Engineering vanadium phosphide by iron doping as bifunctional electrocatalyst for overall water splitting

Pt Single Atom-Doped Triphasic VP-Ni3P-MoP Heterostructure: Unveiling a Breakthrough Electrocatalyst for Efficient Water Splitting

Enhancement of an alkaline water splitting reaction in Pt-based single-atom catalysts (SACs) relies on effective metal-support interactions. A Pt single atom (PtSA)-immobilized three-phased PtSA@VP-Ni3P-MoP heterostructure on nickel foam is presented, demonstrating high catalytic performance. The existence of PtSA on triphasic metal phosphides gives an outstanding performance toward overall water splitting. The PtSA@VP-Ni3P-MoP performs a low overpotential of 28 and 261 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a current density of 10 and 25 mA cm-2, respectively. The PtSA@VP-Ni3P-MoP (+,-) alkaline electrolyzer achieves a minimum cell voltage of 1.48 V at a current density of 10 mA cm-2 for overall water splitting. Additionally, the electrocatalyst exhibits a substantial Faradaic yield of ≈98.12% for H2 and 98.47% for O2 at a current density of 50 mA cm-2. Consequently, this study establishes a connection for understanding the active role of single metal atoms in substrate configuration for catalytic performance. It also facilitates the successful synthesis of SACs, with a substantial loading on transition metal phosphides and maximal atomic utilization, providing more active sites and, thereby enhancing electrocatalytic activity.

Heterogeneous Ni-Boride/Phosphide Anchored Amorphous B-C Layer for Overall Water Electrocatalysis

The rational design of efficient and economical bifunctional electrocatalysts remained a challenge for overall water electrolysis. In this work, the Ni-boride/ phosphide particles anchored amorphous B-doped carbon layer with hierarchical porous characteristics in Ni foam (Ni3P/Ni3B/B-C/NF) was fabricated for overall water splitting. The Boroncarbide (B4C) power was filled and fixed in the NF interspace through the electroplating and electroless plating, and then annealed in vacuum high temperature. The amorphous B-C layer derived from the B4 C not only speeded up the electron transport, but also cooperate with Ni-boride/phosphide to enhance the electrocatalytic activity for HER and OER synergistically. Furthermore, the hierarchical porous architecture of Ni3P/Ni3B/B-C/NF increased space utilization to load more active materials. The self-supported Ni3P/Ni3B/B-C/NF electrode possessed a low overpotential of 212 and 280 mV to deliver 100 mA cm-2 for HER and OER, respectively, and high stability for 48 h. In particular, the electrolyzer constituted with the Ni3P/Ni3B/B-C/NF bifunctional electrocatalyst only required a voltage of 1.59 V at 50 mA cm-2 for water electrocatalysis under alkaline medium, and demonstrated long-term stability for 48 h. This study provides a new technical path for the development of bifunctional of transition metal borides to promote the application of hydrogen production from water splitting.

Recent Progress on Nickel- and Iron-Based Metallic Organic Frameworks for Oxygen Evolution Reaction: A Review

Developing sustainable energy solutions to safeguard the environment is a critical ongoing demand. Electrochemical water splitting (EWS) is a green approach to create effective and long-lasting electrocatalysts for the water oxidation process. Metal organic frameworks (MOFs) have become commonly utilized materials in recent years because of their distinguishing pore architectures, metal nodes easy accessibility, large specific surface areas, shape, and adaptable function. This review outlines the most significant developments in current work on developing improved MOFs for enhancing EWS. The benefits and drawbacks of MOFs are first discussed in this review. Then, some cutting-edge methods for successfully modifying MOFs are also highlighted. Recent progress on nickel (Ni) and iron (Fe) based MOFs have been critically discussed. Finally, a comprehensive analysis of the existing challenges and prospects for Ni- and Fe-based MOFs are summarized.

N, P co-doped Ni/Mo-based multicomponent electrocatalysts in situ decorated on Ni foam for overall water splitting

Developing the robust non-precious metal bifunctional electrocatalyst is highly imperative for the hydrogen evolution from overall water splitting. Herein, a Ni foam (NF)-supported ternary Ni/Mo bimetallic complex (Ni/Mo-TEC@NF), hierarchically constructed by coupling the in-situ formed MoNi₄ alloys and Ni₂Mo₃O₈ with Ni₃Mo₃C on NF, has been developed through a facile method involving the in-situ hydrothermal growth of the Ni-Mo oxides/polydopamine (NiMoO_x/PDA) complex on NF and a subsequent annealing in a reduction atmosphere. Synchronously, N and P atoms are co-doped into Ni/Mo-TEC during the annealing procedure using phosphomolybdic acid and PDA raw materials as P and N sources, respectively. The resultant N, P-Ni/Mo-TEC@NF shows outstanding electrocatalytic activities and tremendous stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), due to the multiple heterojunction effect-promoted electron transfer, the large number of exposed active sites, and the modulated electronic structure by the N and P co-doping. It only needs a low overpotential of 22 mV to afford the current density of 10 mA·cm^-2 for HER in alkaline electrolyte. More importantly, as the anode and cathode, it requires only 1.59 and 1.65 V to achieve 50 and 100 mA·cm^-2 for overall water splitting, respectively, comparable to the benchmark Pt/C@NF//RuO₂@NF couple. This work could spur the search for economical and efficient electrodes by in situ constructing multiple bimetallic components on 3D conductive substrates for practical hydrogen generation.

S-modified NiFe-phosphate hierarchical hollow microspheres for efficient industrial-level seawater electrolysis

For sustained hydrogen generation from seawater electrolysis, an efficient and specialized catalyst must be designed to cope with the slow anode reaction and chloride ions (Cl^-) corrosion. In this work, an S-modified NiFe-phosphate with hierarchical and hollow microspheres was grown on the NiFe foam skeleton (S-NiFe-Pi/NFF), acting as a bifunctional catalyst to enable industrial-scale seawater electrolysis. The introduction of S distorted the lattice of NiFe-phosphate and regulated the local electronic environment around Ni/Fe active metal, both of which enhanced the electrocatalytic activity. Additionally, the existence of phosphate groups repelled Cl^- on the surface and enhanced corrosion resistance, enabling stable long-term operation in seawater. The double-electrode electrolyzer composed of the hollow-structured S-NiFe-Pi/NFF as both cathode and anode exhibited a potential of 1.68 V at 100 mA cm^-2 for seawater electrolysis. Particularly, to achieve industrial requirements of 500 mA cm^-2, it only required a low cell voltage of 1.8 V and demonstrated a consistent response over 100 h, which outperformed the pair of Pt/C || IrO₂. This study provides a feasible idea for the preparation of electrocatalysts that are with both highly activity and corrosion resistance, which is crucial for the implementation of industrial-scale seawater electrolysis.

Vanadium-Based Trimetallic Metal-Organic-Framework Family as Extremely High-Performing and Ultrastable Electrocatalysts for Water Splitting

This is the first time that the pore-space-partition (PSP) strategy is being successfully applied in the electrochemical field for water splitting, realizing the highly efficient construction of a series of ultrastable pristine MOF electrocatalysts. On integrating the vanadium-based trimetallic building cluster (M₂V), the target M₂V-MOFs exhibit excellent electrocatalytic activity for HER, OER, and water splitting. In particular, ultralow overpotentials of 314 and 198 mV for Fe₂V-MOF as OER and HER electrocatalysts, respectively, can drive a current density of 10 mA cm^-2. The fabricated Fe₂V-MOF||Pt/C two-electrode configuration for the overall water splitting yields a current density of 10 mA cm^-2 at only 1.6 V vs RHE, which is superior to that of the commercial IrO₂||Pt/C couple. Notably, high structural and chemical stabilities still can be observed in alkaline condition. This work opens up an exciting pathway to design efficient and stable electrocatalysts based on pristine MOF by integrating the PSP strategy and multimetallic centers.

Topochemical Transformation of Two-Dimensional VSe2 into Metallic Nonlayered VO2 for Water Splitting Reactions in Acidic and Alkaline Media

The engineering of the structural and morphological properties of nanomaterials is a fundamental aspect to attain desired performance in energy storage/conversion systems and multifunctional composites. We report the synthesis of room temperature-stable metallic rutile VO₂ (VO₂ (R)) nanosheets by topochemically transforming liquid-phase exfoliated VSe₂ in a reductive Ar-H₂ atmosphere. The as-produced VO₂ (R) represents an example of two-dimensional (2D) nonlayered materials, whose bulk counterparts do not have a layered structure composed by layers held together by van der Waals force or electrostatic forces between charged layers and counterbalancing ions amid them. By pretreating the VSe₂ nanosheets by O₂ plasma, the resulting 2D VO₂ (R) nanosheets exhibit a porous morphology that increases the material specific surface area while introducing defective sites. The as-synthesized porous (holey)-VO₂ (R) nanosheets are investigated as metallic catalysts for the water splitting reactions in both acidic and alkaline media, reaching a maximum mass activity of 972.3 A g^-1 at -0.300 V vs RHE for the hydrogen evolution reaction (HER) in 0.5 M H₂SO₄ (faradaic efficiency = 100%, overpotential for the HER at 10 mA cm^-2 = 0.184 V) and a mass activity (calculated for a non 100% faradaic efficiency) of 745.9 A g^-1 at +1.580 V vs RHE for the oxygen evolution reaction (OER) in 1 M KOH (overpotential for the OER at 10 mA cm^-2 = 0.209 V). By demonstrating proof-of-concept electrolyzers, our results show the possibility to synthesize special material phases through topochemical conversion of 2D materials for advanced energy-related applications.

Electro- and photoelectro-catalysts derived from bimetallic amorphous metal–organic frameworks

It is developed a synthesis method for the design of new bimetallic amorphous MOFs. Such frameworks serve as precursors to prepare high-performance electro- and photoelectro-catalysts for ORR, OER and HER in both acidic and alkaline media.