Nanoparticles Embedded in MOFs with Surface Conductance Enhancement for Efficient Electrocatalytic Water Splitting

A novel nanoporous NiAl-LDH nanosheet array with optimized Ni active sites is prepared for efficient electrocatalytic alkaline water splitting.

Developing a hydrogen economy to replace traditional fossil fuels is essential for sustainable human development. As two promising H2 production strategies, photocatalytic and electrocatalytic water splitting with large reaction energy barriers still face the great challenges of poor solar-to-hydrogen efficiency and large electrochemical overpotentials, respectively. Herein, a new strategy is proposed to disassemble the difficult pure water splitting into two parts that are easy to implement, namely mixed halide perovskite photocatalytic HI splitting for H2 production, and simultaneous electrocatalytic I3 - reduction and O2 production. The efficient charge separation, abundant H2 production active sites, and a small HI splitting energy barrier contribute to the superior photocatalytic H2 production activity of MoSe2 /MAPbBr3- x Ix (CH3 NH3 + = MA). Subsequent electrocatalytic I3 - reduction and O2 production reactions only need a small voltage of 0.92V to drive, which is far lower than that of the electrocatalytic pure water splitting (>1.23V). The molar ratio of H2 (6.99mmol g-1 ) to O2 (3.09mmol g-1 ) produced during the first photocatalytic and electrocatalytic cycle is close to 2:1, and the continuous circulation of I3 - /I- between the photocatalytic and electrocatalytic systems can achieve efficient and robust pure water splitting.

The development of porous metal phosphides with abundant active sites is of great importance for efficient electrocatalytic water splitting.

Developing inexpensive transition-metal-based nanomaterials with high electrocatalytic activity is of significant necessity for electrochemical water splitting. In this study, we propose a controllable structural engineering strategy of constructing a hyperbranched architecture for highly efficient hydrogen evolution reaction/oxygen evolution reaction (HER/OER). Hyperbranched NiCoP architecture organized by hierarchical nanorod-on-nanosheet arrays is rationally prepared as a demonstration via a facile solvothermal and phosphorization approach. A strong synergistic benefit from the multiscale building blocks is achieved to enable outstanding electrocatalytic properties in an alkaline electrolyzer, including low HER and OER overpotentials of 71 and 268 mV at 10 mA cm-2, respectively, which significantly outperforms the counterparts of individual nanorods and nanosheets. The bifunctional catalysts also show highly efficient and durable overall water electrocatalysis with a small voltage of 1.57 V to drive a current density of 10 mA cm-2. The present study will open a new window to engineering hyperbranched architectures with exceptional electrocatalytic activities toward overall water splitting.

Efficient electrocatalytic overall water splitting and structural evolution of cobalt iron selenide by one-step electrodeposition

Although a great achievement has been made in the field of electrochemistry, the exploration of high-efficiency catalysts for the generation of hydrogen and oxygen via overall water splitting is still a grand challenge. We herein report the successful construction of a new class of hierarchical catalysts with defect-enriched nickel-molybdenum phosphide nanosheets anchored on the surface of carbon nanotubes for efficient water splitting. Via the construction of a hierarchical nanostructure, more efficient electron mobility and mass transfer occurrence were achieved, resulting in a substantial enhancement of electrocatalytic performances. Interestingly, overpotentials of only 255 and 135 mV are required for the optimized Ni1Mo1P NSs@MCNTs to afford a current of 10 mA cm-2 for oxygen evolution reaction and hydrogen evolution reaction, respectively. More significantly, the introduction of molybdenum and phosphorus is also significant for exposing surface active sites and modifying the bonding energy between hydrogen and metals; all of these advantages have endowed the Ni1Mo1P NSs@MCNTs//Ni1Mo1P NSs@MCNTs couple to display highly efficient water electrocatalysis property with a relatively low overall potential of 1.601 V at 10 mA cm-2, shedding bright light for large-scale overall water electrocatalysis.

Metallic Mo2C anchored pyrrolic-N induced N-CNTs/NiS2 for efficient overall water electrolysis

An integration hydrogen adsorption benign component such as a metal with an oxygen-containing reactant adsorption benign component such as metal oxide allows for efficient overall water splitting in alkaline solutions and yet remains a considerable challenge. Herein, 5d transition metal oxide WO2 and WO3 (denoted as WOx) nanoparticles are purposely integrated with a porous Ni nanosheet array grown on nickel foam (NF) to design a strongly coupled Ni/WOx/NF porous nanosheet array electrocatalyst. Through the anion exchange of Ni(OH)2 nanosheets with tungstate, followed by hydrogenation treatment, abundant Ni/WOx interfaces with strong coupling interaction are generated. Benefiting from the strong synergies between Ni and WOx and the unique nanostructure, Ni/WOx/NF only requires the overpotentials of 42 mV for hydrogen evolution reaction (HER) and 395.7 mV for oxygen evolution reaction (OER) to achieve the current densities of 10 and 100 mA cm-2, respectively. Furthermore, the Ni/WOx/NF can achieve a current density of 10 mA cm-2 at a low cell voltage of 1.54 V in a two-electrode system. This work opens a novel avenue for the design of high-performance but low-cost electrocatalysts for overall water splitting.

Emerging single-atom catalysts for efficient electrocatalytic CO2 reduction and water splitting: Recent advances

The d-p hybridized Nb─O3 sites in NaNbO3 generate unoccupied states near the Fermi level, inducing negative self-adsorption and thermodynamic barriers in electrocatalytic water splitting. In this work, an innovative strategy is introduced by incorporating tellurium atoms into NaNbO3, wherein the engineered p-p orbital coupling dynamically competes with the intrinsic d-p hybridization, thereby effectively modulating bulk charge delocalization. Remarkably, the p-p orbital coupling populates unoccupied states near the Fermi level, thereby optimizing the reaction pathway for the oxygen evolution reaction (OER) and synergistically enhancing the overall water splitting efficiency. Additionally, the incorporation of Te─O3 sites modulates the intrinsic reactivity of NaNbO3 and serves as supplementary catalytic active centers. The optimized electrocatalyst exhibits outstanding catalytic activity, achieving low overpotentials of 68.00mV for the hydrogen evolution reaction (HER) and 283.40mV for the OER at a current density of 10mA cm-2, coupled with an efficient overall water splitting cell voltage of 1.65V. Overall, the p-p orbital competition strategy effectively addresses the longstanding activity-stability trade-off in NaNbO3 electrocatalysts by reconfiguring electron delocalization pathways, enhancing both active site accessibility and structural integrity, thereby bridging a critical performance gap in perovskite-based electrocatalysts for efficient overall water splitting.

NiFeP nanosheets on N-doped carbon sponge as a hierarchically structured bifunctional electrocatalyst for efficient overall water splitting

Single atomic Ru in TiO2 boost efficient electrocatalytic water oxidation to hydrogen peroxide

Design and synthesis of Cu modified cobalt oxides with hollow polyhedral nanocages as efficient electrocatalytic and photocatalytic water oxidation catalysts

Electrocatalytic water splitting is a crucial area in sustainable energy development, and the development of highly efficient bifunctional catalysts that exhibit activity toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance. Co3O4 is a promising candidate catalyst, owing to the variable valence of Co, which can be exploited to enhance the bifunctional catalytic activity of HER and OER through rational adjustments of the electronic structure of Co atoms. In this study, we employed a plasma-etching strategy in combination with an in situ filling of heteroatoms to etch the surface of Co3O4, creating abundant oxygen vacancies, while simultaneously filling them with nitrogen and sulfur heteroatoms. The resulting N/S-VO-Co3O4 exhibited favorable bifunctional activity for alkaline electrocatalytic water splitting, with significantly enhanced HER and OER catalytic activity compared to pristine Co3O4. In an alkaline overall water-splitting simulated electrolytic cell, N/S-VO-Co3O4 || N/S-VO-Co3O4 showed excellent overall water splitting catalytic activity, comparable to noble metal benchmark catalysts Pt/C || IrO2, and demonstrated superior long-term catalytic stability. Additionally, the combination of in situ Raman spectroscopy with other ex situ characterizations provided further insight into the reasons behind the enhanced catalyst performance achieved through the in situ incorporation of N and S heteroatoms. This study presents a facile strategy for fabricating highly efficient cobalt-based spinel electrocatalysts incorporated with double heteroatoms for alkaline electrocatalytic monolithic water splitting.

Hydrogen production by electrocatalytic water splitting is considered to be an effective and environmental method, and the design of an electrocatalyst with high efficiency, low cost, and multifunction is of great importance. Herein, we developed a amorphous Co-FeOOH/crystalline CoCe-MOF heterostructure (defined as Co-FeOOH/CoCe-MOF/NF) though a convenient cathodic electrodeposition strategy as a high-efficiency bifunctional electrocatalyst for water electrolysis. The Co-FeOOH/CoCe-MOF/NF nanocrystals provide remarkable electronic conductivity and plenty of active sites, and the crystalline/amorphous heterostructure with generates synergistic effects, providing plentiful active sites and efficient charge/mass transfer. Benefiting from this, the designed Co-FeOOH/CoCe-MOF/NF displays ultralow overpotentials of 226 and 74 mV to achieve 10 mA cm-2 for oxygen evolution reaction and hydrogen evolution reaction, and also shows the superior performance for overall water splitting with a low voltage of 1.55 V at 10 mA cm-2 in 1 M KOH. The work reveals a design of superior activity, cost-effective and multifunctional electrocatalysts for water splitting.