Polymer solid-state electrolytes (PSSEs) are promising for solving the safety problem of Lithium (Li) metal batteries (LMBs). However, PSSEs with low modulus in nature are prone to be penetrated by lithium dendrites, resulting in short circuit of LMBs. Here, we design and prepare piezoelectric BaTiO3 doped polyacrylonitrile (PAN@BTO) quasi-solid-state electrolytes (PQSSEs) by electrostatic spinning method to suppress dendritic growth. The piezoelectric polymer electrolytes are squeezed by nucleation and growth processes of Li dendrites, which can generate a piezoelectric electric field to regulate the deposition of Li+ ions and eliminate lithium bud. Consequently, piezoelectric PAN@BTO PQSSEs enables highly stable Li plating/stripping cycling for over 2 000 h at 0.15 mA/cm2 at room temperature (RT, 25 degrees C). Also, LiFePO4|PAN@BTO|Li full cells demonstrate excellent cycle performance (136.9 mA center dot h/g and 78% retention after 600 cycles at 0.5 C) at RT. Moreover, LiFePO4|PAN@BTO|Li battery show extremely high safety and can still work normally under high-speed impact (2 Hz, -30 kPa). We construct an in-situ cell monitoring system and disclose that the mechanism of suppressed lithium dendrite is originated from the generation of opposite piezoelectric potential and the feedback speed of intermittent piezoelectric potential signals is extremely fast. (c) 2023 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The rutile phase IrO2, as a promising catalyst for oxygen evolution reaction (OER), still falls short of satisfactory activity. Here, a novel 1D monoclinic phase iridium-ruthenium oxide solid solution (m-IrxRu1-xO2) is reported. For m-IrxRu1-xO2 with different metal proportions, the optimal m-Ir0.91Ru0.09O2-delta catalyst exhibits excellent OER activity under acidic conditions with an overpotential of 180 mV at 10 mA cm(-2). As an anode catalyst in a proton exchange membrane electrolyzer, m-Ir0.91Ru0.09O2-delta with a low catalyst loading (0.1 mg cm(-2)) can operate approximate to 256 h at 1.8 V with a high current density over 900 mA cm(-2) at room temperature. Such a satisfied stability may have originated from the specific morphology and crystal structure, which is confirmed by the transient potential scanning test. Density functional theory calculations show that the Ru in the m-IrxRu1-xO2 facilitates decreasing the OER overpotentials due to the electron transfer from Ru to Ir.

The in -situ electrochemically reconstructed Cu 2 O/CeO 2 from CuO/CeO 2 has been demonstrated to be effective for electrocatalytic carbon dioxide reduction, delivering a high selectivity, activity, and stability for producing CH 4 .

Addressing the sluggish kinetics in the alkaline hydrogen oxidation reaction (HOR) is a pivotal yet challenging step toward the commercialization of anion-exchange membrane fuel cells (AEMFCs). Here, we have successfully immobilized indium (In) atoms in an orderly fashion into platinum (Pt) nanoparticles supported by reduced graphene oxide (denoted as O-Pt3In/rGO), significantly enhancing alkaline HOR kinetics. We have revealed that the ordered atomic matrix enables uniform and optimized hydrogen binding energy (HBE), hydroxyl binding energy (OHBE), and carbon monoxide binding energy (COBE) across the catalyst. With a mass activity of 2.3066 A mg-1 at an overpotential of 50 mV, over 10 times greater than that of Pt/C, the catalyst also demonstrates admirable CO resistance and stability. Importantly, the AEMFC implementing this catalyst as the anode catalyst has achieved an impressive power output compared to Pt/C. This work not only highlights the significance of constructing ordered oxophilic sites for alkaline HOR but also sheds light on the design of well-structured catalysts for energy conversion.

The coupled green energy and chemical production by photocatalysis represents a promising sustainable pathway, which poses great challenges for the multifunction integration of catalytic systems. Here we show a promising green photocatalyst design using Cu-ZnIn2S4 nanosheets and carbon dots as building units, which enables the integration of reaction, mass transfer, and separation functions in the nano-space, mimicking a nanoreactor. This function integration results in great activity promotion for benzyl alcohol oxidation coupled H-2 production, with H-2/benzaldehyde production rates of 45.95/46.47mmolg(-1)h(-1), 36.87 and 36.73 times to pure ZnIn2S4, respectively, owning to the enhanced charge accumulation and mass transfer according to in-situ spectroscopies and computational simulations of the built-in electrical field. Near-unity selectivity of benzaldehyde is achieved via the effective separation enabled by the Cu(II)-mediated conformation flipping of the intermediates and subsequent -pi conjugation. This work demonstrates an inspiring proof-of-concept nanoreactor design of photocatalysts for coupled sustainable systems.

H2O2 plays an irreplaceable role in many aspects of human society, such as paper bleaching, medical disinfection, wastewater treatment, organic synthesis, hydrometallurgy and the electronic industry. However, the unsustainability of the current industrial production process of traditional anthraquinone has a serious conflict with the green sustainable development. The photo/electrocatalytic H2O2 production from renewable energy has the advantages of being more economical, low-carbon and green, and in line with the requirements of energy economy. These catalytic methods of green H2O2 production have played a demonstrative role in the development of many small molecules, contributing to a fundamental understanding of general catalysis and providing a scientific perspective for future new energy cycles. In this review, the authors aim to integrate the reaction process and mechanism of photocatalytic and electrocatalytic H2O2 production, summarize the development and application of photocatalytic and electrocatalytic H2O2 production in recent years, and assess the modern technologies promoted in the process of H2O2 production research, including the development of flux production equipment and reaction coproduction, etc. This review intends to provide a clear logic profile and new directions for the development of H2O2 production, and calls for more researchers to provide more insights into the development of this field.

ZnO@ZnO2 shows ∼100% 2e− ORR selectivity in neutral media and a rate of 5.47 mol gcat−1 h−1 and an FE of 95.5% in bulk H2O2 production. The in situ growth of ZnO2 on ZnO restructures the operation active sites to facilitate a superior 2e− ORR activity.

The alloying of noble metals with Cu is one of the most effective strategies for improving catalytic performance and reducing cost in electrocatalytic carbon dioxide reduction reactions (CO2RR). Previous works usually focused on the influence of morphology and composition on the catalytic activity, but lacked the study of the valence state ratio of metals and the electron transfer behavior on alloys. In this work, PdCu−2 alloy (Pd/Cu molar ratio is 1:2) was obtained by a simple one-step solvothermal method, which can effectively convert CO2 to CO with a maximum Faradaic efficiency (FE) of 85% at −0.9 V (vs. RHE). Then, the effect of the chemical state of Pd and Cu on the catalytic performance was investigated. The X-ray photoelectron spectroscopy (XPS) shows that the binding energy of Pd in PdCu alloy has a negative shift, which has affected the adsorption of key intermediates. When the proportion of oxidized state and zero-valent metal in the alloy is about 1:2, the PdCu alloy shows the best catalytic activity. In addition, the transient photovoltage (TPV) measurements further demonstrate that due to the introduction of Cu, the electron transfer rate of PdCu−2 becomes the slowest, which helps the accumulation of electrons on PdCu−2 and leads to the improvement of catalytic performance for electrocatalytic CO2RR. This work can provide more insights into the alloy catalysts of electrocatalytic CO2RR.

Carbon dots (CDs) with good water solubility and biocompatibility have become a research hotspot in the nano-enzyme and biomedical field. However, the problems of low catalytic activity and ambiguous catalytic site of CDs as nanozymes still need to be addressed. In this work, CDs loaded with Cu single atoms are obtained through pyrolysis, and the coordination structure and surface functional groups are regulated by adjusting the pyrolysis temperature. CDs obtained at 300 °C (named Cu-CDs-300) have the most carboxyl content and Cu is coordinated in the form of CuN2 O2 , which can better decompose H2 O2 to produce free radical and is beneficial to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The vmax is 6.56*10-7  m s-1 , 6.56 times higher than that of horseradish peroxidase (HRP). Moreover, Cu-CDs-300 can effectively lead to CT26 apoptosis by generating much free radicals. This work demonstrates the synergistic effect of oxygen-containing functional groups and metal coordination structures on peroxide-like activity of CDs and provides new ideas for the design of clear active structure and high efficiency peroxide-like single atom CDs catalyst.

Porous flexible iridium nanosheets (Ir-PFNSs) with compressive strain were obtained by annealing 3R phase iridium oxide (3R-IrO 2 ) in a hydrogen atmosphere, which can exhibit excellent acid HER activity by a new three-hydrogen-involved mechanism.

Electrocatalytic two-electron (2e- ) oxygen reduction reaction (ORR) is a promising method to realize the sus-tainable production of H2O2. However, the 4e- pathway competes with 2e- ORR, presenting a challenge to the design of highly selective, low-cost catalysts. In addition to the design of active sites, the regulation on elec-trocatalytic kinetics is another strategy to get ideal 2e- ORR route. Here, cobalt doped carbon dots (CDs-Co) were used to regulate the electron transport kinetics on polyaniline (PANI) by constructing p-n heterojunction. The electron transfer kinetics and oxygen molecular activation process on PANI/CDs-Co were studied and analyzed using the transient photo-induced voltage (TPV) and pulse voltage-induced current (PVC) technologies, respectively. These results show that CDs-Co not only reduces the over-potential of oxygen molecular activation, but also reduces the transient electron concentration on PANI, which effectively improves the selectivity and activity of H2O2 production via ORR. The obtained PANI/CDs-Co-2 shows a H2O2 selectivity nearly 100.0% higher than that of PANI (76.3%). And it exhibits a H2O2 productivity of 3.5 mol g-cat1 h-1 at 0 V vs. RHE tested by gas diffusion electrode device. This work provides new insights for the design of 2e- ORR catalysts and the study of electrocatalytic kinetics.

Photoreduction is a sustainable method for the removal of the harmful heavy metal ions. However, the low photocatalytic activity due to limited solar energy utilization and sluggish separation of photogenerated electrons/hole pairs is a major challenge. Here, we report the design and preparation of SnS2/SnS heterojunction nanosheets with full-band response for efficient photoreduction of Cr(VI). The SnS2/SnS heterojunction has a three-dimensional lamellar structure with tight interfacial links that facilitate inter-electron hole transport. Among the samples, SnS2/SnS-2 (Sn4+: Sn2+ = 1: 0.218) shows optimal photoreduction of Cr(VI) under simulated solar light. Remarkably, SnS2/SnS-2 exhibited a high removal rate of Cr(VI) under all-weather conditions, with 50% removal achieved in 2 h under sunlight and 10% removal in 2 h under cloudy condition in neutral lake water, indicating practical catalytic performance and energy-saving potential. The presence of SnS not only improves the optical absorption capacity in the near-infrared region and enhances the photo-thermal conversion efficiency, but also accelerates the separation ability of photogenerated carriers, leading to high photocatalytic efficiency. Our work provides a promising concept for continuous Cr(VI) removal under all-weather conditions, including weak light irradiation.

The oxygen evolution reactions in acid play an important role in multiple energy storage devices. The practical promising Ru-Ir based catalysts need both the stable high oxidation state of the Ru centers and the high stability of these Ru species. Here, we report stable and oxidative charged Ru in two-dimensional ruthenium-iridium oxide enhances the activity. The Ru0.5Ir0.5O2 catalyst shows high activity in acid with a low overpotential of 151 mV at 10 mA cm(-2), a high turnover frequency of 6.84 s(-1) at 1.44 V versus reversible hydrogen electrode and good stability (618.3 h operation). Ru0.5Ir0.5O2 catalysts can form more Ru active sites with high oxidation states at lower applied voltages after Ir incorporation, which is confirmed by the pulse voltage induced current method. Also, The X-ray absorption spectroscopy data shows that the Ru-O-Ir local structure in two-dimensional Ru0.5Ir0.5O2 solid solution improved the stability of these Ru centers.

Electrocatalytic CO2 reduction reaction (ECO2RR) is a typical small molecule conversion reaction, which involves multiple-proton-electron coupling processes. As a typical competitive reaction, hydrogen evolution reaction (HER) competes with ECO2RR for protons, thus increasing the diversity of reaction paths. In this work, PdCu alloy is an effective electrocatalyst for ECO2RR. After the combination of carbon dots (CDs) with PdCu alloy, the highly efficient ECO2RR on the surfaces of PdCu alloy turns to HER for the first time. The strong adsorption of electrons and protons by CDs altered the reaction path on the PdCu for ECO2RR, as confirmed by a series of characterizations and transient photo-induced voltage tests, leading to the switch of ECO2RR to HER. This work verifies the important role of CDs in the regulation of electron transfer and proton, realizes the interference of the multi-proton and multi-electron catalytic processes on the well-defined active center (or one active center), and gives us a new insight to design the reaction paths.

Promoting the photocatalytic activity of narrow bandgap materials in the near-infrared region is an economical and efficient but challenge strategy to increase the utilization of sunlight. In this work, SnS2 nanosheet is modified with polyaniline (PANI/SnS2) and employed as photocatalyst for the reduction of hexavalent chromium to trivalent chromium. With the introduction of PANI, the absorbance of PANI/SnS2 increases about three times than that of SnS2 under 800 nm wavelength irradiation, and the adsorption rate of PANI/SnS2 increases about 50 times than that of SnS2. The transient photovoltage data show that the surface effective charge (ne) of 3 % PANI/SnS2, PANI, and SnS2 are 0.32, 0.06 and 0.07, respectively, indicating the highly efficient electron-hole separation and rapid electron transfer of PANI/SnS2 composites. In acidic solution, PANI/SnS2 (10 mg) can reduce 20 mg/L Cr(VI) (30 mL contaminated water) within 2 h of solar light irradiation. It is interesting to find that PANI/SnS2 also realizes excellent photocatalytic performance with the degradation efficiency of 35 % under near-infrared light irradiation, and the Cr(VI) reduction constant rate of PANI/SnS2 is about 3 times than that of SnS2 in this wavelength range. The synergistic effect of PANI and SnS2 enables the catalyst to be applied for efficient photocatalytic degradation. This design strategy can also be used for the design of catalysts for other catalytic systems.

Biomass-derived catalysts represent one of the greener alternatives for green catalysis. Oxygen reduction electrocatalysts with high efficiency, low cost and large-scale production are the key to promote the commercialization of new energy technology, such as, metal-air battery. Herein, the cheap and available spirulina was used as the carbon source, and a metal-free and porous carbon catalyst (C111-900) was prepared using dual template and solid reaction strategy. The porous structure also regulates the dynamic process of interface charge transfer, which keeps the fast process part of the charge transfer consistent while accelerating the slow process. As a result, C111-900 performs exceptionally well in alkaline media, achieving close to 20% Pt/C, including the half-wave potential, limiting current density and catalytic selectivity. Additionally, it exhibits higher power density (138.5 mW cm-2), specific capacity (766.4 mAh gZn- 1), energy density (958 Wh kgZn- 1) and has greater stability under high current discharge conditions than 20% Pt/C in Zn-Air batteries

Achieving multi-functions integrating reaction, separation and concentration into one-step catalysis process is a great challenge. Photocatalytic H2O2 generation is the cleanest and cheapest way for its production. Herein, an all-in-one photocatalytic device for H2O2 generation was designed by catalysis layer with ZIF-8/C3N4 composite and carbon dots-based evaporation layer (CDE). With this device, H2O2 solution with high concentration is obtained, and no need for extra separation and concentration processes. Under 2 sun illumination (3 h), H2O2 evolution reaches 17.13 mu mol and H2O2 solution concentration gets to 10.15 mmol L-1. Mole fraction of H2O2 solution obtained by all-in-one device is 1.86 times more concentrated than that of not concentrated H2O2 solution. Besides, multiples devices can work concurrently to realize large-scale production and gain large amounts of H2O2 solution with high concentration. Moreover, all-in-one devices can be reused at least ten cycles. The relation between the structure and performance of the photocatalysis device is further studied by COMSOL Multiphysics software and mathematical analysis. All-in-one photocatalytic device promotes H2O2 photoproduction closer to the practical application due to realizing continuous production of amounts of aqueous solution of H2O2 with high concentration in one-step.

Direct electrosynthesis of hydrogen peroxide (H2O2) via two‐electron pathway oxygen reduction reaction (2e− ORR) is crucially essential for a sustainable green economy. However, catalysts inevitably undergo four‐electron pathway oxygen reduction reaction (4e− ORR), resulting in low selectivity and economic benefits. The current challenge is to provide a feasible design strategy for obtaining satisfactory 2e− ORR catalysts with high selectivity. In this work, carbon dots (CDs) act as a cocatalyst to regulate the electron transport kinetics of In2O3/CDs, and the influence of CDs on the ORR pathways of In2O3/CDs is also studied. The electron transfer kinetics on In2O3/CDs composites are studied and analyzed using the transient photo‐induced voltage (TPV) technology. Combining the TPV results and kinetics analysis, it is shown that the electron transport on the In2O3 interface is obviously weakened after the addition of CDs, resulting in a high H2O2 selectivity. It is also demonstrated that CDs can effectively enhance the selectivity of H2O2, and the H2O2 selectivity of In2O3/CDs–10 is in close proximity to 100%, which is much higher than that of pure In2O3 (72%). This work will provide a new understanding and insight into addressing the challenge of low H2O2 selectivity for 2e− ORR catalysts.

Carbon dots (CDs), as a unique zero-dimensional member of carbon materials, have attracted numerous attentions for their potential applications in optoelectronic, biological, and energy related fields. Recently, CDs as catalysts for energy conversion reactions under multi-physical conditions such as light and/or electricity have grown into a research frontier due to their advantages of high visible light utilization, fast migration of charge carriers, efficient surface redox reactions and good electrical conductivity. In this review, we summarize the fabrication methods of CDs and corresponding CD nanocomposites, including the strategies of surface modification and heteroatom doping. The properties of CDs that concerned to the photo- and electro-catalysis are highlighted and detailed corresponding applications are listed. More importantly, as new non-contact detection technologies, transient photo-induced voltage/current have been developed to detect and study the charge transfer kinetics, which can sensitively reflect the complex electron separation and transfer behavior in photo-/electro-catalysts. The development and application of the techniques are reviewed. Finally, we discuss and outline the major challenges and opportunities for future CD-based catalysts, and the needs and expectations for the development of novel characterization technologies.

The regulation of interface electron-transfer and catalytic kinetics is very important to design the efficient electrocatalyst for alkaline hydrogen oxidation reaction (HOR). Here, we show the Pt-Ni alloy nanoparticles (PtNi2) have an enhanced HOR activity compared with single component Pt catalyst. While, the interface electron-transfer kinetics of PtNi2 catalyst exhibits a very wide electron-transfer speed distribution. When combined with carbon dots (CDs), the interface charge transfer of PtNi2-CDs composite is optimized, and then the PtNi2-5 mg CDs exhibits about 2.67 times and 4.04 times higher mass and specific activity in 0.1 M KOH than that of 20% commercial Pt/C. In this system, CDs also contribute to trapping H+ and H2O generated during HOR, tuning hydrogen binding energy (HBE), and regulating interface electron transfer. This work provides a deep understanding of the interface catalytic kinetics of Pt-based alloys towards highly efficient HOR catalysts design.