Improved charge injection of edge aligned MoS2/MoO2 hybrid nanosheets for highly robust and efficient electrocatalysis of H2 production

Synthesis of a carbon-wrapped microsphere MoO2/Mo2C heterojunction as an efficient electrocatalyst for the oxygen reduction reaction and the hydrogen evolution reaction

The development of non-noble metal catalysts for the optimization of conversion and storage devices is an important research topic. Hence, the microsphere MoO2/Mo2C/C heterojunction composites, which play an important role in the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER), were synthesized using the solvothermal-sintering method. The results revealed that the as-prepared composite exhibited better ORR and HER catalytic performances than those of MoO2/Mo2C and Vulcan XC-72R (carbon black), and approaching that of commercial Pt/C. At the same time, it has a superior methanol tolerance and electrochemical stability than that of the commercial Pt/C. The excellent performance may be attributed to the synergistic effect of the MoO2/Mo2C heterostructure, highly conductive Vulcan XC-72R, and oxygen vacancies (Ov). This research offers new insights into the design and synthesis of cost-effective, environmentally friendly heterojunction composite catalysts used as a high-performance cathode material in fuel cells and water splitting.

Surface Engineering of Cr-Doped Cobalt Molybdate toward High-Performance Hydrogen Evolution

Replacing commercial noble metal catalysts with earth-abundant metal catalysts for hydrogen production is an important research direction for electrolytic water. Improving the catalytic performance of non-noble metals while maintaining stability is a key challenge for alkaline hydrogen evolution. Herein, we combined alkali etching and surface phosphating to regulate the properties of Cr-doped CoMoO₄ material, forming a surface structure in which amorphous cobalt phosphate and Cr-doped Co(Mo)O_x coexist. As expected, the as-prepared catalytic material exhibits remarkable hydrogen evolution activity in 1.0 M KOH, only requiring a low overpotential of 52.7 mV to achieve a current density of 10 mA cm^-2, and can maintain this current density for 24 h. The characterization and analysis of the catalyst before and after the stability test reveal that the Cr doping and surface engineering (i.e., alkali etching and phosphating) synergistically increase the adsorption and dissociation of water, optimize the desorption of H, and ultimately accelerate hydrogen evolution. This work provides a new strategy for tailoring nonprecious metal materials to improve the hydrogen production from water electrolysis.

Two-Dimensional MoO2 Nanosheet Composite Hydrogels with High Transmittance and Excellent Photothermal Property for Near-Infrared Responsive Actuators and Microvalves

Stimulus-responsive intelligent hydrogel actuators have highly promising applications in the fields of soft robotics, smart manipulators, and flexible devices. Near-infrared (NIR) light is considered an ideal method to trigger the response behavior remotely and precisely. In order to realize the excellent optical transmittance and photothermal property of NIR-responsive hydrogels at the same time, two-dimensional nonlayered MoO₂ nanosheets (2D-MoO₂) with excellent photothermal efficiency (62% under an NIR light irradiation of 808 nm), splendid chemistry stability, and low preparation cost are used as photothermal agents and incorporated into the poly(N-isopropylacrylamide) (PNIPAM) hydrogel network, forming the 2D-MoO₂/Laponite/PNIPAM ternary nanocomposite hydrogel (TN hydrogel). It is remarkable that compared with the GO and MXene hydrogels with the same agent content (1.0 mg mL^-1) and thickness (1 mm) whose transmittance values are only ∼5% at 600 nm, the TN hydrogel shows a similar NIR-responsive temperature, but much higher optical transmittance (∼53%). Besides, of the three hydrogels with similar transmittance, the TN hydrogel shows a much higher NIR-responsive temperature. The TN hydrogel with a low loading of 2D-MoO₂ (1.5 mg mL^-1) can produce a significant temperature increase of ∼30 °C after the application of 0.8 W cm^-2 NIR light irradiation for 15 s. Impressively, the TN hydrogel exhibits excellent anti-fatigue property, keeping a fast response and temperature rise behavior even after 50 times of heating-cooling cycles. The flexibly controllable and reversible deformation is realized by a well-designed bilayer structure even in harsh environments. The transparent and asymmetric bilayer hydrogel is further used as a soft manipulator to capture objects visually and accurately. The NIR light-controlled microvalve based on this composite hydrogel is also demonstrated. This work provides a novel kind of transparent hybrid NIR response hydrogel for the further development of smart, programmable, reversible hydrogel-based actuators and soft robotics.

Construction of MoO2@MoS2 heterostructures in situ on carbon cloth for the hydrogen evolution reaction

MoO2@MoS2 heterostructures in situ grown on carbon cloth were developed for efficient hydrogen evolution reaction.

In situ modulation of silica-supported MoO2/Mo2C heterojunction for enhanced hydrogen evolution reaction

Hydrogen being a promising source of clean energy, the production of hydrogen using electrocatalysis and the development of carbon-neutral energy conversion technologies are crucial.