This study introduces a hydrothermal method for synthesizing order Ni(OH)2 nanosheets, with H3O40PW12 (denoted as PW12) loaded onto reduced graphene oxide (rGO) coated on nickel foam (referred to as PW12-Ni(OH)2/rGO). This method contrasts with the electrodeposition of Ni(OH)2, where PW12 is added to the synthetic system to direct the assembly and morphology of the Ni(OH)2 through a hydrothermal reaction. In this work, the nickel foam acts dual roles as both the substrate and the source of nickel for the formation of Ni(OH)2. The PW12-Ni(OH)2/rGO nanosheets, when successfully prepared and loaded onto the nickel foam (NF), exhibited superior electrocatalytic activity for the hydrogen evolution reaction (HER) in an alkaline electrolyte, achieving a current density of 10 mA·cm−2 at an overpotential of 69 mV. Furthermore, we endeavored to expand the application of this material towards the oxygen evolution reaction (OER) by preparing PW12-(Fe/Co)Ni(OH)2/rGO through the addition of metal cations. This nanocomposite displayed outstanding electrocatalytic activity in alkaline electrolytes, with a current density of 10 mA·cm−2 at an overpotential of 211 mV, and demonstrated excellent stability over a 50 h period in a 1 M KOH solution. The results presented in this paper offer an effective strategy for the preparation of polyoxometalate-based inorganic materials with diverse functionalities, applicable to both HER and OER. [ABSTRACT FROM AUTHOR]

The slow light effect at the band gap edge of photonic nanocrystals (PhCs) can improve the light utilization efficiency of photocatalysts by enhancing light collection. This study reported an anatase inverse opal TiO2 (IO TiO2) with a 3D closely packed face-centered cubic structure prepared using a PhC template. The simulation of the electric field modulus distribution in the inverse opal structure was performed, and the enhancement of photocatalytic efficiency caused by the slow light effect at the red and blue edges of the photonic band gap was analyzed. The experimental results of rhodamine B degradation agreed with the simulation. IO TiO2 has a high specific surface area (91 m2/g), which is 4.33 times that of powder TiO2, and also has high pore volumes (0.13 cm3/g). In addition, it facilitates the separation of photogenerated carriers due to the existence of large pores that are periodically interconnected, thus, significantly improving photocatalytic efficiency. The apparent rate constant of IO TiO2 is 9.96 × 10–3 min–1, which is 1.81 times that of powder TiO2. The blue edge of 200 nm IO TiO2 is spectrally closer to the electronic band gap of TiO2. Also, it presents optimal photodegradation efficiency (70.02%), and its rate constant is 2.13 times higher than porous block TiO2 without a band gap. Moreover, a detailed path of a possible reaction mechanism is proposed based on the results of the free radical trapping experiment and EPR analysis. This research offered opportunities for a deeper understanding and more efficient utilization of the blue-edge slow light effect. The slow light can be leveraged to enhance the optical nonlinear effect, which has practical significance for solar energy collection and conversion, optical switches, and photocatalysis. [ABSTRACT FROM AUTHOR]

Polyoxometalate-based nanocomposites with electrocatalytic activity have been applied in hydrogen evolution reactions (HER). Seawater as the main water resource on the earth should be developed as the water electrolysis to prepare high-purity hydrogen. In this paper, we used two synthesis strategies to prepare the nanocomposite Co4-POM@Co-PGDY (Co4-POM: the Kegging-type microcrystals of K10[Co4(PW9O34)2] and Co-PGDY: cobalt-porphyrin linked graphdiyne) with excellent activity for HER. Co-PGDY as the porous material is applied not only as the protection of microcrystals towards the metal ion in seawater but also as the co-electrocatalyst of Co4-POM. Co4-POM@Co-PGDY exhibits excellent HER performance in seawater electrolytes with low overpotential and high stability at high density. Moreover, we have observed a key H3O+ intermediate emergence on the surface of nanocomposite during hydrogen evolution process in seawater by Raman synchrotron radiation-based Fourier transform infrared (SR-FTIR). The results in this paper provide an effective strategy for preparing polyoxometalate-based electrocatalysts with high-performance toward hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

A series of novel Re(I)-based heterobimetallic complexes were synthesized using the ligand p-[N-2-(2′-pyridyl)benzimidazolyl]-[N-2-(2′-pyridyl)indolyl]-benzene (L1), which contains two distinct N^N- and N^C-chelating sites. Their photophysical and electrochemical properties were fully characterized, which unveil the existence of electronic communication between the two metal centers. An electrochemical study shows that these types of Re(I) complex are promising candidates as catalysts for electrocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

A new two-dimensional {Cu6}-added polyoxometalate cluster–organic framework (Cu-POMCOF) was prepared by a hydrothermal method from lacunary polyoxoanions and was applied as a solid support for immobilizing MP-11 and Cyt c. The biocomposite complex exhibits higher stability and catalytic activity than the original free enzyme. [ABSTRACT FROM AUTHOR]

A composite cluster with core–shell structure composed of polyoxometalates (POMs) and graphdiyne (GDY) was synthesized and applied for the electrochemical oxygen evolution reaction (OER). Compared with the original POMs and GDY, the composite cluster Co4(PW9)2@GDY demonstrates superior performance and stable electrochemical OER. The core–shell composite cluster exhibited high performance for OER with low potentials and a small Tafel slope. Moreover, high catalytic activity of the cluster was achieved at a high current density. Co4(PW9)2@GDY has excellent catalytic performance and long stability due to its strong electron-transfer ability in the system, higher conductivity, and the structural advantage of pores in GDY. We also tested the OER synergism mechanism between POM and GDY. This would open access and guide us to synthesize novel clusters based on polyoxometalates and graphdiyne. [ABSTRACT FROM AUTHOR]