Synthesis of a MoS x -O-PtO x Electrocatalyst with High Hydrogen Evolution Activity Using a Sacrificial Counter-Electrode

Mechanistic insights on Bi-potentiodynamic control towards atomistic synthesis of electrocatalysts for hydrogen evolution reaction

Herein, electrochemically assisted dissolution-deposition (EADD) is utilized over a three-electrode assembly to prepare an electrocatalyst for hydrogen evolution reaction (HER). Cyclic voltammetry is performed to yield atomistic loading of platinum (Pt) over SnS2 nanostructures via Pt dissolution from the counter electrode (CE). Astonishingly, the working electrode (WE) swept at 50 mV/s is found to compel Pt CE to experience 1000-3000 mV/s. The effect of different potential scan rates at the WE have provided insight into the change in Pt dissolution and its deposition behaviour over SnS2 in three electrode assembly. However, uncontrolled overpotentials at CE in a three-electrode assembly made Pt dissolution-deposition behavior complex. Here, for the first time, we have demonstrated bi-potentiodynamic control for dissolution deposition of Pt in four-electrode assembly over Nickel (Ni) foam. The dual cyclic voltammetry is applied to achieve better control and efficiency of the EADD process, engendering it as a pragmatically versatile and scalable synthesis technique.

In Situ Electrosynthesis of MAX-Derived Electrocatalysts for Superior Hydrogen Evolution Reaction

MAX phases are frequently dominated as precursors for the preparation of the star material MXene, but less eye-dazzling by their own potential applications. In this work, the electrocatalytic hydrogen evolution reaction (HER) activity of MAX phase is investigated. The MAX-derived electrocatalysts are prepared by a two-step in situ electrosynthesis process, an electrochemical etching step followed by an electrochemical deposition step. First, a Mo₂ TiAlC₂ MAX phase is electrochemically etched in 0.5 m H₂ SO₄ electrolyte. Just several hours, electrochemical dealloy etching of Mo₂ TiAlC₂ MAX powders by applying anode current can acquire a moderated HER performance, outperforming most of reported pure MXene. It is speculated that in situ superficially architecting endogenous MAX/amorphous carbide (MAC) improves its intrinsic catalytic activity. Subsequently, highly active metallic Pt nanoparticles immobilized on MAC (MAC@Pt) shows a transcendental overpotential of 40 mV versus RHE in 0.5 m H₂ SO₄ and 79 mV in 1.0 m KOH at the current density of 10 mA cm^-2 without iR correction. Ultrahigh mass activity of MAC@Pt (1.5 A mg_pt ^-1 ) at 100 mV overpotential is also achieved, 29-folds than those of commercial PtC catalysts.

Atomic Structural Evolution of Single-Layer Pt Clusters as Efficient Electrocatalysts

The rational synthesis of single-layer noble metal directly anchored on support materials is an elusive target to accomplish for a long time. This paper reports well-defined single-layer Pt (Pt-SL) clusters anchored on ultrathin TiO₂ nanosheets-as a new frontier in electrocatalysis. The structural evolution of Pt-SL/TiO₂ via self-assembly of single Pt atoms (Pt-SA) is systematically recorded. Significantly, the Pt atoms of Pt-SL/TiO₂ possess a unique electronic configuration with PtPt covalent bonds surrounded by abundant unpaired electrons. This Pt-SL/TiO₂ catalyst presents enhanced electrochemical performance toward diverse electrocatalytic reactions (such as the hydrogen evolution reaction and the oxygen reduction reaction) compared with Pt-SA, multilayer Pt nanoclusters, and Pt nanoparticles, suggesting an efficient new type of catalyst that can be achieved by constructing single-layer atomic clusters on supports.

An Overview on Noble Metal (Group VIII)-based Heterogeneous Electrocatalysts for Nitrogen Reduction Reaction

The typically the Haber-Bosch process of nitrogen (N₂ ) reduction to ammonia (NH₃ ) production, expends a lot of energy, resulting in severe environmental issues. Electro-catalytic N₂ reduction to NH₃ formation by renewable resources is one of the effective ways to settle the issue. However, the electro-catalytic performances and selectivity of catalysts for electrochemical nitrogen reduction reaction (NRR) are very low. Therefore, it is of great significance to develop more efficient electro-catalysts to satisfy the needs of practical use. Among the reported catalysts, those based on Group VIII noble metals heterogeneous catalysts display excellent NRR activities and high selectivity because of their good conductivity, rich active surface area, unfilled d-orbitals, and the abilities with easy adsorption of reactants and stable reaction intermediates. Herein, we will introduce the progress of Group VIII precious metals heterogeneous catalysts applied in the electrocatalytic N₂ reduction reaction. Then single precious metal electrocatalysts, precious metal alloy electrocatalysts, heterojunction structure electrocatalysts, and precious metal compounds based on the strategies of morphology engineering, crystal facet engineering, defect engineering, heteroatom doping, and synergetic interface engineering will be discussed. Finally, the challenges and prospects of the NH₃ synthesis have been put forward. In the review, we will provide helpful direction to the development of effective electro-catalysts for catalytic N₂ reduction reaction.

Fabrication of hierarchical SrTiO3@MoS2 heterostructure nanofibers as efficient and low-cost electrocatalysts for hydrogen-evolution reactions

The construction of low-cost, high-performance electrocatalysts instead of platinum catalysts is critical to solving the energy crisis. Here, using simple electrospinning and hydrothermal methods, new MoS₂ nanosheets on SrTiO₃ nanofibers (NFs) and 2D SrTiO₃@MoS₂ heterostructure NFs are synthesized. In addition, SrTiO₃@MoS₂ heterostructure NFs are compared with bare SrTiO₃ NFs and MoS₂ nanosheets. Importantly, the prepared SrTiO₃@MoS₂ heterostructure shows better hydrogen-evolution reaction performance than other MoS₂-based electrocatalysts with an overpotential of 165 mV at 10 mA cm^-2, a Tafel slope of 81.41 mV dec^-1, and long-term electrochemical durability of 3000 cycles. Therefore, the present work strongly demonstrates the positive synergy between SrTiO₃ NFs and layered MoS₂, and also provides a strategy for preparing low-cost and high-activity water-decomposition electrocatalysts.

Pt-O bond as an active site superior to Pt0 in hydrogen evolution reaction

The oxidized platinum (Pt) can exhibit better electrocatalytic activity than metallic Pt⁰ in the hydrogen evolution reaction (HER), which has aroused great interest in exploring the role of oxygen in Pt-based catalysts. Herein, we select two structurally well-defined polyoxometalates Na₅[H₃Pt^(IV)W₆O₂₄] (PtW₆O₂₄) and Na₃K₅[Pt^(II)₂(W₅O₁₈)₂] (Pt₂(W₅O₁₈)₂) as the platinum oxide model to investigate the HER performance. Electrocatalytic experiments show the mass activities of PtW₆O₂₄/C and Pt₂(W₅O₁₈)₂/C are 20.175 A mg⁻¹ and 10.976 A mg⁻¹ at 77 mV, respectively, which are better than that of commercial 20% Pt/C (0.398 A mg⁻¹). The in situ synchrotron radiation experiments and DFT calculations suggest that the elongated Pt-O bond acts as the active site during the HER process, which can accelerate the coupling of proton and electron and the rapid release of H₂. This work complements the knowledge boundary of Pt-based electrocatalytic HER, and suggests another way to update the state-of-the-art electrocatalyst.

While converting water to H₂ with a catalyst offers a renewable means to produce carbon-neutral fuels, understanding the catalytic active sites has proven challenging. Here, authors show a structurally well-defined model complex with Pt-O bonding to enable efficient H₂ evolution electrocatalysis.