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Seawater electrolysis is a promising technology for the production of hydrogen energy and seawater desalination. To produce hydrogen energy through seawater electrolysis, highly active electrocatalysts for the oxygen evolution reaction (OER) are required. Here, we report the development of a Ni-doped FeOOH anode for high-efficiency anion exchange membrane alkaline seawater electrolysis. The Ni-doped FeOOH anode showed an overpotential of only 301 mV in half-cell tests, reaching a current density of 100 mA cm−2 in 1.0 M KOH + seawater. An anion exchange membrane electrolyzer catalyzed by Ni-doped FeOOH exhibited a current density of 729 mA cm−2 in 1.0 M KOH + seawater with an energy conversion efficiency of 76.35%. Compared to the reported AEM electrolyzer operated in 1.0 M KOH, our AEM electrolyzer catalyzed with Ni-doped FeOOH operated in 1.0 M KOH + seawater exhibited higher performance.

The application of electrocatalysts with high activity to a practical water electrolysis cell is a crucial challenge for the production of pure hydrogen and commercialization of the water electrolyzer. Herein, a nanosized Cu0.5Co2.5O4 catalyst synthesized by co-precipitation by adjusting pH is applied to the anion exchange membrane water electrolysis (AEMWE) cell as an anode, which is demonstrated to have higher efficiency and stability than noble metal-based anodes. The composition (Cu/Co) and morphology of Cu0.5Co2.5O4 change as the pH increases and then nanoparticles are formed at pH 11, where oxygen vacancies are formed by the etching of Cu. In the density functional theory study, the electronic structure of Co modified by Cu in the Co3O4 lattice leads to an optimal adsorption strength, resulting in a free energy diagram in which the potential of Cu0.5Co2.5O4 (1.756 V vs. reversible hydrogen electrode, RHE) is more thermodynamically favorable than that of Co3O4 (1.951 V vs. RHE). The Cu0.5Co2.5O4 catalyst has a recorded overpotential of 285 mV at 10 mA cm−2 in 1 M KOH. Furthermore, the AEMWE cell using Cu0.5Co2.5O4 as an anode exhibited a current density of 1.3 A cm−2 at 1.8 V, which is the highest performance among the reported papers and maintains around 80% energy conversion efficiency for 100 hours.

The selective and efficient electrocatalytic transformation of carbon dioxide (CO2) to multicarbon alcohols (e.g., C2H5OH and C3H7OH) is a challenge in renewable and sustainable energy research. Herein, a series of hybrid catalysts consisting of Cu nanoparticles supported on N-doped porous carbon (Cu/NPC) were prepared. It was demonstrated that the selectivity for C2H5OH or C3H7OH could be tuned by introducing N-doped porous carbon materials as cocatalysts with different pyridinic N contents, which could in situ produce a reactive CO intermediate from CO2. By varying the pyridinic N content, highly selective production of multicarbon alcohols was achieved using the Cu/NPC hybrid catalysts with a high faradaic efficiency for one pot production of multicarbon alcohols up to 73.3% at −1.05 V (vs. RHE). The faradaic efficiency for C2H5OH and C3H7OH was 64.6% and 8.7%, respectively. The pyridinic N species were likely the CO-producing sites and together with Cu catalytic sites acted cooperatively to produce C2H5OH and C3H7OH via a two-site mechanism for efficient CO2 reduction to multicarbon alcohols. These findings provide novel guidance for the rational design of electrocatalysts and for tuning the catalytic activity and selectivity for multicarbon alcohol production from CO2.

Recently, copper iodide (CuI) has been considered as a promising inorganic p-type semiconductor material. Although significant progress using CuI has been made in materials and device applications for solar cells and thin-film transistors (TFTs), little consideration has been given to the vacancy formation mechanisms and their effect on the device performance. In this work, high performance electrolyte-gated TFTs were fabricated using CuI semiconductors with different vacancy states and the origin of the threshold voltage (Vth) shift of devices in terms of vacancy species and concentration were studied. The CuI films were fabricated via a simple solution process followed by thermal annealing at low temperature (55 °C). The vacancy species and concentration in the CuI semiconductor were regulated by changing the annealing conditions as well as by introducing a dopant material. Photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) analysis were conducted to demonstrate the correlation between the electrical properties of TFTs and the vacancy states in the CuI specimens. The CuI-TFTs exhibited typical enhancement mode operation of the p-channel transistor, with sub-1 V operation voltage, ON/OFF ratio of ∼103, and high hole mobility in the range of 10–60 cm2 V−1 s−1. Experimental results revealed that Cu vacancy (VCu) play the role of inducing hole carriers, hence, TFT with VCu-rich CuI exhibited increased carrier concentration and positively shifted Vth of 0.14 V. However, iodine vacancy (VI) in CuI captures hole carriers, decreasing the concentration of charge carriers (holes), resulting to a negative Vth of −0.19 V. The TFT mobility was also affected by the vacancy concentration, owing to the carrier scattering effect. For instance, the I-rich (or VCu-rich) CuI exhibited decreased TFT mobility (14.70 cm2 V−1 s−1) due to the high carrier concentration (1019 cm−3) and their scattering effect.

Single-crystalline CoFe alloy nanoparticles encapsulated in nitrogen-doped carbon nanotubes (CoFe@N–C) were synthesized through a simple heat-treatment in an N2 environment. CoFe@N–C effectively catalyzed the overall water splitting in alkaline media. Specifically, the as-synthesized CoFe@N–C exhibited excellent activity towards the oxygen evolution reaction (OER) with a low overpotential of 292 mV at 10 mA cm−2 and the hydrogen evolution reaction (HER) with a low overpotential of 110 mV at 10 mA cm−2. The good electrocatalytic properties may be attributed to the synergistic electronic coupling between single-crystalline CoFe and highly conductive N-doped CNTs and the enrichment of active sites. Additionally, CoFe@N–C showed excellent stability and durability with no observable deviation in the overpotential for the OER and HER after 1000 cycles of cyclic voltammetry (CV).

The immobilization of Cyt. c (cytochrome c) on C60 (fullerene) nanohybrid TiO2 (titanium dioxide) gel films assembled with C60, Ti(O–nBu)4 and Cyt. c was realized by a surface sol–gel process. Interestingly, C60 was used without any surface modification of the film formation and exhibited good electrochemical performance. Additionally, the surface morphologies of the TiO2 and TiO2/C60 nanocomposite thin films showed remarkable uniformity over a wide area, however, the surface morphology depends on the deposition of Cyt. c, which densely covers the surface with adsorbed Cyt. c molecules. The cyclic voltammetry of the outer-most fullerene films revealed high stability, as well as, a pair of current peaks characteristic of a weak redox system with anodic and cathodic peak potentials at 0.262 V and 0.137 V. The electrochemical properties of thin films can be attributed to the redox system of the C60 layer deposited on the TiO2 gel layer. A pair of well-defined quasi-reversible redox peaks generated by Cyt. c are easily achieved because of the efficient assembly on the C60-modified electrode. In this work, we suggest the efficient introduction of C60 into a TiO2 gel matrix, evaluating the electrochemical characteristics of Cyt. c assembly.

High metal loaded (60 wt%) binary PdM (M = Ru, Sn, Ir) catalysts were synthesized on reduced graphene oxide (RGO) using the borohydride reduction method, and they were used for the electro-oxidation of simple alcohols, such as methanol, ethanol, and 1-propanol, in alkaline media. Cyclic voltammetry (CV) tests indicated that the Pd-based binary systems could improve electrochemical activities significantly compared to the monometallic Pd/RGO catalyst. Among the prepared catalysts, addition of Ru to Pd (PdRu/RGO) resulted in remarkably improved electrocatalytic activity in terms of larger peak current densities and lower onset potential in all electro-oxidation cases with methanol, ethanol, and 1-propanol. CO-stripping tests also revealed that the onset and peak potentials for the CO oxidation appear to decrease by the addition of Ru to Pd/RGO, indicating that the electro-oxidation of CO can take place more efficiently on the PdRu/RGO catalyst with the assistance of easily formed hydroxyl groups. Such an improvement of electrocatalytic performance can be ascribed to structural and chemical modifications of the Pd catalysts. Physicochemical properties of the PdM/RGO catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS).

Reduced graphene oxide (RGO)-supported bimetallic Pd–Pt nanostructures with core–shell Pd@Pt (Pd@Pt/RGO) and alloyed PdPt (PdPt/RGO) were prepared by a one-pot reduction approach using L-ascorbic acid for the reduction of both the metal precursors and the graphene oxide supports. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), and Raman spectroscopy revealed that the three-dimensionally shaped Pd–Pt nanostructures were uniformly deposited onto the reduced graphene oxide surface. The RGO-supported core–shell Pd@Pt and alloyed PdPt catalysts were confirmed and investigated by high-angle annular dark-field scanning TEM (HADDF-STEM) with energy-dispersive X-ray spectroscopy (EDX) in addition to X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and cyclic voltammetry (CV). With the synergetic effects of the binary Pd–Pt system and the RGO support, these catalysts exhibited considerably enhanced catalytic activities and stabilities for the oxidation of methanol in an alkaline solution compared to monometallic Pt/RGO and commercially available carbon-supported Pt (Pt/C) catalysts. The star-shaped core–shell Pd@Pt/RGO catalysts exhibited the greatest improvement in electrocatalytic performance in terms of current density, onset potential, stability, and the charge transfer rate.

N4-chelate macrocycles comprise the foundation for non-precious metal oxygen reduction reaction (ORR) catalyst research, where the main electrochemical process occurs in polymer electrolyte membrane (PEM) fuel cells. Although iron–nitrogen–carbon (M–N–C) complexes are known to be the most active non-precious ORR catalysts to date, a fundamental understanding of the ORR mechanisms of these materials is still in its nascent stage and needs further investigation. In this work, ab initio density functional theory (DFT) calculations have been applied to unveil the underlying principles for the electrocatalytic activity and structural stability of Fe–N4 chelates exposed to acidic media. Therefore, we compared the electronic structures of ferrous phthalocyanine (Fe-Pc) and an in-house developed Fe-Pc modified with diphenylphenthioether substituent species (Fe-SPc). The results of these DFT simulations directly correlate with the results of the half-cell ORR activity and stability electrochemical testing in 0.1 M HClO4. The results indicate that the relative energetic position of the dz2-orbital with respect to the Fermi level can induce an Fe redox couple potential shift and modulate the catalytic activity towards the ORR. Furthermore, our combined DFT calculations and empirical observations highlight that the relative position of the dz2-orbital can be controlled by the incorporation of functional groups, resulting in the ability to tune the ORR activity of these complexes. Structural stability of the materials, as predicted by the DFT-calculated cohesive energies of Fe and FeO, can also be readily tuned by modulating Fe-Pc with the substituent species. This study, coupling rigorous experimental observations with DFT investigations, thereby provides a fundamental insight that can aid in the design of future generations of non-precious ORR catalysts with improved activity and stability.

This paper reports a novel and efficient strategy for fabricating sub-100 nm metal ring arrays using a simple printing process. Vertically aligned carbon nanotubes that are supported by hexagonally ordered channels of alumina matrices are used as a stamp to print nanoscale ring patterns, which is a very unique stamping platform that has never been reported. Using this strategy, uniform nanoring patterns of various metals can be directly printed onto a wide range of substrate surfaces under ambient conditions. Significantly, the size and interval of the printed nanorings can be systematically tuned by controlling the ring-shaped tip dimensions of the pristine stamps. An advanced example of these printable nanoscale metal ring arrays is explicitly embodied in this work by investigation of the plasmon resonances of metal nanorings with different sizes and intervals.

This work reports the direct growth of hollow one-dimensional nanostructure arrays on conducting substrates for use as efficient electrodes in Li-ion batteries. The C-coated hollow SnO2 pillar array structures can be prepared by template-directed synthesis, selective wet etching, and a carbonization route. The well-oriented ZnO nanorod arrays, which are grown on titanium substrates, are used as a sacrificial template for the deposition of SnO2 layers through a simple hydrothermal process. The ZnO portions are selectively removed by wet etching, producing hollow SnO2 arrays that are consecutively covered with carbon layers via the carbonization of glucose. The lithium storage performance of the synthesized C-coated hollow SnO2 pillar array structures is demonstrated by applying them directly to a working electrode without additive materials. The standing pillar array electrode, consisting of C-coated hollow SnO2, exhibits an excellent discharge capacity of ca. 1251.9 mA h g−1 on the first cycle, and it also shows promising cyclability, rate capability, and coulombic efficiency, indicating that C-coated hollow SnO2 arrays fabricated on the current collector can be powerful candidates for a highly stable lithium storage electrode platform.