NiTe2 Nanowire Outperforms Pt/C in High-Rate Hydrogen Evolution at Extreme pH Conditions

A tri-functional self-supported electrocatalyst featuring mostly NiTeO3 perovskite for H2 production via methanol-water co-electrolysis

A self-supported NiTeO3 perovskite is made by deploying an extended hydrothermal tellurization strategy with a restricted Te content, which was found to be exceptionally active towards the oxidation of water and methanol and the reduction of water in 1.0 M KOH where it delivered -10 mA cm-2 at just -1.54 V for a full cell featuring MOR‖HER.

Recent Advances in Transition Metal Tellurides (TMTs) and Phosphides (TMPs) for Hydrogen Evolution Electrocatalysis

The hydrogen evolution reaction (HER) is a developing and promising technology to deliver clean energy using renewable sources. Presently, electrocatalytic water (H₂O) splitting is one of the low-cost, affordable, and reliable industrial-scale effective hydrogen (H₂) production methods. Nevertheless, the most active platinum (Pt) metal-based catalysts for the HER are subject to high cost and substandard stability. Therefore, a highly efficient, low-cost, and stable HER electrocatalyst is urgently desired to substitute Pt-based catalysts. Due to their low cost, outstanding stability, low overpotential, strong electronic interactions, excellent conductivity, more active sites, and abundance, transition metal tellurides (TMTs) and transition metal phosphides (TMPs) have emerged as promising electrocatalysts. This brief review focuses on the progress made over the past decade in the use of TMTs and TMPs for efficient green hydrogen production. Combining experimental and theoretical results, a detailed summary of their development is described. This review article aspires to provide the state-of-the-art guidelines and strategies for the design and development of new highly performing electrocatalysts for the upcoming energy conversion and storage electrochemical technologies.

Facile hydrothermal synthesis of layered 1T′ MoTe2 nanotubes as robust hydrogen evolution electrocatalysts

Layered transition metal dichalcogenides (TMDs), such as molybdenum ditelluride (MoTe₂), have attracted much attention because of their novel structure-related physicochemical properties. In particular, semi-metallic-phase MoTe₂ (1T′) is considered as a competitive candidate for low-cost electrocatalysts for water splitting. However, there are few reports on the simple hydrothermal synthesis of MoTe₂ nanostructures compared with other layered TMDs. In this study, a facile one-step hydrothermal process was developed for the fabrication of layered MoTe₂, in which uniform nanotubes with a few layers of 1T′ MoTe₂ were fabricated at a lower temperature for the first time. The as-obtained MoTe₂ nanotubes were fully characterized using different techniques, which revealed their structure and indicated the presence of layered 1T′ nanocrystals. The efficient activity of MoTe₂ nanotubes for the electrocatalytic hydrogen evolution reaction (HER) in 0.5 M H₂SO₄ was demonstrated by the small Tafel slope of 54 mV/dec⁻¹ and endurable ability, which is attributed to the abundant active sites and remarkable conductivity of 1T′ MoTe₂ with a few-layer feature. This provides a facile method for the design and construction of efficient layered MoTe₂ based electrocatalysts.

Anchoring Highly Dispersed Pt Electrocatalysts on TiOx with Strong Metal-Support Interactions via an Oxygen Vacancy-Assisted Strategy as Durable Catalysts for the Oxygen Reduction Reaction

Pt electrocatalysts with high activity and durability have still crucial issues for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). In this study, a novel catalyst consisting of Pt nanoparticles (NPs) on TiO_x/C composites (TiO_x-V_o-H/C) with abundant oxygen vacancies (V_o) is proposed, which is abbreviated as PTO-V_o-H/C. The introduction of V_o helps anchor highly dispersed Pt NPs with low loading and strengthen the strong metal-support interaction (SMSI), which benefits to the enhanced ORR catalytic activity. Moreover, the accelerated durability test (ADT) demonstrates the higher retention of ORR activity for PTO-V_o-H/C. Experimental and theoretical analyses reveal that electronic interactions between Pt NPs and TiO_x/C composite support give rise to an electron-rich Pt NPs and strong SMSI effect, which is favorable for the electron transfer and stabilization of Pt NPs. More importantly, the assembled PEMFC with PTO-V_o-H/C shows only 6.9% of decay on maximum power density after 3000 ADT cycles while the performance of Pt/C sharply decreased. This work provides a new insight into the unique vacancy regulation of dispersive Pt on metal oxides for superior ORR performance.

Realizing Efficient Catalytic Performance and High Selectivity for Oxygen Reduction Reaction on a 2D Ni2SbTe2 Monolayer

One of the immediate challenges for the large-scale commercialization of hydrogen-based fuel cells is to develop cost-effective electrocatalysts to enable cathodic oxygen reduction reaction (ORR). Herein, we focus on the potential of the two-dimensional (2D) ternary chalcogenide Ni₂SbTe₂ monolayer as a high-performance electrocatalyst for the ORR using density function theory. Our computed results reveal that there are an obvious hybridization and electron transfer between the O 2p and Te 5p orbitals, which can activate the adsorbed oxygen and trigger the whole ORR process, with an overpotential as low as 0.33 V. In addition, the adsorption capacity of the monolayer surface for oxygen molecules can be effectively enhanced by doping with Fe or Co atoms. The Ni₂SbTe₂ monolayers doped with Fe or Co atoms not only maintain their original excellent ORR catalytic activity but also improve selectivity toward the four-electron (4e) reduction pathway. We highly anticipate that this work can provide excellent candidates and new ideas for designing low-cost and high-performance ORR catalysts to replace noble metal Pt-based catalysts in fuel cells.

Hierarchical Co3(PO4)2/CuI/g-CnH2n-2 S-Scheme Heterojunction for Efficient Photocatalytic Hydrogen Evolution

Graphdiyne (GD), a new type of carbon allotrope formed by sp and sp² hybrid carbon atoms, has attracted wide attention due to its high π-conjugation degree, special band structure, and uniformly distributed pores. In traditional synthesis methods, hexaethylbenzene was coupled on the substrate catalytic material (copper foil or foamed copper) to generate graphdiyne. In this work, CuI was used as the substrate catalytic material, and the CuI-GD composite was synthesized by cross-coupling in the pyridine solution of hexaethylbenzene. For the first time, Co₃(PO₄)₂ was modified by the CuI-GD composite material to prepare a Co₃(PO₄)₂/CuI-GD S-scheme heterojunction catalyst, which avoided the complicated process of removing the substrate catalytic material. Under the action of the internal electric field, electrons are induced to move quickly and directionally, and the powerful photogenerated electrons in the conduction band (CB) of GD and the holes in the valence band (VB) of CuI are retained to participate in the photocatalytic reaction. These advantages were combined with the high-energy acetylene bond in GD, which accelerated the catalytic reaction of the Co₃(PO₄)₂/CuI-GD heterostructure. Electrochemical and fluorescence analysis showed that Co₃(PO₄)₂/CuI-GD has faster electron and hole separation efficiency, lower hydrogen evolution overpotential, and higher carrier utilization. Therefore, Co₃(PO₄)₂/CuI-GD exhibited good hydrogen evolution activity. This work shows that GD has broad prospects in designing high-performance photocatalyst systems.

Au-Cu2-xTe Plasmonic Heteronanostructure Photoelectrocatalysts

Semiconductor nanocrystals coupled with plasmonic Au nanoparticles have been widely studied as photoelectrocatalysts for solar water splitting. Among these, heterostructures of copper chalcogenides with Au remained a unique category for their dual plasmon character. However, while sulfides and selenides of copper have been extensively reported, heterostructures of copper tellurides with Au have not been explored. Herein, the plasmonic semiconductor Cu_2-xTe disks grown on Au nanoparticles (disk-on-dot) were explored as efficient photoelectrocatalysts for hydrogen evolution reactions (HER). This has been successfully designed by growing Cu_2-xTe disks on presynthesized Au nanoparticles under optimized reaction conditions. The resulting heterostructured nanocrystals acted as efficient photoelectrocatalysts for the H₂ evolution reaction with a low Tafel slope and less cathodic overpotential in the presence of light. Details of their synthesis, characterization, optical properties, and electrocatalytic activities are studied and reported in this letter.

Molecular Main Group Metal Hydrides

This review serves to document advances in the synthesis, versatile bonding, and reactivity of molecular main group metal hydrides within Groups 1, 2, and 12-16. Particular attention will be given to the emerging use of said hydrides in the rapidly expanding field of Main Group element-mediated catalysis. While this review is comprehensive in nature, focus will be given to research appearing in the open literature since 2001.

Strategies and Perspectives to Catch the Missing Pieces in Energy-Efficient Hydrogen Evolution Reaction in Alkaline Media

Transition metal hydroxides (M-OH) and their heterostructures (X|M-OH, where X can be a metal, metal oxide, metal chalcogenide, metal phosphide, etc.) have recently emerged as highly active electrocatalysts for hydrogen evolution reaction (HER) of alkaline water electrolysis. Lattice hydroxide anions in metal hydroxides are primarily responsible for observing such an enhanced HER activity in alkali that facilitate water dissociation and assist the first step, the hydrogen adsorption. Unfortunately, their poor electronic conductivity had been an issue of concern that significantly lowered its activity. Interesting advancements were made when heterostructured hydroxide materials with a metallic and or a semiconducting phase were found to overcome this pitfall. However, in the midst of recently evolving metal chalcogenide and phosphide based HER catalysts, significant developments made in the field of metal hydroxides and their heterostructures catalysed alkaline HER and their superiority have unfortunately been given negligible attention. This review, unlike others, begins with the question of why alkaline HER is difficult and will take the reader through evaluation perspectives, trends in metals hydroxides and their heterostructures catalysed HER, an understanding of how alkaline HER works on different interfaces, what must be the research directions of this field in near future, and eventually summarizes why metal hydroxides and their heterostructures are inevitable for energy-efficient alkaline HER.

Solvent-Free Mechanochemical Synthesis and Characterization of Nickel Tellurides with Various Stoichiometries: NiTe, NiTe2 and Ni2Te3

The paper reports the synthesis of nickel tellurides via a mechanochemical method from elemental precursors. NiTe, NiTe₂, and Ni₂Te₃ were prepared by milling in stainless steel vials under nitrogen, using milling times from 1 h to 12 h. The products were characterized by powder X-ray diffraction (pXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), vibrating sample magnetometer (VSM), UV-VIS spectrometry, and thermal analysis (TGA and DSC). The products were obtained in the form of aggregates, several hundreds of nanometers in size, consisting of smaller nanosized crystallites. The magnetic measurements revealed a ferromagnetic behavior at room temperature. The band gap energies calculated using Tauc plots for NiTe, NiTe₂, and Ni₂Te₃ were 3.59, 3.94, and 3.70 eV, respectively. The mechanochemical process has proved to be a simple and successful method for the preparation of binary nickel tellurides, avoiding the use of solvents, toxic precursors, and energy-consuming reaction conditions.

Few-Layer Tellurium: Cathodic Exfoliation and Doping for Collaborative Hydrogen Evolution

2D tellurium is a suitable electrocatalyst support that can assist electron transport while hosting active sites, yet its production remains challenging. Herein, a cathodic exfoliation method that can exfoliate Te crystal directly to Te nanosheets at low potential, also enabling simultaneous transition metal doping on Te nanosheet surface is presented. In situ Raman spectra and ex situ characterizations reveal that the cathodic exfoliation relies on the electrostatic repulsion between Te flakes covered with in situ generated ditelluride (Te₂ ^2- ) anions. The Te₂ ^2- anions can anchor metal ions to the surface, and the doping concentration can be tuned by adjusting the concentration of metal ion in the electrolyte. The metal-doped Te nanosheets exhibit highly improved hydrogen evolution activities. In particular, Pt-doped Te outperforms polycrystalline Pt at high overpotential. A collaborative hydrogen production mechanism via Volmer-Heyrovsky pathway is suggested: Te₂ ^2- adsorbs protons and assists the mass transfer to adjacent Pt atoms where the protons are reduced and released as hydrogen.

A review on recent developments in electrochemical hydrogen peroxide synthesis with a critical assessment of perspectives and strategies

Electrochemical hydrogen peroxide synthesis using two-electron oxygen electrochemistry is an intriguing alternative to currently dominating environmentally unfriendly and potentially hazardous anthraquinone process and noble metals catalysed direct synthesis. Electrocatalytic two-electron oxygen reduction reaction (ORR) and water oxidation reaction (WOR) are the source of electrochemical hydrogen peroxide generation. Various electrocatalysts have been used for the same and were characterized using several electroanalytical, chemical, spectroscopic and chromatographic tools. Though there have been a few reviews summarizing the recent developments in this field, none of them have unified the approaches in catalysts' design, criticized the ambiguities and flaws in the methods of evaluation, and emphasized the role of electrolyte engineering. Hence, we dedicated this review to discuss the recent trends in the catalysts' design, performance optimization, evaluation perspectives and their appropriateness and opportunities with electrolyte engineering. In addition, particularized discussions on fundamental oxygen electrochemistry, additional methods for precise screening, and the role of solution chemistry of synthesized hydrogen peroxide are also presented. Thus, this review discloses the state-of-the-art in an unpresented view highlighting the challenges, opportunities, and alternative perspectives.

Ultrafast Growth of a Cu(OH)2-CuO Nanoneedle Array on Cu Foil for Methanol Oxidation Electrocatalysis

A swift potentiostatic anodization method for growing a 5-7 μm tall nanoneedle array of Cu(OH)₂-CuO on Cu foil within 100 s has been developed. This catalytic electrode when screened for methanol oxidation electrocatalysis in 1 M KOH with 0.5 M methanol, delivered a current density as high as 70 ± 10 mA cm^-2 at 0.65 V versus Hg/HgO which is superior to the performance of many related catalysts reported earlier. The observed activity enhancement is attributed to the formation of both Cu(OH)₂-CuO nanoneedle arrays of high active surface area over the metallic Cu foil. In addition, the Cu(OH)₂-CuO/Cu electrode had also exhibited excellent stability upon prolonged potentiostatic electrocatalytic oxidation of methanol while retaining the charge-transfer characteristics. Growth of such highly ordered assembly of Cu(OH)₂-CuO nanoneedles within a minute has never been achieved before. When compared to its oxygen evolution reaction activity, the addition of 0.5 M methanol has lowered the overpotential at 10 mA cm^-2 by 334 mV, which is significant. This encourages the use of methanol as a sacrificial anolyte for energy-saving production of H₂ from water electrolysis.

The shape-controlled synthesis of gallium-palladium (GaPd2) nanomaterials as high-performance electrocatalysts for the hydrogen evolution reaction

Recently, great efforts have been focused on developing more active and stable Pd-based electrocatalysts to partially or completely replace rare and costly Pt. We developed a facile hot injection method and successfully synthesized well-dispersed and shape-controlled GaPd2 nanomaterials including polyhedrons, nanoparticles and nanowires. All the as-synthesized catalysts exhibit superior HER activity compared to commercial pure Pd catalysts and are stable in acidic media. Among them, the GaPd2 nanoparticles required only 24.3 mV overpotential to achieve a 10 mA cm-2 current density, which is outstanding compared to most Pt-based nanomaterials. Also, cycling tests over 10 000 CV sweep cycles (-0.3 to 0.2 vs. RHE) and durability testing for 24 hours were applied, with the GaPd2 catalysts exhibiting similar i-V curves and stable current densities to those obtained in the initial tests. We further evaluated the mass activities of the GaPd2 catalysts, and it is fascinating that the GaPd2 polyhedrons, nanoparticles and nanowires achieved factors of 3.7, 5 and 2.3 enhancement in mass activity at -0.1 V vs. RHE compared with a commercial Pd black catalyst. Meanwhile, with the assistance of a reduced graphene oxide (rGO) support, the GaPd2 nanoparticles/rGO (20 wt%) electrocatalyst presents outstanding HER activity comparable with that of a carbon-supported Pt catalyst (20% Pt/C). This work provides an avenue to develop effective and stable Pd-based catalysts with reduced Pd usage and high HER performance.

An Fe-doped NiTe bulk crystal as a robust catalyst for the electrochemical oxygen evolution reaction

An Fe doped NiTe bulk crystal was demonstrated to exhibit an extremely active and stable performance for the electrochemical oxygen evolution reaction.