Piezoelectric materials, which respond mechanically to applied electric field and vice versa, are essential for electromechanical transducers. Previous theoretical analyses have shown that high piezoelectricity in perovskite oxides is associated with a flat thermodynamic energy landscape connecting two or more ferroelectric phases. Here, guided by phenomenological theories and phase-field simulations, we propose an alternative design strategy to commonly used morphotropic phase boundaries to further flatten the energy landscape, by judiciously introducing local structural heterogeneity to manipulate interfacial energies (that is, extra interaction energies, such as electrostatic and elastic energies associated with the interfaces). To validate this, we synthesize rare-earth-doped Pb(MgNb)O-PbTiO (PMN-PT), as rare-earth dopants tend to change the local structure of Pb-based perovskite ferroelectrics. We achieve ultrahigh piezoelectric coefficients d of up to 1,500 pC N and dielectric permittivity ε/ε above 13,000 in a Sm-doped PMN-PT ceramic with a Curie temperature of 89 °C. Our research provides a new paradigm for designing material properties through engineering local structural heterogeneity, expected to benefit a wide range of functional materials.

highly dependent on the adsorption model of oxygen molecules (O 2 ) on the surface of catalysts. [2] The side-on adsorption with a "*O-O*" configuration (* presents the active site) is conducive to weakening the O-O bond for reduction of O 2 into H 2 O via a four-electron (4e) ORR pathway, [3] while the end-on configuration formed by a solo oxygen atom coordinated on a single active site ("*OOH" intermediate) facilitates to selectively catalyzing oxygen to generate H 2 O 2 via a two-electron (2e) ORR pathway. [4] To realize 2e oxygen electroreduction, various strategies including alloying, [5] chemical functionalization, [6] downsizing, [7] and single-atom engineering [8] have been developed to regulate the physicochemical properties of the catalysts. Though substantial progress has been made, the activity and durability of reported works still cannot compete with the demand of the practical application. [9] The cation vacancy engineering strategy could be an effective approach to develop high-performance catalysts for the electrocatalytic synthesis of H 2 O 2 owing to the following merits: creating cation vacancy on host materials can prolong the distance or spacing of the active sites, thereby leading to the formation of *OOH adsorption favorable; [4a] the charge density between active sites and adjacent coordination atoms will be redistributed, which optimizes the Electrocatalytic hydrogen peroxide (H 2 O 2 ) synthesis via the two-electron oxygen reduction reaction (2e ORR) pathway is becoming increasingly important due to the green production process. Here, cationic vacancies on nickel phosphide, as a proof-of-concept to regulate the catalyst's physicochemical properties, are introduced for efficient H 2 O 2 electrosynthesis. The as-fabricated Ni cationic vacancies (V Ni )-enriched Ni 2−x P-V Ni electrocatalyst exhibits remarkable 2e ORR performance with H 2 O 2 molar fraction of >95% and Faradaic efficiencies of >90% in all pH conditions under a wide range of applied potentials. Impressively, the as-created V Ni possesses superb longterm durability for over 50 h, suppassing all the recently reported catalysts for H 2 O 2 electrosynthesis. Operando X-ray absorption near-edge spectroscopy (XANES) and synchrotron Fourier transform infrared (SR-FTIR) combining theoretical calculations reveal that the excellent catalytic performance originates from the V Ni -induced geometric and electronic structural optimization, thus promoting oxygen adsorption to the 2e ORR favored "end-on" configuration. It is believed that the demonstrated cation vacancy engineering is an effective strategy toward creating active heterogeneous catalysts with atomic precision.

Carbon nanotubes increase electrochemically active surface area and reduce charge transfer resistance of transition metal borides.

Compactness and versatility of fiber-based micro-supercapacitors (FMSCs) make them promising for emerging wearable electronic devices as energy storage solutions. But, increasing the energy storage capacity of microscale fiber electrodes, while retaining their high power density, remains a significant challenge. Here, this issue is addressed by incorporating ultrahigh mass loading of ruthenium oxide (RuO ) nanoparticles (up to 42.5 wt%) uniformly on nanocarbon-based microfibers composed largely of holey reduced graphene oxide (HrGO) with a lower amount of single-walled carbon nanotubes as nanospacers. This facile approach involes (1) space-confined hydrothermal assembly of highly porous but 3D interconnected carbon structure, (2) impregnating wet carbon structures with aqueous Ru ions, and (3) anchoring RuO nanoparticles on HrGO surfaces. Solid-state FMSCs assembled using those fibers demonstrate a specific volumetric capacitance of 199 F cm at 2 mV s . Fabricated FMSCs also deliver an ultrahigh energy density of 27.3 mWh cm , the highest among those reported for FMSCs to date. Furthermore, integrating 20 pieces of FMSCs with two commercial flexible solar cells as a self-powering energy system, a light-emitting diode panel can be lit up stably. The current work highlights the excellent potential of nano-RuO -decorated HrGO composite fibers for constructing micro-supercapacitors with high energy density for wearable electronic devices.

Ag is a promising electrocatalyst for electrochemical reduction of CO 2 to CO due to its relatively low cost and high activity. However, it is challenging to achieve high reaction rates while maintaining good selectivity. Here, we used an H 2 bubbletemplated electrodeposition method in a thiocyanate (SCN)containing aqueous electrolyte to synthesize a hierarchically porous Ag nanofoam (AgNF) with curved Ag surfaces modified by SCN. This AgNF demonstrates excellent performance for CO 2 reduction with a high CO Faradaic efficiency (FE CO ) of 97%. It can maintain over 90% FE CO in a wide potential window (−0.5 to −1.2 V RHE ), enabling the maximum CO selective current density of 33 mA cm −2 and the mass activity of 23.5 A g Ag −1, which are the highest values among recently reported Ag-based electrocatalysts. Mechanism studies reveal that the catalytic performance of the AgNF correlates with the density of surface SCN ligands, which exhibit excellent electrochemical stability under negative potentials. Density functional theory calculations suggest that SCN ligands promote the formation of COOH* intermediates by modifying the local electron density at the active sites. Further, the synthesis method is applicable to different catalyst substrates. For example, the AgNF grown on a carbon-based gas diffusion film exhibits an ultrahigh mass activity of 52.1 A g Ag −1 and maintains its high CO selectivity simultaneously, demonstrating excellent potentials for practical applications.