• Energy Research

The interfacial structure in "giant" PbS/CdS quantum dots (QDs) was engineered by modulating the Cd:S molar ratio during in situ growth. The control of the gradient interfacial layer could facilitate hole transfer, regulate the transition from double- to single-color emission, as a consequence. These QDs are optically active close-to-the near-infrared (NIR) spectral region and are candidates as absorber materials in solar energy conversion. Photoinduced charge transfer from "giant" QDs to electron scavenger can still take place despite the ultra-thick (~5 nm) shell. The hybrid architecture based on a TiO2 mesoporous framework sensitized by the "giant" QDs with alloyed interface can produce a saturated photocurrent density as high as ~5.3 mA/cm2 in a photoelectrochemical (PEC) cell under 1 Sun illumination, which is around 2 times higher than that of bare PbS and core/thin-shell PbS/CdS QDs sensitizer. The as-prepared PEC device presented very good stability thanks to the "giant" core/shell QDs architecture with tailored interfacial layer and a further coating of the ZnS shell. 78% of the initial current density is kept after 2-h irradiation at 1 Sun. Engineering of electronic band structure plays a key role in boosting the functional properties of these composite systems, which hold great potential for H2 production in PEC devices.

Abstract Electrochemical CO2 reduction reaction (ECO2RR) offers an opportunity to sustainably convert CO2 into value-added fuels and chemicals by using the electricity that could be generated by renewable energies. Recently, enormous efforts are focused on the development of metal-based catalysts for the selective ECO2RR with high efficiency. Multi-metallic catalyst design emerges as one of the most promising strategies for the promotion of the Faradaic efficiency (FE), the current density, and the lowering of the overpotential of the catalysts for ECO2RR. The synergistic effects of the different metal sites in the hybrid catalysts are of significance for the enhancement of the ECO2RR performance. This review summarizes the rational design of multi-metallic catalysts, including alloy, atomically dispersed multi-metallic sites, and others, along with the popular metal elements studied in multi-metallic catalysts to clarify the advantages of different metal elements for ECO2RR. The density functional theory (DFT) simulations and advanced in-situ characterizations that contribute to demystifying the synergies between metal elements are highlighted. Challenges and outlook concerning the catalyst design and reaction mechanism of multi-metallic catalysts for ECO2RR are also discussed.

Based on the innovative strategy of EOR replacing OER, we originally proposed a “zinc–ethanol–air battery” achieving superior performance, which brought a new research direction for metal–air batteries.

AbstractOxygen reduction/evolution reactions (ORR/OERs) catalysts play a key role in the metal‐air battery and water‐splitting process. Herein, we developed a facile template‐free method to fabricate a new type of non–noble metal‐based hybrid catalyst which consists of binary FeNi alloy/nitride nanocrystals with graphitic‐shell and biomass‐derived N‐doped carbon (NC) (FexNiyN@C/NC). This novel nanostructure exhibits superior performance for ORR/OER, which can be attributed to the strong interactions between the graphitic‐shell encapsulated FeNi alloy/nitride nanocrystals and the N‐doped porous carbon substrate. The X‐ray absorption spectroscopy technique was employed to reveal the underlying mechanisms for the excellent performance. The assembled Zn‐air battery device exhibits outstanding charging/discharging performance and cycling stability, indicating the great potential of this type of novel catalysts.

Abstract Developing noble-metal-free electrocatalysts for hydrogen evolution reaction (HER) is highly desirable to realize the hydrogen energy economy. Nanostructures and carbon-based hybrids are introduced to increase active-site abundance and to promote mass transportation. Herein, we reported a facile strategy for the in situ synthesis of bimetallic alloy-metal carbide heterostructures on ultra-fine chitin derived N-doped carbon nanofibers (NCNFs). The chitin nanofibers have abundant functional groups including hydroxyl (–OH) and amino (–NH2), which can strongly catch the metal ions. After the carbonization process, the Mo0.84Ni0.16-Mo2C nanoparticles were in situ formed throughout the whole NCNFs. Owing to the unique 3D nanofibers network structure, large specific surface area and synergistic effects between the Mo0.84Ni0.16 alloy and Mo2C, the Mo0.84Ni0.16-Mo2C/NCNFs electrocatalysts exhibit excellent HER activity with low overpotentials of 183 mV (10 mA cm−2) and Tafel slope of 71 mV dec−1 in alkaline solution. Heterointerface engineering can optimize the chemical configurations of active sites toward intrinsically boosted HER kinetics. The Mo0.84Ni0.16-Mo2C/NCNFs display temperature-dependent HER activity and the 750 °C is the best carbonization temperature. In addition, the electrocatalysts exhibit outstanding stability during continuous HER electrolysis. This work provides a simple strategy to fabricate bimetal alloy metal carbide heterostructures.

AbstractLayered vanadates are ideal energy storage materials due to their multielectron redox reactions and excellent cation storage capacity. However, their practical application still faces challenges, such as slow reaction kinetics and poor structural stability. In this study, we synthesized [Me2NH2]V3O7 (MNVO), a layered vanadate with expended layer spacing and enhanced pH resistance, using a one‐step simple hydrothermal gram‐scale method. Experimental analyses and density functional theory (DFT) calculations revealed supportive ionic and hydrogen bonding interactions between the thin‐layered [Me2NH2]+ cation and [V3O7]− anion layers, clarifying the energy storage mechanism of the H+/Zn2+ co‐insertion. The synergistic effect of these bonds and oxygen vacancies increased the electronic conductivity and significantly reduced the diffusion energy barrier of the insertion ions, thereby improving the rate capability of the material. In an acidic electrolyte, aqueous zinc‐ion batteries employing MNVO as the cathode exhibited a high specific capacity of 433 mAh g−1 at 0.1 A g−1. The prepared electrodes exhibited a maximum specific capacity of 237 mAh g−1 at 5 A g−1 and maintained a capacity retention of 83.5% after 10,000 cycles. This work introduces a novel approach for advancing layered cathodes, paving the way for their practical application in energy storage devices.

Abstract Mixed-reactant microfluidic membraneless fuel cells are promising power sources for future electronic portable applications due to their simplified construction and operation. In order to develop a better performing mixed-reactant fuel cell, the improvement of elements such as selective catalysts and optimization of electrode-microchannel arrangements for cell stacking is of key importance. While we have previously worked on the catalysts approach, the next step is naturally to develop a microfluidic device for low power applications. Thus, this work focuses on developing a passive mixed-reactant fuel cell stack through numerical simulation studies, which allow better understanding of the phenomena occurring in the device and optimizing cell parameters based on simulation results. Two electrode arrangements were studied and the model pointed out the option with better fuel utilization and better oxygen supply, hence, stronger performance. The design was further improved by reducing the resistance between the electrodes, as indicated by the simulation. The resulting device was then fabricated and tested, reaching a maximum power density of 28 mW cm−2 with 4 M MeOH and it exhibited stable operation during at least 6 h. Based on this results, 4 mixed-reactant cells were incorporated in a single microfluidic device. The stack was tested in passive conditions producing 1.0 mW of peak power in series connection and it exhibited a stable operation. Moreover, the proof of concept was demonstrated by using the stack for powering a green LED during 4 h with a single charge of 234 μL.