High-purity pyrrole-type FeN4 sites have been developed as a superior oxygen reduction catalyst for proton exchange membrane fuel cells.

High-performance electrocatalysts with superior stability are critically important for their practical applications in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, we report a facile method to fabricate urchin-like CoP nanocrystals (NCs) as catalyst for both HER and ORR with desirable electrocatalytic activities and long-term stability. The urchin-like CoP NCs with a diameter of 5 μm were successfully prepared by a hydrothermal reaction following a phosphidation treatment in N2 atmosphere and present excellent HER catalytic performance with a low onset overpotential of 50 mV, a small Tafel slope of 46 mV/decade, and an exceptional low overpotential of ~180 mV at a current density of 100 mA cm(-2) with a mass loading density of 0.28 mg/cm(2). Meanwhile, a remarkable ORR catalytic activity was observed with a half-potential of 0.7 V and an onset potential of 0.8 V at 1600 rpm and a scan rate of 5 mV s(-1). More importantly, the urchin-like CoP NCs present superior stability and keep their catalytic activity for at least 10 000 CV cycles for HER in 0.5 M H2SO4 and over 30 000 s for ORR in 0.1 M KOH, which is ascribed to their robust three-dimensional structure. This urchin-like CoP NCs might be a promising replacement to the Pt-based electrocatalysts in water splitting and fuel cells.

Dual‐sites single atom catalysts hold promise for efficiently regulating multiple reaction processes and explicitly explaining the underlying mechanisms. However, delicate atomic engineering for dual‐site single atom catalysts remains a huge challenge. Herein, atomically dispersed Fe‐Ni single atoms embedded in a nitrogen‐doped carbon matrix (FeNi SAs/NC) are successfully developed with extraordinary activity for electrocatalytic oxygen reduction and evolution reactions (ORR/OER). The atomic FeNi SAs/NC catalyst displays high onset potential (0.98 V) and half‐wave potential (0.84 V) for the ORR, as well as, low overpotential of (270 mV) at 10 mA cm−2 for the OER. The density functional theory calculations indicate that the Fe site as the active center can facilitate the four‐electron reaction process, while Ni sites regulate the electronic structure of Fe sites and further reduce the energy barrier of the rate‐determining step. In addition, the nitrogen‐doped carbon matrix prevents the metal atoms from aggregation and corrosion, leading to the improvement of catalyst durability. As a proof of concept, flexible quasi‐solid‐state zinc– and aluminum–air batteries assembled with the FeNi SAs/NC catalyst exhibit superior peak power densities and discharging specific capacities outperforming the commercial Pt/C. This work provides rational guidance for the synthesis of bifunctional electrocatalysts in next‐generation energy devices for flexible consumer electronics.

Designing definite metal-support interfacial bond is an effective strategy for optimizing the intrinsic activity of noble metals, but rather challenging. Herein, a series of quantum-sized metal nanoparticles (NPs) anchored on nickel metal-organic framework nanohybrids (M@Ni-MOF, M = Ru, Ir, Pd) are rationally developed through a spontaneous redox strategy. The metal-oxygen bonds between the NPs and Ni-MOF guarantee structural stability and sufficient exposure of the surface active sites. More importantly, such precise interfacial feature can effectively modulate the electronic structure of hybrids through the charge transfer of the formed Ni-O-M bridge and then improves the reaction kinetics. As a result, the representative Ru@Ni-MOF exhibits excellent hydrogen evolution reaction (HER) activity at all pH values, even superior to commercial Pt/C and recent noble-metal catalysts. Theoretical calculations deepen the mechanism understanding of the superior HER performance of Ru@Ni-MOF through the optimized adsorption free energies of water and hydrogen due to the interfacial-bond-induced electron redistribution.

Oxygen reduction reaction (ORR) activity can be effectively tuned by modulating the electron configuration and optimizing the chemical bonds. Herein, a general strategy to optimize the activity of metal single‐atoms is achieved by the decoration of metal clusters via a coating–pyrolysis–etching route. In this unique structure, the metal clusters are able to induce electron redistribution and modulate M−N species bond lengths. As a result, M‐ACSA@NC exhibits superior ORR activity compared with the nanoparticle‐decorated counterparts. The performance enhancement is attributed to the optimized intermediates desorption benefiting from the unique electronic configuration. Theoretical analysis reinforces the significant roles of metal clusters by correlating the ORR activity with cluster‐induced charge transfer. As a proof‐of‐concept, various metal–air batteries assembled with Fe‐ACSA@NC deliver remarkable power densities and capacities. This strategy is an effective and universal technique for electron modulation of M−N−C, which shows great potential in application of energy storage devices.

Metal hydroxides and oxides have emerged as fascinating materials and key structures for electrocatalysis, but they are rarely investigated for HER. Herein, we introduce unique transition-metal hydroxides@MXene (TMHs@MXene) hybrids, including...

A novel multifunctional Ag S quantum dot (QD)-based nanomedicine of alendronate (Ald)/doxorubicin (DOX)@Ag S is developed for highly effective bone tumor therapy in an orthotopic model. The bone-targeting and osteolysis inhibition of Ald and the chemotherapeutic effect of DOX on the bone tumor are in situ visualized by Ag S QDs with emission in the second near-infrared window.

carbon-intensive fuels. Hydrogen represents a versatile fuel with high energy density and low carbon emission. In 2020, the global hydrogen generation market size was valued at ≈120 billion USD and is expected to rapidly expand. Presently, industrial hydrogen is primarily acquired from natural gas reforming that involves energy-consuming processes with extensive greenhouse gas release. Alternatively, electrochemical water splitting is a sustainable technique to store the intermittent electricity and produce high-purity hydrogen under ambient condition. [1] The water-splitting process consists of anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER), in which electrocatalysts are particularly vital to lower their energy barriers and reduce the required overpotentials. [2] Currently, precious metal (e.g., Pt) and metal oxides (e.g., RuO 2 , and IrO 2 ) hold the benchmark performance toward HER and OER, respectively. [3] However, their nature scarcity and high cost considerably impede their widespread utilization. Therefore, it is desirable to develop costeffective OER/HER catalysts with active, abundant, and robust surface reactive sites. Non-precious transition metal-based materials, such as oxides, [4] sulfides, [5] LDHs, [6] MOFs, [7] and their composites, [8] have received intensive research in water splitting due to their tunable structure, stability, as well as high reserve. Strategies including morphology and components tuning are applied for advanced electrocatalysts. High material surface area and porosity benefit the intermediate accessibility and fast mass transport during the electrochemical reactions. Researchers pursuit improved electrocatalysis by fabricating porous or hierarchical catalysts with highly exposed reactive sites. [9] However, the synthesis of the highly porous transition metal catalysts with the controlled crystalline phase using the traditional template strategy often needs tedious and timeconsuming manufacturing. In addition, regarding the required bifunctionality (i.e., OER and HER) for water splitting, the integration of different nanostructures by heterostructure fabrication is adopted for further optimizing the electrocatalytic performance. The interface engineering and electronic regulation facilitate the optimized chemisorption of the reaction Developing efficient bifunctional electrocatalysts toward oxygen/hydrogen evolution reactions is crucial for electrochemical water splitting toward hydrogen production. The high-performance electrocatalysts depend on the catalytically active and highly accessible reaction sites and their structural robustness, while the rational design of such electrocatalysts with desired features avoiding tedious manufacture is still challenging. Here, a facile method is reported to synthesize mesoporous and heterostructured transition metal oxides strongly anchored on a nickel skeleton (MH-TMO) containing identified Fe-Cu oxide interfaces with high intrinsic activity, easy accessibility for reaction intermediates, ...