Hui Liu

Electrochemical water electrolysis for hydrogen production offers a feasible way for renewable energy development but still faces significant challenges. Developing high-performance catalysts with high activity, low cost, long-term stability, corrosion resistance, and antisediment aggregation is crucial for the practical application of water electrolysis, particularly seawater electrolysis. For this purpose, we designed a Ni(Fe)P/Ni(Fe)OOH/MXene composite electrocatalyst on an iron foam substrate, which uses a multi-interface structure, Fe self-doping, and incomplete phosphating to jointly adjust the electronic structure and optimize H* absorption. Importantly, the incorporation of MXene significantly enhances electrical conductivity, increases the exposure sites, and facilitates gas release, thereby boosting the hydrogen evolution reaction (HER) performance. Meanwhile, the self-doping of the substrate and vertically staggered nanosheet morphology induced by MXene are utilized to enhance the bonding between the catalyst and substrate, as well as the antisediment aggregation performance, thereby achieving long-term stable operation in an alkaline seawater environment. Consequently, the catalyst demonstrates outstanding HER behavior, achieving 100 mA cm–2 at 140 mV in freshwater and 165 mV in seawater, while maintaining stability for 45 h. Moreover, Ni(Fe)P/Ni(Fe)OOH/MXene was assembled with Fe-Ni(OH)2 into a dual-electrode electrolysis cell, achieving 10 mA cm–2 at only 1.49 V in freshwater, and 1.56 V in natural seawater. This work may open up a prospect for freshwater electrolysis of high efficiency HER catalyst.

The electrochemical co-reduction of carbon dioxide (CO₂) and nitrate (NO₃ ⁻) to urea presents a sustainable strategy to alleviate the ecological and food crisis. However, the current urea electrosynthesis faces low selectivity issues due to the high energy barrier of C–N coupling, as well as the unbalanced supply of key intermediates. Herein, we report that a Au-doped Cu bimetallic catalyst effectively balances the supply of C-containing and N-containing intermediates, thereby enhancing urea selectivity. In situ Raman spectroscopy and density functional theory calculations demonstrate that doping Au into Cu enhances the surface coverage of the *CO intermediate and optimizes the adsorption energy of *NO, thereby lowering the energy barrier of C–N coupling from 0.44 eV on the Cu surface to 0.15 eV on the Cu–Au surface. Meanwhile, this doping engineering also suppresses the reactions competing with urea electrosynthesis. As a result, the Cu–Au catalyst achieves a urea faradaic efficiency of 67.81% and a yield rate of 49.34 μmol cm⁻² h⁻¹ at −0.4 V versus the reversible hydrogen electrode.

In this work, the Cu single-atom catalysts (SACs) supported by metal-oxides (Al₂O₃-Cu_SAC, CeO₂-Cu_SAC, and TiO₂-Cu_SAC) are used as theoretical models to explore the correlations between electronic structures and CO₂RR performances. For these catalysts, the electronic metal-support interaction (EMSI) induced by charge transfer between Cu sites and supports subtly modulates the Cu electronic structure to form different highest occupied-orbital. The highest occupied 3d_yz orbital of Al₂O₃-Cu_SAC enhances the adsorption strength of CO and weakens C-O bonds through 3d_yz-π* electron back-donation. This reduces the energy barrier for C-C coupling, thereby promoting multicarbon formation on Al₂O₃-Cu_SAC. The highest occupied 3d_z2 orbital of TiO₂-Cu_SAC accelerates the H₂O activation, and lowers the reaction energy for forming CH₄. This over activated H₂O, in turn, intensifies competing hydrogen evolution reaction (HER), which hinders the high-selectivity production of CH₄ on TiO₂-Cu_SAC. CeO₂-Cu_SAC with highest occupied 3d_x2-y2 orbital promotes CO₂ activation and its localized electronic state inhibits C-C coupling. The moderate water activity of CeO₂-Cu_SAC facilitates *CO deep hydrogenation without excessively activating HER. Hence, CeO₂-Cu_SAC exhibits the highest CH₄ Faradaic efficiency of 70.3% at 400 mA cm⁻².

Low interface oxide concentration is desired for III‐V semiconductor/high k dielectrics stacks to get high‐performance devices. The remote scavenging effect is observed upon Ti metal deposition on the InP/Al₂O₃ system, characterized by in situ angle resolved X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry, as well as ex situ cross‐sectional transmission electron microscopy. The mechanism is investigated by O¹⁸ tracing. Two mechanisms are proposed for this remote scavenging effect. The impact of this remote scavenging effect is studied by metal oxide semiconductor (MOS) capacitors fabrication and characterization. This work sheds light on InP‐based MOS devices.

Thin‐film ferroelectric of HfO₂‐based has gained broad interest for non‐volatile memories. The traditional theory with respect to doped hafnium oxide is based on the polycrystalline structure of the Pcb2₁ non‐centrosymmetric orthorhombic phase. While amorphous oxides also show ferroelectricity, which cannot be explained by the traditional theory. Here, ferroelectric‐like behavior is observed in the amorphous oxide‐based TaN/high‐k/Si system. Through strategically modulating the atomic layer of deposition conditions of the high‐k oxides, the evolution from paraelectric to ferroelectric‐like behavior is seen in TaN/Al₂O₃/Si capacitors. The interface chemistry of these stacks is systematically studied via in situ angle‐resolved X‐ray photoelectron spectroscopy. A mechanism for the ferroelectric‐like behavior is proposed based on interface ions‐vacancies displacement. This work sheds light on physics in ferroelectric‐like thin film devices.

The existing photoelectrodes for photoelectrochemical (PEC) cells are almost based on oxide semiconductors. Compared with n-type oxide photoanodes, p-type oxide photocathodes are rather rare and most are not suitable for unassisted water reduction because of their inappropriate band edge positions. Thus, it is highly desirable to exploit more kinds of p-type semiconductors for Z-scheme PEC cells. Commonly, organic semiconductors are p-type with a more negative band edge, which will give more options for photocathodes and provide new paths for sustainable overall water splitting. Herein, we report a PEC cell in which TiO₂ and the poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester bulk heterojunction (P3HT:PCBM BHJ) are connected by copper wires to achieve solar-driven overall water splitting in the absence of an external bias. The photocurrent density of the TiO₂–P3HT:PCBM system is about 145 μA cm⁻² and remains constant in a 9 h test duration under continuous illumination. The average H₂ and O₂ evolution rates of this system are about 2.38 μmol h⁻¹ and 1.16 μmol h⁻¹, respectively. The charge-to-chemical faradaic efficiency is 88.7%. These results confirm that a PEC cell for overall water splitting can be achieved by coupling the most representative inorganic semiconductor TiO₂ and the most considered organic material P3HT:PCBM.