• Energy Research

AbstractMonocrystalline ZnO nanorods (NRs) with high donor concentration are electrochemically deposited on highly conductive reduced graphene oxide (rGO) films on quartz. The film thickness, optical transmittance, sheet resistance, and roughness of rGO films are systematically studied. The obtained ZnO NRs on rGO films are characterized by X‐ray diffraction, transmission electron microscopy, photoluminescence, and Raman spectra. As a proof‐of‐concept application, the obtained ZnO NRs on rGO are used to fabricate inorganic–organic hybrid solar cells with layered structure of quartz/rGO/ZnO NR/poly(3‐hexylthiophene)/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (P3HT/PEDOT:PSS)/Au. The observed power conversion efficiency (PCE, η), ≈ 0.31%, is higher than that reported in previous solar cells by using graphene films as electrodes. These results clearly demonstrate that rGO films with a higher conductivity have a smaller work function and show a better performance in the fabricated solar cells.

Global energy and environmental crises are among the most pressing challenges facing humankind. To overcome these challenges, recent years have seen an upsurge of interest in the development and production of renewable chemical fuels as alternatives to the nonrenewable and high-polluting fossil fuels. Photocatalysis, photoelectrocatalysis, and electrocatalysis provide promising avenues for sustainable energy conversion. Single- and dual-component catalytic systems based on nanomaterials have been intensively studied for decades, but their intrinsic weaknesses hamper their practical applications. Multicomponent nanomaterial-based systems, consisting of three or more components with at least one component in the nanoscale, have recently emerged. The multiple components are integrated together to create synergistic effects and hence overcome the limitation for outperformance. Such higher-efficiency systems based on nanomaterials will potentially bring an additional benefit in balance-of-system costs if they exclude the use of noble metals, considering the expense and sustainability. It is therefore timely to review the research in this field, providing guidance in the development of noble-metal-free multicomponent nanointegration for sustainable energy conversion. In this work, we first recall the fundamentals of catalysis by nanomaterials, multicomponent nanointegration, and reactor configuration for water splitting, CO2 reduction, and N2 reduction. We then systematically review and discuss recent advances in multicomponent-based photocatalytic, photoelectrochemical, and electrochemical systems based on nanomaterials. On the basis of these systems, we further laterally evaluate different multicomponent integration strategies and highlight their impacts on catalytic activity, performance stability, and product selectivity. Finally, we provide conclusions and future prospects for multicomponent nanointegration. This work offers comprehensive insights into the development of cost-competitive multicomponent nanomaterial-based systems for sustainable energy-conversion technologies and assists researchers working toward addressing the global challenges in energy and the environment.

Membrane modification may obstruct metal-ion mass flux, increasing battery overpotential and reducing performance. Balancing shuttle effect of separator-crossing species and minimizing overpotential-induced energy loss is crucial.

The significant phase change between gaseous and crystalline oxygen deteriorates the performance of lithium–air batteries. Here the authors report a battery with a cathode consisting of Li2O and Co3O4 nanocomposites, which displays stable cyclability and high energy density, without involving any gas evolution.

The chemically reduced graphene oxide (rGO) was transferred onto polyethylene terephthalate (PET) substrates and then used as transparent and conductive electrodes for flexible organic photovoltaic (OPV) devices. The performance of the OPV devices mainly depends on the charge transport efficiency through rGO electrodes when the optical transmittance of rGO is above 65%. However, if the transmittance of rGO is less than 65%, the performance of the OPV device is dominated by the light transmission efficiency, that is, the transparency of rGO films. After the tensile strain (∼2.9%) was applied on the fabricated OPV device, it can sustain a thousand cycles of bending. Our work demonstrates the highly flexible property of rGO films, which provide the potential applications in flexible optoelectronics.

AbstractThe structure–property engineering of phase‐based materials for redox‐reactive energy conversion and environmental decontamination nanosystems, which are crucial for achieving feasible and sustainable energy and environment treatment technology, is discussed. An exhaustive overview of redox reaction processes, including electrocatalysis, photocatalysis, and photoelectrocatalysis, is given. Through examples of applications of these redox reactions, how structural phase engineering (SPE) strategies can influence the catalytic activity, selectivity, and stability is constructively reviewed and discussed. As observed, to date, much progress has been made in SPE to improve catalytic redox reactions. However, a number of highly intriguing, unresolved issues remain to be discussed, including solar photon‐to‐exciton conversion efficiency, exciton dissociation into active reductive/oxidative electrons/holes, dual‐ and multiphase junctions, selective adsorption/desorption, performance stability, sustainability, etc. To conclude, key challenges and prospects with SPE‐assisted redox reaction systems are highlighted, where further development for the advanced engineering of phase‐based materials will accelerate the sustainable (active, reliable, and scalable) production of valuable chemicals and energy, as well as facilitate environmental treatment.

Hydrogen gas as a clean energy source, it is a promising alternative to fossil fuels. Therefore, people are actively seeking effective ways to produce hydrogen to cope with the imminent global energy shortage. However, the current production of hydrogen relies on the catalytic reforming of fossil fuels, inducing inevitable environmental pollution. Alternatively, photocatalysis for produce hydrogen gas from reforming alcohols is a promising approach. Especially, other value‐added hydrocarbon products, such as acetone, acetaldehyde, acetic acid, etc., can also be produced during the photoreforming process of alcohols. Meanwhile, reducing the production of COx, making it an environmentally friendly conversion process. Outstandingly, TiO2 and its derivative are excellent photocatalysts. Among them, TiO2 cocatalyzed with noble metal can easily increase the H2 evolution rate to the mmol g−1 h−1 scale. Among the light alcohols isopropyl alcohol has fewer side reactions, methanol and ethanol have higher reaction rate, but they require to reduce the by‐product COx. In this review, the recent developments in this field are summarized; various studies regarding H2 evolution rate, illumination condition, quantum efficiency, etc., are compared; and the development prospects of this field, with the hope of sparking widespread research interest, are proposed.

Hollow hierarchical spheres self-organized from the ultrathin nanosheets of α-Fe2O3 were prepared by a simple process. These ultrathin nanosheet subunits possess an average thickness of around 3.5 nm and show preferential exposure of (110) facets. Their Li ion storage and visible-light photocatalytic water oxidation performance are tested. Such hierarchical nanostructures show high Li storage properties with good cycling stability and excellent rate capabilities. The water oxidation catalytic activity is 70 μmol h−1 g−1 for O2 evolution under visible light irradiation and can be maintained for 15 hours. The structural features of these α-Fe2O3 nanocrystals are considered to be important to lead to the attractive properties in both Li storage and photocatalytic water oxidation, e.g. hollow interior, ultrathin thickness and largely exposed active facets.