Heterogeneous Fe-Doped Ni(OH)2 Grown on Nickel Mesh by Electrodeposition for Efficient Alkaline Oxygen Evolution Reaction.

Designing highly excellent and stable catalysts for alkaline oxygen evolution reaction (OER) is gradually pivotal for clean energy development. In this work, a heterogeneous Fe-doped Ni(OH)2 (Ni/Fe-0.1) was developed via simple one-step electrodeposition onto nickel mesh. The heterogeneous interface structure generates sufficient active sites, significantly improving OER performance with an overpotential of 174 mV at 10 mA cm-2 (η10 ), while Tafel slope is only 43.0 mV dec-1 . In particular, Ni/Fe-0.1 is still able to operate stably at a current density of 1 A cm-2 for 100 h without obvious potential decay. The oxidation of Ni2+ to Ni3+ was detected by X-ray photoelectron spectroscopy, proving that the heterogeneous catalyst could stabilize the high-valence state of nickel as active sites to its superior OER performance. This work provides a convenient synthetic strategy for forming heterogeneous catalysts toward efficient water electrolysis.

Amorphous Oxysulfide Reconstructed from Spinel NiCo2 S4 for Efficient Water Oxidation.

The progress of effective and durable electrocatalysts for oxygen evolution reaction (OER) is urgent, which is essential to promote the overall efficiency of green hydrogen production. To improve the performance of spinel cobalt-based oxides, which serve as promising water oxidation electrocatalysts in alkaline electrolytes, most researches have been concentrated on cations modification. Here, an anionic regulation mechanism is employed to adopt sulfur(S) anion substitution to supplant NiCo2 O4 by NiCo2 S4 , which contributed to an impressive OER performance in alkali. It is revealed that the substitution of S constructs a sub-stable spinel structure that facilitates its reconstruction into active amorphous oxysulfide under OER conditions. More importantly, as the active phase in the actual reaction process, the hetero-anionic amorphous oxysulfide has an appropriately tuned electronic structure and efficient OER electrocatalytic activity. This work demonstrates a promising approach for achieving anion conditioning-based tunable structure reconstruction for robust and easy preparation spinel oxide OER electrocatalysts.

Cu(I) Metal-Organic Framework Composites with AgCl/Ag Nanoparticles for Irradiation-Enhanced Antibacterial Activity against E. coli.

Metal-organic frameworks (MOFs) have emerged as prospective antibacterial agents or synergistic agents for their versatile chemical building components and structures. In this work, copper(I) halide MOFs of Cu(I)bpyCl (bpy = 4,4'-bipyridine) composited with AgCl/Ag nanoparticles were synthesized, and their antibacterial activities were measured against Escherichia coli and Staphylococcus aureus. The attached chlorine in Cu(I)2Cl2 nodes of the MOFs served as loading sites for silver ions, in which AgCl and concomitant metallic Ag nanoparticles were in situ generated. Exceptional antibacterial activity against E. coli was realized with a minimum inhibitory concentration (MIC) of ∼7.8 µg mL-1, while the MIC value was ∼16 µg mL-1 against S. aureus. Enhanced antibacterial activity against E. coli with light irradiation was measured by the disk diffusion method compared with that under dark conditions.

Oxygen Evolution Electrocatalysts for the Proton Exchange Membrane Electrolyzer: Challenges on Stability.

Hydrogen generated by proton exchange membrane (PEM) electrolyzer holds a promising potential to complement the traditional energy structure and achieve the global target of carbon neutrality for its efficient, clean, and sustainable nature. The acidic oxygen evolution reaction (OER), owing to its sluggish kinetic process, remains a bottleneck that dominates the efficiency of overall water splitting. Over the past few decades, tremendous efforts have been devoted to exploring OER activity, whereas most show unsatisfying stability to meet the demand for industrial application of PEM electrolyzer. In this review, systematic considerations of the origin and strategies based on OER stability challenges are focused on. Intrinsic deactivation of the material and the extrinsic balance of plant-induced destabilization are summarized. Accordingly, rational strategies for catalyst design including doping and leaching, support effect, coordination effect, strain engineering, phase and facet engineering are discussed for their contribution to the promoted OER stability. Moreover, advanced in situ/operando characterization techniques are put forward to shed light on the OER pathways as well as the structural evolution of the OER catalyst, giving insight into the deactivation mechanisms. Finally, outlooks toward future efforts on the development of long-term and practical electrocatalysts for the PEM electrolyzer are provided.

In Operando Identification of In Situ Formed Metalloid Zincδ+ Active Sites for Highly Efficient Electrocatalyzed Carbon Dioxide Reduction.

Electrochemical CO2 -to-CO conversion provides a possible way to address problems associated with the greenhouse effect; however, developing low-cost electrocatalysts to mediate high-efficiency CO2 reduction remains a challenge on account of the limited understanding of the nature of the real active sites. Herein, we reveal the Znδ+ metalloid sites as the real active sites of stable nonstoichiometric ZnOx structure derived from Zn2 P2 O7 through operando X-ray absorption fine structure analysis in conjunction with evolutionary-algorithm-based global optimization. Furthermore, theoretical and experimental results demonstrated that Znδ+ metalloid active sites could facilitate the activation of CO2 and the hydrogenation of *CO2 , thus accelerating the CO2 -to-CO conversion. Our work establishes a critical fundamental understanding of the origin of the real active center in the zinc-based electrocatalysts for CO2 reduction reaction.

Highly Ethylene-Selective Electrocatalytic CO2 Reduction Enabled by Isolated Cu-S Motifs in Metal-Organic Framework Based Precatalysts.

Copper-based materials are efficient electrocatalysts for the conversion of CO2 to C2+ products, and most these materials are reconstructed in situ to regenerate active species. It is a challenge to precisely design precatalysts to obtain active sites for the CO2 reduction reaction (CO2 RR). Herein, we develop a strategy based on local sulfur doping of a Cu-based metal-organic framework precatalyst, in which the stable Cu-S motif is dispersed in the framework of HKUST-1 (S-HKUST-1). The precatalyst exhibits a high ethylene selectivity in an H-type cell with a maximum faradaic efficiency (FE) of 60.0 %, and delivers a current density of 400 mA cm-2 with an ethylene FE up to 57.2 % in a flow cell. Operando X-ray absorption results demonstrate that Cuδ+ species stabilized by the Cu-S motif exist in S-HKUST-1 during CO2 RR. Density functional theory calculations indicate the partially oxidized Cuδ+ at the Cu/Cux Sy interface is favorable for coupling of the *CO intermediate due to the modest distance between coupling sites and optimized adsorption energy.

One-step coating of commercial Ni nanoparticles with a Ni, N-co-doped carbon shell towards efficient electrocatalysts for CO2 reduction.

Commercial nickel nanoparticles (Ni NPs) were directly converted to efficient electrocatalysts for CO2 reduction by urea-Ni solid powder pyrolysis, in which a Ni, N-co-doped graphite carbon shell wraps the Ni NPs in situ. 98.3% CO selectivity was realized with a current density of -20.2 mA cm-2 and an overpotential of 0.69 V.

Boosting Alkaline Hydrogen Evolution Electrocatalysis over Metallic Nickel Sites through Synergistic Coupling with Vanadium Sesquioxide.

For renewable and sustainable energy, developing cut-price and high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) by alkaline water electrolysis is of paramount importance. In this study, a compound electrocatalyst composed of nickel-vanadium sesquioxide nanoparticles supported on porous nickel foam (Ni-V2 O3 /NF) is found to exhibit electrocatalytic performance towards HER that is superior to that of the commercial Pt/C catalyst, with nearly zero onset overpotential, an extremely low overpotential of 25 mV to obtain a current density of -10 mA cm-2 , a Tafel slope of 58 mV dec-1 , and a good durability for 24 h in 1.0 m KOH. Theoretical calculations reveal that the presence of V2 O3 optimizes the electronic structure of active Ni components and continuously accelerates the dissociation of water molecules, which in turn improves the HER kinetics. The present work will advance the development of highly efficient nanocomposite electrocatalysts for alkaline water electrocatalysis.

Hierarchical Porous Zr-Based MOFs Synthesized by a Facile Monocarboxylic Acid Etching Strategy.

A new monocarboxylic acid etching (MAE) strategy was developed for transforming chemically stable Zr-based metal-organic frameworks (MOFs) of UiO-66 to their hierarchical porous counterpart. The key design element was based on the incomplete replacement of bridging ligands in MOFs by monocarboxylic acids (MAs), leading to the departure of partial ligands and metal clusters to create mesopores in MOFs. A series of MAs with different acidity and carbon chain length were tested, and propionic acid (PA) was screened to be the suitable choice. The textural features including pore size distribution, specific surface area, and pore volume of the obtained products can be controlled by adjusting the MA concentration and reaction temperature. The obtained hierarchical porous MOFs inherited excellent stability from their parent materials. Additionally, the MAE strategy was universal to construct hierarchical porous Zr-based MOFs, and it was expanded to etch UiO-66 derivatives. The excellent adsorption behavior of the resultant hierarchical porous Zr-based MOFs over two enzymes with different size was also successfully exemplified, demonstrating their application potentials with bulky molecules involved.

Ultrasmall Biocompatible Bi2Se3 Nanodots for Multimodal Imaging-Guided Synergistic Radiophotothermal Therapy against Cancer.

Sub-3 nm ultrasmall Bi2Se3 nanodots stabilized with bovine serum albumin were successfully synthesized through a reaction of hydroxyethylthioselenide with bismuth chloride in aqueous solution under ambient conditions. These nanodots exhibit a high photothermal conversion efficiency (η = 50.7%) due to their strong broad absorbance in the near-infrared (NIR) window and serve as a nanotheranostic agent for photoacoustic imaging and photothermal cancer therapy. In addition, they also display radioenhancement with a ratio of 6% due to their sensitivity to X-rays, which makes them a potential sensitizer for radiotherapy. These nanodots were also labled with radioactive 99mTc for quantification of their biodistribution by single-photon-emission computed tomography (SPECT)/computed tomography (CT) imaging. Our work demonstrates the potential of ultrasmall Bi2Se3 nanodots in multimodal imaging-guided synergetic radiophotothermal therapy of cancer.