Utilizing clean energy derived from photoelectrocatalytic reactions is expected to be an excellent choice to fundamentally solve the problem of the human energy crisis. Photoelectrochemical (PEC) cell can effectively promote charge separation and improve solar energy conversion efficiency since it combines the advantages of photocatalysis and electrocatalysis. However, the hole transfer and subsequent oxidation reaction in the PEC process are slow, resulting in the rapid recombination of photogenerated electron-hole pairs and low PEC performance. The half-oxidation reaction involving photogenerated holes is the bottleneck of PEC water splitting. Therefore, hole modulation has been an important research area in the field of catalysis. However, compared with electron modulation, research on hole modulation is limited and still faces great challenges. It is therefore of great significance to develop effective modulation strategies for photogenerated holes. This review summarizes the hole modulation strategies developed in the last five years, including hole sacrificial agents, nanostructural modification, heterostructure construction and cocatalyst modification. Hole modulation dynamics studies, such as transient absorption spectroscopy, time-resolved photoluminescence spectroscopy, transient photovoltage and scanning electrochemical microscopy, are also summarized. Moreover, relevant conclusions and an outlook are proposed.

Dielectric capacitors with ultrafast charge-discharge rates are extensively used in electrical and electronic systems. To meet the growing demand for energy storage applications, researchers have devoted significant attention to dielectric ceramics with excellent energy storage properties. As a result, the awareness of the importance of the pulsed discharge behavior of dielectric ceramics and conducting characterization studies has been raised. However, the temperature stability of pulsed discharge behavior, which is significant for pulsed power applications, is still not given the necessary consideration. Here, we systematically investigate the microstructures, energy storage properties and discharge behaviors of nanograined (1-x)BaTiO₃-xNaNbO₃ ceramics prepared by a two-step sintering method. The 0.60BaTiO₃-0.40NaNbO₃ ceramics with relaxor ferroelectric characteristics possess an optimal discharge energy density of 3.07 J cm^-3, a high energy efficiency of 92.6%, an ultrafast discharge rate of 39 ns and a high power density of 100 MW cm^-3. In addition to stable energy storage properties in terms of frequency, fatigue and temperature, the 0.60BaTiO₃-0.40NaNbO₃ ceramics exhibit temperature-stable power density, thereby illustrating their significant potential for power electronics and pulsed power applications.

Ultrafine-grained (UFG) metallic materials processed by severe plastic deformation (SPD) techniques often exhibit significantly higher strengths than those calculated by the well-known Hall-Petch equation. These higher strengths result from the fact that SPD processing not only forms the UFG structure but also leads to the formation of other nanostructural features, including dislocation substructures, nanotwins and nanosized second-phase precipitations, which further contribute to the hardening. Moreover, the analysis of strengthening mechanisms in recent studies demonstrates an important contribution to the hardening due to phenomena related to the structure of grain boundaries as a non-equilibrium state and the presence of grain boundary segregations. Herein, the principles of the nanostructural design of metallic materials for superior strength using SPD processing are discussed.

Broadband photodetectors covering the ultraviolet (UV) to visible range are significant for applications in communication and imaging. Broadband photodetectors with the capacity to distinguish wavelength bands are highly desirable because they can provide additional spectral information. Herein, we report a UV-visible distinguishable broadband photodetector based on a graphene/ZnO quantum dot heterostructure. The photodetector exhibits negative photoconductance under visible illumination because the adsorbents on graphene act as scattering centers to reduce the carrier mobility. In contrast, under UV illumination, the photodetector shows positive photoconductance as the photogenerated electrons in the ZnO quantum dots transfer to the graphene, thereby increasing the conductivity. Thus, the detection and distinction of UV and visible illumination can be realized by utilizing the opposing photoconductivity changes. These results offer inspiration for the design of multifunctional broadband photodetectors.

High entropy alloys (HEAs), as a new class of structural materials, have attracted extensive interest from numerous metallurgical scientists and engineers. Benefiting from their unique microstructural features and outstanding mechanical performance, HEAs have shown significant potential for applications in many engineering fields, even under extreme conditions. In particular, when exposed to hydrogen and/or intermediate-temperature environments, these HEAs inevitably suffer from severe environmental embrittlement (EE) issues, e.g., hydrogen embrittlement (HE) and intermediate-temperature embrittlement (ITE), resulting in serious premature intergranular failure. In this work, we critically review the state-of-the-art advances of EE in previously reported HEA systems. Particular focus is given to novel strategies to enhance the resistance to EE in different HEAs. Two critical embrittlement phenomena, namely, HE and ITE, are highlighted separately. Finally, we provide perspectives on future research directions and opportunities for EE-resistant HEAs.

Antiferroelectrics are a kind of unique dielectric materials, mainly due to their polarization behavior, and composition-induced antiferroelectricity stability also draws considerable attention. In this work, single orthorhombic phase (Pb_0.95Bi_0.05)ZrO₃ (PBZ), Pb(Zr_0.95Bi_0.05)O₃ (PZB), and PbZrO₃ (PZO) films with good density and flatten surface was prepared on Pt/Ti/SiO₂/Si substrate via sol-gel method. Compared with pure PZO films, the PBZ and PZB films possess increased switching electric field difference Δ E due to enhanced forward switching field and the late response of backward switching field. In terms of stabilizing AFE phase, changing the tolerance factor t has the similar effect as Bi-doping the A/B sites in PZO, with the modification of the A-site being more effective than that of the B-site. PBZ films achieve a high recoverable energy density (W_rec) of 26.4 J/cm³ with energy efficiency (η) of 56.2% under an electric field of 1278 kV/cm, which exceeds other pure AFE materials. This work provides a fundamental understanding of the crystal structure-related antiferroelectricity of PZO materials and broadens the chemical doping route to enhance the electric properties of AFE materials.

The development of dielectric capacitors with high energy density and energy efficiency is of great significance in the modern electronic components market. To reduce the high energy loss of Bi_0.5Na_0.5TiO₃, 0.55Bi_0.5Na_0.5TiO₃-0.45(Sr_0.7Bi_0.2)TiO₃ (BNT-BST) nanofibers with a high aspect ratio are synthesized via electrospinning. To achieve a high energy density, the design of a symmetric trilayer nanocomposite consisting of a BNT-BST/polyvinylidene difluoride (PVDF) layer with a high dielectric constant sandwiched between two layers of pure PVDF is herein described. The trilayer structure can effectively alleviate the electric field concentration effect, resulting in a considerably enhanced breakdown strength and improved discharge energy density. The maximum discharge energy density of 17.37 J/cm³ at 580 kV/mm could be achieved in the symmetric trilayer nanocomposite with a BNT-BST/PVDF middle layer, which is 90.5% greater than that achieved using pure PVDF (9.21 J/cm³ at 450 kV/mm). This study presents a new case for developing dielectric capacitors with high energy density.