Rapid Fabrication of Ni/NiO@CoFe Layered Double Hydroxide Hierarchical Nanostructures by Femtosecond Laser Ablation and Electrodeposition for Efficient Overall Water Splitting

Polyaniline Induced Trivalent Ni in Laser-Fabricated Nickel Oxides for Efficient Oxygen Evolution Reaction

Although it is generally acknowledged that transition metals at high oxidation states represent superior oxygen evolution reaction (OER) activity, the preparation and stability of such a high-valence state are still a challenge, which requires relatively harsh reaction conditions and is unstable under ambient conditions. Herein, we report the formation of trivalent nickel (Ni3+) in laser-fabricated nickel oxides induced by polyaniline (PANI) under electrochemical activation via a significant charge transfer between Ni and N, as confirmed by X-ray photoelectron spectroscopy and density functional theory calculations. Thereafter, the presence of Ni3+ and the improved conductivity by PANI effectively increase the electrochemical OER activity of the samples together with excellent long-term stability. This work provides new insights for the rational manufacture of high-valence metal for electrochemical reactions.

Facile synthesis of FeNi alloy-supported N-doped Mo2C hollow nanospheres for the oxygen evolution reaction

The rapid depletion of fossil fuels results in significant environmental pollution. Consequently, researching environmentally friendly and cost-effective electrocatalysts with exceptional oxygen evolution reaction (OER) capabilities holds immense importance in enhancing the efficient utilization of resources. In this paper, a straightforward and cost-effective method was employed to produce Fe-Ni alloy-supported N-doped carbon hollow nanospheres (FeNi/Mo2C/NC) using self-assembled molybdenum dopamine spheres (Mo-PDA-HS) as a substrate. The inclusion of iron and nickel addressed the issue of aggregation and collapse in Mo-PDA-HS nanostructures at high temperatures, while adjusting the electronic structure of the composites to achieve efficient OER activity. The composite displayed a low overpotential (η10 mA = 304 mV) and a minimal Tafel slope (41.8 mV/dec-1). This study introduces a simple strategy for constructing structurally robust and non-aggregating Mo2C nanostructures, along with a direct method for designing cost-effective and high-performance catalysts for OER.

Fast and Deep Reconstruction of Coprecipitated Fe Phosphates on Nickel Foams for an Alkaline Oxygen Evolution Reaction

Although there is a general consensus that the electrocatalysts will undergo reconstruction to generate (oxy)hydroxides as real active sites during the electrochemical oxygen evolution reaction (OER), the understanding of this process is still far from satisfactory. In particular, the reconstruction process of most of these electrocatalysts is either slow or occurs only on the surface, which thus restrains the OER performance of the electrocatalysts. Herein, we reveal a fast and deep reconstruction of the coprecipitated Fe phosphates on nickel foam, via in situ Raman spectroscopy together with electron microscopy, X-ray photoelectron spectroscopy, and electrochemical tests. The generated NiFe (oxy)hydroxide nanosheets after reconstruction behave as the real active sites for the OER in the alkaline condition, with a low overpotential and excellent durability. The present work provides deep insights on the reconstruction dynamics of OER electrocatalysts.

A comparative study of the effects of different TiO2 supports toward CO2 electrochemical reduction on CuO/TiO2 electrode

CuO-based electrodes possess vast potential in the field of CO₂ electrochemical reduction. Meantime, TiO₂ supports show the advantages of being non-toxic, low-cost and having high chemical stability, which render it an ideal electrocatalytic support with CuO. However, different morphologies and structures of TiO₂ supports can be obtained through various methods, leading to the discrepant electrocatalytic properties of CuO/TiO₂. In this paper, three supports, named dense TiO₂, TiO₂ nanotube and TiO₂ nanofiber, were applied to synthesize CuO/TiO₂ electrodes by thermal decomposition, and the performances of the electrocatalysts were studied. Results show that the main product of the three electrocatalysts was ethanol, but the electrochemical efficiency and reaction characteristics are obviously different. The liquid product of CuO/Dense TiO₂ is pure ethanol, however, the current efficiency is rather low owing to the higher resistance of the TiO₂ film. CuO/TiO₂ nanotube shows high conductivity and ethanol can be synthesized at low overpotential with high current efficiency, but the gas products cannot be restricted. CuO/TiO₂ nanofiber has a larger specific surface area and more active sites, which is beneficial for CO₂ reduction, and the hydrogen evolution reaction can be evidently restricted. The yield of ethanol reaches up to 6.4 μmol cm⁻² at −1.1 V (vs. SCE) after 5 h.

Electrocatalytic reduction of CO₂ on three different morphologies of CuO/TiO₂.

Container-Sized CO2 to Methane: Design, Construction and Catalytic Tests Using Raw Biogas to Biomethane

Direct catalytic methanation of CO2 (from CO2/CH4 biogas mixture) to produce biomethane was conducted in a pilot demonstration plant. In the demonstration project (MeGa-StoRE), a biogas desulfurization process and thermochemical methanation of biogas using hydrogen produced by water electrolysis were carried out at a fully operational biogas plant in Denmark. The main objective of this part of the project was to design and develop a reactor system for catalytic conversion of CO2 in biogas to methane and feed biomethane directly to the existing natural gas grid. A process was developed in a portable container with a 10 Nm3/h of biogas conversion capacity. A test campaign was run at a biogas plant for more than 6 months, and long-time operation revealed a stable steady-state conversion of more than 90% CO2 conversion to methane. A detailed catalytic study was performed to investigate the high activity and stability of the applied catalyst.

Co(OH)2 Nanosheets Supported on Laser Ablated Cu Foam: An Efficient Oxygen Evolution Reaction Electrocatalyst

Highly efficient and low-cost non-noble metal based electrocatalysts for oxygen evolution reaction (OER) have attracted more and more attention in recent years. However, the current research has been focused on the construction of novel OER electrocatalysts themselves, little attention has been paid to the modification of the substrates. In this work, a different strategy is proposed via laser ablation to fabricate the Cu foams with rich micro/nano-structures as OER substrates. Later, the precipitation conversion method was utilized to grow cobalt hydroxide on the laser fabricated Cu foams. The as-produced Cu/Cu oxides/Co(OH)₂ electrocatalysts exhibit high OER activity in 1 M KOH, requiring an overpotential of only 259 mV at a current density of 50 mA cm^-2 with excellent mild-term durability. The improved catalytic performance of the prepared samples can be attributed to the increased surface area, rich active sites, and the superhydrophilicity of the laser produced micro/nano-structures.

Adjustable anchoring of Ni/Co cations by oxygen-containing functional groups on functionalized graphite paper and accelerated mass/electron transfer for overall water splitting

NCS–NCO/FGP_0.44 with a cellular network of porous nanosheets and close-contact heterointerface reveals accelerated interfacial mass/electron transportation for overall water splitting.

In Situ Integration of ReS2/Ni3S2 p-n Heterostructure for Enhanced Photoelectrocatalytic Performance

The excellent light absorption, low electron-hole recombination rate, and fast reaction kinetics of photogenerated charges are urgently needed for photoelectrochemical (PEC) water splitting. Herein, a novel p-n heterostructure photoelectrode (ReS₂/Ni₃S₂) is constructed via a one-step hydrothermal method, which shows remarkable HER activity under illumination such as a low overpotential (η₁₀) of 106 mV, high IPCE of 10-15%, and good stability. High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) reveal that the intimate interface and strong electron interaction between ReS₂ and Ni₃S₂ can enhance the light adsorption and provide abundant active sites. The transient absorption (TA) spectroscopy and impedance spectroscopy analyses (EIS) demonstrate the prolonged carrier lifetime and fast charge transfer. All of these are responsible for the improvement of reaction kinetics. This work provides a brand new avenue to explore efficient photoelectrocatalysts for water splitting.