The role of vacancy defects is demonstrated to be positive in various energy‐related processes. However, introducing vacancy defects into single‐crystalline nanostructures with given facets and studying their defect effect on electrocatalytic properties remains a great challenge. Here this study deliberately introduces oxygen defects into single‐crystalline ultrathin Co3O4 nanosheets with O‐terminated {111} facets by mild solvothermal reduction using ethylene glycol under alkaline condition. As‐prepared defect‐rich Co3O4 nanosheets show a low overpotential of 220 mV with a small Tafel slope of 49.1 mV dec−1 for the oxygen evolution reaction (OER), which is among the best Co‐based OER catalysts to date and even more active than the state‐of‐the‐art IrO2 catalyst. Such vacancy defects are formed by balancing with reducing environments under solvothermal conditions, but are surprisingly stable even after 1000 cycles of scanning under OER working conditions. Density functional theory plus U calculation attributes the enhanced performance to the oxygen vacancies and consequently exposed second‐layered Co metal sites, which leads to the lowered OER activation energy of 2.26 eV and improved electrical conductivity. This mild solvothermal reduction concept opens a new door for the understanding and future designing of advanced defect‐based electrocatalysts.

show superb activities than either of the parent metal catalyst, and comparable to the best noble catalysts (e.g., IrO 2 and RuO 2 ) [ 12 ] for oxygen evolution reaction (OER), which is a key component for a number of energy storage and conversion processes. [ 13 ] However, the lack of investigations on the oxygen reduction reaction (ORR) activities of LDHs greatly limits their further application in rechargeable metal-air battery and unitized regenerative fuel cell. Thus it is intriguing to evaluate the bifunctional performance of LDH-based materials in order to broadening the usages in electrochemistry.The specifi c activity of the material for the target reaction is usually highly dependent on the chemical composition and their electronic structures. [ 14,15 ] For OER, it is found that a small amount of Fe doping was effective for enhancing the OER activities of Ni hydroxides or oxides, possibly due to the enhanced structure disorder and conductivity. [ 16 ] Recently, an excellent OER performance was observed on amorphous NiCoFe oxides which were prepared by a photochemical route. [ 17 ] As to the ORR, Co and Fe ions are believed to be the active center with specifi c crystal and electronic structures. [ 18,19 ] Moreover, Co-based compounds have been widely studied recently as bifunctional materials for oxygen electrocatalysis. [ 20 ] LDHs, which offer a wide tunability of diverse metal species and ratios in the intralayer as well as a large interlayer spacing which may accelerate the ion diffusion, should be of great potential with high bifunctional performance.In this work, the ORR and OER activities of trinary NiCoFe-LDHs have been systematically investigated. It is observed that the NiCoFe-LDH showed a reasonable bifunctional performance while the sample after preoxidation treatment (denoted as O-NiCoFe-LDH) would lead to a signifi cant enhancement. This improvement was attributed to the formation of Co 3+ in the intralayer, result in the conductivity improvement of the material. To demonstrate the practical application of the LDH catalyst, the O-NiCoFe-LDH loaded on Tefl on-treated carbon fi ber paper (T-CFP) only required a potential hysteresis of ≈800 mV to achieve stable current densities of ≈20 mA cm −2 for ORR and OER for matching the current requirement of rechargeable zinc-air batteries, [ 21 ] much smaller than those of the commercial 60 wt% Pt/C and 20 wt% Ir/C catalysts. This fi rst investigation on the bifunctional performance of LDHs not Layered double hydroxides (LDHs) are a family of high-profi le layer materials with tunable metal species and interlayer spacing, and herein the LDHs are fi rst investigated as bifunctional electrocatalysts. It is found that trinary LDH containing nickel, cobalt, and iron (NiCoFe-LDH) shows a reasonable bifunctional performance, while exploiting a preoxidation treatment can signifi cantly enhance both oxygen reduction reaction and oxygen evolution reaction activity. This phenomenon is attributed to the partial conversion of Co 2+ to Co 3+ state in the pr...

By delivering the concept of clean hydrogen energy and green catalysis to the biomedical field, engineering of hydrogen-generating nanomaterials for treatment of major diseases holds great promise. Leveraging virtue of versatile abilities of Pd hydride nanomaterials in high/stable hydrogen storage, self-catalytic hydrogenation, near-infrared (NIR) light absorption and photothermal conversion, here we utilize the cubic PdH0.2 nanocrystals for tumour-targeted and photoacoustic imaging (PAI)-guided hydrogenothermal therapy of cancer. The synthesized PdH0.2 nanocrystals have exhibited high intratumoural accumulation capability, clear NIR-controlled hydrogen release behaviours, NIR-enhanced self-catalysis bio-reductivity, high NIR-photothermal effect and PAI performance. With these unique properties of PdH0.2 nanocrystals, synergetic hydrogenothermal therapy with limited systematic toxicity has been achieved by tumour-targeted delivery and PAI-guided NIR-controlled release of bio-reductive hydrogen as well as generation of heat. This hydrogenothermal approach has presented a cancer-selective strategy for synergistic cancer treatment.

Exploring materials with regulated local structures and understanding how the atomic motifs govern the reactivity and durability of catalysts are a critical challenge for designing advanced catalysts. Herein we report the tuning of the local atomic structure of nickel-iron layered double hydroxides (NiFe-LDHs) by partially substituting Ni with Fe to introduce Fe-O-Fe moieties. These Fe -containing NiFe-LDHs exhibit enhanced oxygen evolution reaction (OER) activity with an ultralow overpotential of 195 mV at the current density of 10 mA cm , which is among the best OER catalytic performance to date. In-situ X-ray absorption, Raman, and electrochemical analysis jointly reveal that the Fe-O-Fe motifs could stabilize high-valent metal sites at low overpotentials, thereby enhancing the OER activity. These results reveal the importance of tuning the local atomic structure for designing high efficiency electrocatalysts.

Layered double hydroxides (LDHs) are a family of layer materials that receive heightened attention. Herein a ternary NiFeMn-LDH is investigated with superior oxygen evolution activity, which is attributed to the Mn(4+) doping in the intralayer, which modifies the electronic structure and improves the conductivity of the electrocatalyst.