Shuo Chen

Seawater is widely abundant on Earth and is considered an “unlimited” resource for hydrogen production via water electrolysis. However, seawater electrolysis is challenging due to impurity-induced side reactions. A selective and durable electrocatalyst is highly desired, especially for the sluggish oxygen evolution reaction (OER). In this talk, I will present our recent efforts to develop such OER electrocatalysts. Specifically, we investigated FeMoₓOᵧ-derived materials. We quantified the Mo leaching process in the precursor and identified the active species after surface reconstruction. An overpotential of 313 mV was required to achieve 1.0 A cm⁻² in both simulated alkaline seawater (1 M KOH + 0.5 M NaCl) and high-chloride conditions (1 M KOH + 1.5 M NaCl). Notably, in actual alkaline seawater (1 M KOH + seawater), our electrocatalyst required only 321 mV to deliver the same current density and remained stable for 400 h. In addition, I will introduce promising approaches to scale up our electrocatalysts for high-current (A cm⁻²) seawater oxidation.

Aqueous Zn//V₂O₅ batteries (ZVBs) hold promise for large-scale energy storage due to their high safety and low cost, but face critical challenges of Zn dendrite growth and parasitic side reactions at the Zn anode, coupled with severe vanadium dissolution and shuttle at the V₂O₅ cathode. Conventional strategies, such as electrolyte engineering or separator modifications, often focus on single-component optimization, neglecting synergistic anode and cathode regulation. Herein, we developed a Zeolite Socony Mobil-5 (ZSM-5) filled glass fiber separator (ZSM-5@GF) to address these issues simultaneously. The ZSM-5 zeolite facilitates the Zn²⁺ desolvation via binding H₂O molecules, suppressing HER and side reactions. And it could also homogenize the ion concentration distribution for dendrite-free Zn plating/stripping. Concurrently, ZSM-5 zeolite could also immobilize dissolved vanadium species via electrostatic adsorption, mitigating cathode degradation and shuttle-induced capacity fading. Benefiting from the synergistic anode/cathode interface regulation, both electrodes dramatically extended their cycle life, and an Ah-level pouch-type Zn//V₂O₅ cell is also realized for continuous cycling. This bifunctional separator realizes synergistic stabilization of the Zn anode and V₂O₅ cathode, offering a cost-effective and scalable strategy for high-performance AZVBs toward practical applications.

The development of efficient and stable oxygen evolution reaction (OER) electrocatalysts for seawater electrolysis is vital to enable sustainable hydrogen production in coastal and arid regions without further burdening scarce freshwater resources. Here, we report the design of an iron-modified cobalt–chromium layered double hydroxide (Fe–CoCr LDH) derived from a cobalt-based metal–organic framework (Co MOF) for the OER in alkaline seawater media. The synthesis was carried out entirely at room temperature using a rapid, solution-based process. The resulting Fe–CoCr LDH catalyst demonstrates high OER activity, achieving low overpotentials of 250, 300, and 320 mV at current densities of 100, 500, and 1000 mA cm⁻², respectively. Furthermore, the catalyst exhibits very good long-term stability in both 1 M KOH and 6 M KOH natural seawater, maintaining performance over 100 hours at 100 and 500 mA cm⁻². These results highlight the potential of earth-abundant transition metal-based LDHs as efficient OER electrocatalysts for seawater electrolysis applications.

Magnetism in two-dimensional (2D) van der Waals (vdW) crystals offers promising new directions for low-dimensional physics and devices. In this work, mega-electron volt (MeV) ultrafast electron diffraction was employed to investigate the ultrafast atomic dynamics of a novel, 2D vdW magnetic single-crystal CrSBr. Femtosecond (fs) optical pump pulses excited non-equilibrium atomic displacements shown to be coherent acoustic phonons (CAPs). Phonon frequencies were extracted by analyzing oscillations of different Bragg peak (BP) intensities and were determined to be GHz acoustic disturbances that propagated as strain waves. Phonon modes exhibit anisotropy with respect to the a and b crystal axes. Subharmonic phonon frequencies were also observed, and this provided a signature of nonlinear oscillatory coupling between the laser-induced pumping phonon frequency and secondary phonon frequencies. Thus, CrSBr was found to serve as a nonlinear phononic frequency converter. The ultrafast time dependence of the Bragg intensity was simulated by incorporating an oscillating deviation parameter ansatz into expressions for the dynamical scattering intensity yielded excellent modeling of the ultrafast structural dynamics of the photo-excited 2D crystal. Our work provides a foundation for exploring how fs light pulses can influence phonon dynamics in materials with strong spin-lattice coupling. These results suggest that CAPs can match the magnon frequencies and show the promise of CrSBr for use in optical-to-microwave transducers and phononic devices.

Studies of vacancy-mediated anomalous transport properties have flourished in diverse fields since these properties endow solid materials with fascinating photoelectric, ferroelectric, and spin-electric behaviors. Although phononic and electronic transport underpin the physical origin of thermoelectrics, vacancy has only played a stereotyped role as a scattering center. Here we reveal the multifunctionality of vacancy in tailoring the transport properties of an emerging thermoelectric material, defective n-type ZrNiBi. The phonon kinetic process is mediated in both propagating velocity and relaxation time: vacancy-induced local soft bonds lower the phonon velocity while acoustic-optical phonon coupling, anisotropic vibrations, and point-defect scattering induced by vacancy shorten the relaxation time. Consequently, defective ZrNiBi exhibits the lowest lattice thermal conductivity among the half-Heusler family. In addition, a vacancy-induced flat band features prominently in its electronic band structure, which is not only desirable for electron-sufficient thermoelectric materials but also interesting for driving other novel physical phenomena. Finally, better thermoelectric performance is established in a ZrNiBi-based compound. Our findings not only demonstrate a promising thermoelectric material but also promote the fascinating vacancy-mediated anomalous transport properties for multidisciplinary explorations.

NiMo-based nanostructures are among the most active hydrogen evolution reaction (HER) catalysts under an alkaline environment due to their strong water dissociation ability. However, these nanostructures are vulnerable to the destructive effects of H₂ production, especially at industry-standard current densities. Therefore, developing a strategy to improve their mechanical strength while maintaining or even further increasing the activity of these nanocatalysts is of great interest to both the research and industrial communities. Here, a hierarchical interconnected NiMoN (HW-NiMoN-2h) with a nanorod-nanowire morphology was synthesized based on a rational combination of hydrothermal and water bath processes. HW-NiMoN-2h is found to exhibit excellent HER activity due to the accomodation of abundant active sites on its hierarchical morphology, in which nanowires connect free-standing nanorods, concurrently strengthening its structural stability to withstand H₂ production at 1 A cm⁻². Seawater is an attractive feedstock for water electrolysis since H₂ generation and water desalination can be addressed simultaneously in a single process. The HER performance of HW-NiMoN-2h in alkaline seawater suggests that the presence of Na⁺ ions interferes with the reation kinetics, thus lowering its activity slightly. However, benefiting from its hierarchical and interconnected characteristics, HW-NiMoN-2h is found to deliver outstanding HER activity of 1 A cm⁻² at 130 mV overpotential and to exhibit excellent stability at 1 A cm⁻² over 70 h in 1 M KOH seawater.