The electrochemical CO2 reduction reaction (CO2RR) is of great importance to tackle the rising CO2 concentration in the atmosphere. The CO2RR can be driven by renewable energy sources, producing precious chemicals and fuels, with the implementation of this process largely relying on the development of low‐cost and efficient electrocatalysts. Recently, a range of heterogeneous and potentially low‐cost single‐atom catalysts (SACs) containing non‐precious metals coordinated to earth‐abundant elements have emerged as promising candidates for the CO2RR. Unfortunately, the real catalytically active centers and the key factors that govern the catalytic performance of these SACs remain ambiguous. Here, this ambiguity is addressed by developing a fundamental understanding of the CO2RR‐to‐CO process on SACs, as CO accounts for the major product from CO2RR on SACs. The reaction mechanism, the rate‐determining steps, and the key factors that control the activity and selectivity are analyzed from both experimental and theoretical studies. Then, the synthesis, characterization, and the CO2RR performance of SACs are discussed. Finally, the challenges and future pathways are highlighted in the hope of guiding the design of the SACs to promote and understand the CO2RR on SACs.

Crystal phase control in layered transition metal dichalcogenides is central for exploiting their different electronic properties. Access to metastable crystal phases is limited as their direct synthesis is challenging, restricting the spectrum of reachable materials. Here, we demonstrate the solution phase synthesis of the metastable distorted octahedrally coordinated structure (1T' phase) of WSe 2 nanosheets. We design a kinetically-controlled regime of colloidal synthesis to enable the formation of the metastable phase. 1T' WSe 2 branched fewlayered nanosheets are produced in high yield and in a reproducible and controlled manner. The 1T' phase is fully convertible into the semiconducting 2H phase upon thermal annealing at 400°C. The 1T' WSe 2 nanosheets demonstrate a metallic nature exhibited by an enhanced electrocatalytic activity for hydrogen evolution reaction as compared to the 2H WSe 2 nanosheets and comparable to other 1T' phases. This synthesis design can potentially be extended to different materials providing direct access of metastable phases.

Enhanced photocatalytic degradation of methylene blue (MB) using graphitic carbon nitride/titanium dioxide (g-C3N4/TiO2) catalyst films has been demonstrated in this present work. The g-C3N4/TiO2 composites were prepared by directly heating the mixture of melamine and pre-synthesized TiO2 nanoparticles in Ar gas flow. The g-C3N4 contents in the g-C3N4/TiO2 composites were varied as 0, 20, 50 and 70 wt%. It was found that the visible-light-induced photocatalytic degradation of MB was remarkably increased upon coupling TiO2 with g-C3N4 and the best degradation performance of ~70% was obtained from 50 wt% g-C3N4 loading content. Results from UV-vis absorption study, Electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggest that the improved photoactivity is due to a decrease in band gap energy, an increased light absorption in visible light region and possibly an enhanced electron-hole separation efficiency as a result of effective interfacial electron transfer between TiO2 and g-C3N4 of the g-C3N4/TiO2 composite film. Based on the obtained results, the possible MB degradation mechanism is ascribed mainly to the generation of active species induced by the photogenerated electrons.

Tackling global climate change and the energy crisis requires novel approaches in clean energy generation and efficient manufacturing. [1] Hydrogen (H 2 ) is one of the most popular clean energy sources, providing the highest energy outputThe hydrogen evolution reaction (HER) is an emerging key technology to provide clean, renewable energy. Current state-of-the-art catalysts still rely on expensive and rare noble metals, however, the relatively cheap and abundant transition metal dichalcogenides (TMDs) have emerged as exceptionally promising alternatives. Early studies in developing TMD-based catalysts laid the groundwork in understanding the fundamental catalytically active sites of different TMD phases, enabling a toolbox of physical, chemical, and electronic engineering strategies to improve the HER catalytic activity of TMDs. This report focuses on recent progress in improving the catalytic properties of TMDs toward highly efficient production of H 2 . Combining theoretical and experimental considerations, a summary of the progress to date is provided and a pathway forward for viable hydrogen evolution from TMD driven catalysis is concluded.

Thermoelectrochemical cells (thermocells) designed for harvesting human body heat can provide constant power output for wearable electronics, supplementing state‐of‐the‐art flexible power storage and conversion solutions. However, a systematic investigation into the optimization of wearable thermocells is lacking, especially with regard to device design, n‐type electrolytes, and electrode/electrolyte integration. Here, a n‐type gel electrolyte: polyvinyl alcohol‐FeCl2/3 with outstanding flexibility and elasticity and exceptional electrolyte/electrode integration into a 3D porous poly(3,4‐ethylenedioxythiophene)/polystyrenesulfonate (PEDOT/PSS) electrode, is produced via an in situ chemical crosslinking method. The integrated n‐type cell shows excellent seebeck coefficients (0.85 mV K−1) and output current density (1.74 A m−2 K−1) that are comparable with an optimized p‐type cell consisting of a carboxymethylcellulose‐K3/4Fe(CN)6 electrolyte with a 3D PEDOT/PSS‐edge functionalized graphene/carbon nanotube electrode (−1.22 mV K−1 and 1.85 A m−2 K−1). The equivalent performance of the n‐type and p‐type cells enables the effective series connection of up to 18 pairs of p–n cells that combines to give an output voltage of 0.34 V (∆T = 10 K). This in‐series device is fabricated into a proof‐of‐concept watch strap, which can harvest body heat, charge supercapacitor (up to 470 mF) as well as illuminate a green light emitting diode, demonstrating the practical applications.

The solar-assisted oxidation of water is an essential half reaction for achieving a complete cycle of water splitting. nanosheets results in a 10-fold increase in incident-photon-to-current-efficiency compared to the individual constituents. This proves that charge carrier lifetime is tailorable in atomically thin crystals by creating heterojunctions of different compositions and architectures. Our results suggest that the MoS 2 and WS 2 nanosheets and their bulk heterojunction blend are interesting photocatalytic systems for water oxidation, which can be coupled with different reduction processes for solar-fuel production.

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Multiwalled CNT entangled networks integrated into a highly conducting carbon layer can be grown on a range of substrates including glassy carbon and metal foils. A continuous flexible CNT electrode with high surface area and conductivity is produced, with a stable battery capacity of 572 mAh g–1. This discovery provides a direct route for the generation of large‐scale flexible CNT electrode materials.