Self-Template Synthesis of Co-Se-S-O Hierarchical Nanotubes as Efficient Electrocatalysts for Oxygen Evolution under Alkaline and Neutral Conditions

Supramolecular Anchoring of Fe(III) Molecular Redox Catalysts into Graphitic Surfaces Via CH-π and π-π Interactions for CO2 Electroreduction

Photoelectrochemical devices require solid anodes and cathodes for the easy assembling of the whole cell and thus redox catalysts need to be deposited on the electrodes. Typical catalyst deposition involves drop casting, spin coating, doctor blading or related techniques to generate modified electrodes where the active catalyst in contact with the electrolyte is only a very small fraction of the deposited mass. We have developed a methodology where the redox catalyst is deposited at the electrode based on supramolecular interactions, namely CH-π and π-π between the catalyst and the surface. This generates a very well-defined catalysts-surface structure and electroactivity, together with a very large catalytic response. This approach represents a new anchoring strategy that can be applied to catalytic redox reactions in heterogeneous phase and compared to traditional methods involves about 4-5 orders of magnitude less mass deposition to achieve comparable activity and with very well-behaved electroactivity and stability.

S-Doped NiFe2O4 Nanosheets Regulated Microbial Community of Suspension for Constructing High Electroactive Consortia

Iron-based nanomaterials (NMs) are increasingly used to promote extracellular electron transfer (EET) for energy production in bioelectrochemical systems (BESs). However, the composition and roles of planktonic bacteria in the solution regulated by iron-based NMs have rarely been taken into account. Herein, the changes of the microbial community in the solution by S-doped NiFe₂O₄ anodes have been demonstrated and used for constructing electroactive consortia on normal carbon cloth anodes, which could achieve the same level of electricity generation as NMs-mediated biofilm, as indicated by the significantly high voltage response (0.64 V) and power density (3.5 W m⁻²), whereas with different microbial diversity and connections. Network analysis showed that the introduction of iron-based NMs made Geobacter positively interact with f_Rhodocyclaceae, improving the competitiveness of the consortium (Geobacter and f_Rhodocyclaceae). Additionally, planktonic bacteria regulated by S-doped anode alone cannot hinder the stimulation of Geobacter by electricity and acetate, while the assistance of lining biofilm enhanced the cooperation of sulfur-oxidizing bacteria (SOB) and fermentative bacteria (FB), thus promoting the electroactivity of microbial consortia. This study reveals the effect of S-doped NiFe₂O₄ NMs on the network of microbial communities in MFCs and highlights the importance of globality of microbial community, which provides a feasible solution for the safer and more economical environmental applications of NMs.

Hierarchical NiFeV Hydroxide Nanotubes: Synthesis, Topotactic Transformation and Electrocatalysis towards Oxygen Evolution Reaction

Electrocatalytic overall water splitting is a sustainable approach to realizing the clean production of hydrogen energy, however, is mainly hindered by the sluggish kinetics of oxygen evolution reaction (OER) half...

Iron, rhodium-codoped Ni2P nanosheets arrays supported on nickel foam as an efficient bifunctional electrocatalyst for overall water splitting

To enhance the overall water splitting efficiency, it is widely attractive yet challenging to develop low price, abundance and efficient bifunctional electrocatalysts towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, Fe,Rh-codoped Ni₂P nanosheets arrays were in situ anchored on three-dimension (3D) Ni foam under hydrothermal condition and successive phosphorization, denoted as Fe,Rh-Ni₂P/NF for simplicity. The unique nanosheets arrays effectively enriched the active sites with easy accessibility. By virtue of the unique sheet-like arrays and 3D porous conductive substrate, the prepared Fe,Rh-Ni₂P/NF showed the low overpotentials of 226 mV at 30 mA cm^-2 towards the OER and 73 mV at 10 mA cm^-2 for the HER. Moreover, the electrocatalyst effectively worked as anode and cathode for overall water splitting system, showing a small voltage of 1.62 V to drive a current density of 10 mA cm^-2. The present work provides alternative option for fabricating advanced catalysts in electrocatalysis and energy devices.

Selenium uptake and simultaneous catalysis of sulfite oxidation in ammonia-based desulfurization

Accelerating the (NH₄)₂SO₃ oxidation gives rise to the reclaiming of byproduct, while there are secondary environmental risks from reduction of the coexisted selenium species by sulfite. In this study, a bi-functional Co-SBA-15-SH, were synthesized through Co impregnation and sulfhydryl (-SH) decoration, which can simultaneously uptake Se and accelerate sulfite oxidation efficiently. Meanwhile, the adsorption kinetics and migration mechanism of Se species were revealed through characterization and density functional calculations, with maximum adsorption capacity of 223 mg/g. The inhibition of Se⁰ re-emission and poisonous effect of Se on sulfite oxidation was also investigated. Using the findings of this study, the ammonia desulfurization can be improved by enabling purification of the byproduct and lowering the toxicity of effluent by removing toxic pollutants.

A “Superaerophobic” Se-Doped CoS2 Porous Nanowires Array for Cost-Saving Hydrogen Evolution

The pursuit of low-cost and high-efficiency catalyst is imperative for the development and utilization of hydrogen energy. Heteroatomic doping which is conducive to the redistribution of electric density is one of the promising strategies to improve catalytic activity. Herein, the Se-doped CoS2 porous nanowires array with a superaerophobic surface was constructed on carbon fiber. Due to the electronic modulation and the unique superaerophobic structure, it showed improved hydrogen evolution activity and stability in urea-containing electrolyte. At a current density of 10 mA cm−2, the overpotentials are 188 mV for hydrogen evolution reaction (HER) and 1.46 V for urea oxidation reaction (UOR). When it was set as a cell, the voltage is low as 1.44 V. Meanwhile, the current densities of HER and UOR, as well as of cell remained basically unchanged after a continuous operation for 48 h. This work opens up a new idea for designing of cost-saving hydrogen evolution electrocatalysts.

Self-supported cobalt–nickel bimetallic telluride as an advanced catalyst for the oxygen evolution reaction

The Ni-doped Co@CoTe2 electrode exhibits an outstanding OER activity and excellent long-term stability and outperforms most of the well-studied Co-based dichalcogenides.

Nano-Modified Titanium Implant Materials: A Way Toward Improved Antibacterial Properties

Titanium and its alloys have superb biocompatibility, low elastic modulus, and favorable corrosion resistance. These exceptional properties lead to its wide use as a medical implant material. Titanium itself does not have antibacterial properties, so bacteria can gather and adhere to its surface resulting in infection issues. The infection is among the main reasons for implant failure in orthopedic surgeries. Nano-modification, as one of the good options, has the potential to induce different degrees of antibacterial effect on the surface of implant materials. At the same time, the nano-modification procedure and the produced nanostructures should not adversely affect the osteogenic activity, and it should simultaneously lead to favorable antibacterial properties on the surface of the implant. This article scrutinizes and deals with the surface nano-modification of titanium implant materials from three aspects: nanostructures formation procedures, nanomaterials loading, and nano-morphology. In this regard, the research progress on the antibacterial properties of various surface nano-modification of titanium implant materials and the related procedures are introduced, and the new trends will be discussed in order to improve the related materials and methods.

3D hollow Co-Fe-P nanoframes immobilized on N,P-doped CNT as an efficient electrocatalyst for overall water splitting

The rational design of nonprecious and high-efficiency bifunctional electrocatalysts with advanced structural and compositional preponderance for water electrolysis is of paramount importance for the generation of sustainable and clean energy. Herein, for the first time, a novel three-dimensional (3D) hollow hybrid electrocatalyst, Co-Fe-P nanoframe immobilized on N,P-doped carbon nanotubes (CoFeP NFs/NPCNT), was synthesized by selectively etching a CNT-composited Co,Fe-based Prussian blue analogue and subsequent phosphorization. Benefiting from its unique 3D hollow nanoarchitecture, which offers rich porosity and abundant catalytically active sites and guarantees excellent conductivity and structural stability, the hollow CoFeP NFs/NPCNT hybrid delivered pronounced catalytic activity for oxygen evolution (or hydrogen evolution) in alkaline electrolyte, with a low overpotential of 278 (or 132) mV at 10 mA cm-2, small Tafel slope of 39.5 (or 62.9) mV dec-1 and prominent long-term stability. Therefore, when CoFeP NFs/NPCNT was employed as the cathode and anode toward overall water-splitting, it required a quite small cell voltage of only 1.56 V to afford a current density of 10 mA cm-2, and displayed outstanding electrocatalytic stability over 60 h, greatly approaching the performance of the commercial Pt/C(-)//RuO2(+) electrolyzer and outperforming most other non-noble-based electrolyzers.

Hierarchical Nanoassembly of MoS2/Co9S8/Ni3S2/Ni as a Highly Efficient Electrocatalyst for Overall Water Splitting in a Wide pH Range

The design of low-cost yet high-efficiency electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) over a wide pH range is highly challenging. We now report a hierarchical co-assembly of interacting MoS₂ and Co₉S₈ nanosheets attached on Ni₃S₂ nanorod arrays which are supported on nickel foam (NF). This tiered structure endows high performance toward HER and OER over a very broad pH range. By adjusting the molar ratio of the Co:Mo precursors, we have created CoMoNiS-NF- xy composites ( x: y means Co:Mo molar ratios ranging from 5:1 to 1:3) with controllable morphology and composition. The three-dimensional composites have an abundance of active sites capable of universal pH catalytic HER and OER activity. The CoMoNiS-NF-31 demonstrates the best electrocatalytic activity, giving ultralow overpotentials (113, 103, and 117 mV for HER and 166, 228, and 405 mV for OER) to achieve a current density of 10 mA cm^-2 in alkaline, acidic, and neutral electrolytes, respectively. It also shows a remarkable balance between electrocatalytic activity and stability. Based on the distinguished catalytic performance of CoMoNiS-NF-31 toward HER and OER, we demonstrate a two-electrode electrolyzer performing water electrolysis over a wide pH range, with low cell voltages of 1.54, 1.45, and 1.80 V at 10 mA cm^-2 in alkaline, acidic, and neutral media, respectively. First-principles calculations suggest that the high OER activity arises from electron transfer from Co₉S₈ to MoS₂ at the interface, which alters the binding energies of adsorbed species and decreases overpotentials. Our results demonstrate that hierarchical metal sulfides can serve as highly efficient all-pH (pH = 0-14) electrocatalysts for overall water splitting.

Recent Advances in the Development of Water Oxidation Electrocatalysts at Mild pH

Developing anodic oxygen evolution reaction (OER) electrocatalysts with high catalytic activities is of great importance for effective water splitting. Compared with the water-oxidation electrocatalysts that are commonly utilized in alkaline conditions, the ones operating efficiently under neutral or near neutral conditions are more environmentally friendly with less corrosion issues. This review starts with a brief introduction of OER, the importance of OER in mild-pH media, as well as the fundamentals and performance parameters of OER electrocatalysts. Then, recent progress of the rational design of electrocatalysts for OER in mild-pH conditions is discussed. The chemical structures or components, synthetic approaches, and catalytic performances of the OER catalysts will be reviewed. Some interesting insights into the catalytic mechanism are also included and discussed. It concludes with a brief outlook on the possible remaining challenges and future trends of neutral or near-neutral OER electrocatalysts. It hopefully provides the readers with a distinct perspective of the history, present, and future of OER electrocatalysts at mild conditions.

Chlorine-doped α-Co(OH)2 hollow nano-dodecahedrons prepared by a ZIF-67 self-sacrificing template route and enhanced OER catalytic activity

A ZIF-67-self-sacrificing template strategy was designed for the synthesis of undoped/Cl-doped α-Co(OH)₂ hollow nano-dodecahedrons with enhanced OER performance.

Layered Ternary and Quaternary Transition Metal Chalcogenide Based Catalysts for Water Splitting

Water splitting plays an important role in the electrochemical and photoelectrochemical conversion of energy devices. Electrochemical water splitting by the hydrogen evolution reaction (HER) is a straightforward route to producing hydrogen (H2), which requires an efficient electrocatalyst to minimize energy consumption. Recent advances have created a rapid rise in new electrocatalysts, particularly those based on non-precious metals. In this review, we present a comprehensive overview of the recent developments of ternary and quaternary 6d-group transition metal chalcogenides (TMCs) based electrocatalysts for water splitting, especially for HER. Detailed discussion is organized from binary to quaternary TMCs including, surface engineering, heterostructures, chalcogen substitutions and hierarchically structural design in TMCs. Moreover, emphasis is placed on future research scope and important challenges facing these electrocatalysts for further development in their performance towards water splitting.

Controllable synthesis of NiO/Ni3S2 hybrid arrays as efficient electrocatalysts for water splitting

NiO/Ni₃S₂ affords a current density of 10 mA cm⁻² in 1.0 M KOH at a cell voltage of 1.59 V, i.e., comparable to the commercial 20 wt% IrO₂/C–40 wt% Pt/C couple (1.55 V at 10 mA cm⁻²).

Oxide/sulfide-based hybrid arrays as robust electrocatalysts for water splitting

NiCo₂O₄/Ni₃S₂ affords a current density of 10 mA cm⁻² in 1.0 M KOH at a cell voltage of 1.58 V, i.e., comparable to that of the commercial 20 wt% IrO₂/C–40 wt% Pt/C couple (1.52 V at 10 mA cm⁻²).