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CuBi2O4 is a promising p-type semiconductor material with a theoretical maximum current density of about 19.7 mA cm‒2. Although CuBi2O4 has a very high theoretical photocurrent, its poor charge transmission efficiency makes its actual photocurrent far less than its theoretical values. Herein, an in situ modification method is adopted to prepare a photocathode material with Ag as conductive channels. A metal–organic coating method is used to introduce Ag conductive channels, promoting the charge transmission between grains. Ag particles play the role of electrical connection, and improve the separation and transmission of carriers, so as to obtain enhanced photocurrent density. In situ formed Ag conductive channels significantly enhanced the PEC performance of CuBi2O4 photocathodes. [ABSTRACT FROM AUTHOR]

Developing efficient and low-cost electrocatalysts for hydrogen evolution reaction (HER) is important for hydrogen fuel production. In this study, we synthesized two different types of CoS 2 under low sulfur (LS) and high sulfur concentration (HS) conditions. Structural analysis results show that CoS impurity phase forms easily when the concentration of sulfur is low, while at high sulfur concentration the growth of CoS impurity phase is inhibited and leads to phase-pure CoS 2. Electrochemical investigation of HER performance reveals that the onset potential of CoS 2 (HS) electrode (ca. − 0.11 V vs. the reversible hydrogen electrode, RHE) is 30 mV anodic of the CoS 2 (LS) one (ca. − 0.14 V vs. RHE). At a specific current density of 10 mA cm−2 the required overpotential on CoS 2 (HS) electrode is only 163 mV, which is 40 mV less than the CoS 2 (LS) electrode. Electrochemical impedance spectroscopy (EIS) data further demonstrate that the charge transfer rate of CoS 2 (HS) electrode is faster than that of CoS 2 (LS) electrode towards HER. • CoS 2 electrocatalysts with two different nanostructures and stoichiometries are produced. • Sulfur concentration plays a key role in the synthesis of CoS 2. • High sulfur concentration is conducive to reducing the formation of sulfur vacancies. [ABSTRACT FROM AUTHOR]

With the dramatic increase in the application of modern office equipment, such as laser printers and photocopiers, large amounts of waste toner powder are used and discarded, ending up in landfills around the world. As waste toner powder contains hazardous compounds that can seriously endanger both the environment and human health, it is urgent to deal with waste toner powder and convert it into high value-added products. In this work, we report, for the first time, visible-light-driven hydrogen production with waste toner activated by cheap Ni species (waste toner@Ni-species) as the photocatalyst. The Ni species adhered to the waste toner through in situ photoreduction, without sophisticated equipment. It is found that the Ni species were composed of metallic Ni and oxidized Ni, which worked in synergy to remarkably enhance the photocatalytic activity of the waste toner. Activated by the Ni species, the hydrogen evolution rate of the waste toner was accelerated by up to 62 times, and the apparent quantum efficiencies (AQEs) of the waste toner were boosted by up to 64 times. In addition, the waste toner@Ni-species exhibited a higher charge separation efficiency, faster interfacial charge transfer rate and ∼200 mV lower barrier for proton reduction than those of the pristine waste toner. In addition to these merits, the waste toner@Ni-species could be separated conveniently from the aqueous system using magnetic attraction, as the saturation magnetization and residual magnetism of the waste toner were improved with the assembly of the Ni species. The approach shown here indicates a simple and promising way to deal with waste toner by converting it to a cost-effective photocatalyst for producing clean energy. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting is a promising approach to generating hydrogen from water. In order to enhance water splitting efficiency, it is essential to promote gas revolution from catalysts surface, reduce the over-potential of oxygen evolution (OER), and inhibit the production of the hydrogen peroxide by-product. To realize them, in this work, we take a cue from nature to promote water splitting activity of hollow porous Fe 3 O 4 microspheres (M−Fe 3 O 4) with the aids of hemoglobin. Hemoglobin monolayer was self-assembled on the surface of M−Fe 3 O 4 catalysts. It transported newly-generated oxygen molecules away from catalysts surface and exhibited chiral-induced spin selectivity ( CISS ) effect during OER reaction. Owing to the "helping hand" of hemoglobin, the OER onset potential of hollow porous Fe 3 O 4 microspheres reduced by 100 mV and the current density was enhanced 2 folds. The results indicate a new strategy for designing earth-abundant catalysts which combine the merits of oxygen transferring and CISS effect for electrocatalytic water splitting. Image 1 • Self-assembling hemoglobin monolayer on the surface of hollow Fe 3 O 4 microspheres. • Timely moving newly-generated oxygen molecules away from catalysts by HB layer. • Suppressing H 2 O 2 production by HB induced chiral-induced spin selectivity effect. [ABSTRACT FROM AUTHOR]