Strained few-layer MoS2 with atomic copper and selectively exposed in-plane sulfur vacancies for CO2 hydrogenation to methanol

Interfacial Engineering of MoS2@CoS2 Heterostructure Electrocatalysts for Effective pH-Universal Hydrogen Evolution Reaction

The practical utilization of the hydrogen evolution reaction (HER) necessitates the creation of electrocatalysts that are both efficient and abundant in earth elements, capable of operating effectively within a wide pH range. However, this objective continues to present itself as an arduous obstacle. In this research, we propose the incorporation of sulfur vacancies in a novel heterojunction formed by MoS2@CoS2, designed to exhibit remarkable catalytic performances. This efficacy is attributed to the advantageous combination of the low work function and space charge zone at the interface between MoS2 and CoS2 in the heterojunction. The MoS2@CoS2 heterojunction manifests outstanding hydrogen evolution activity over an extensive pH range. Remarkably, achieving a current density of 10 mA cm-2 in aqueous solutions 1.0 M KOH, 0.5 M H2SO4, and 1.0 M phosphate-buffered saline (PBS), respectively, requires only an overpotential of 48, 62, and 164 mV. The Tafel slopes for each case are 43, 32, and 62 mV dec-1, respectively. In this study, the synergistic effect of MoS2 and CoS2 is conducive to electron transfer, making the MoS2@CoS2 heterojunction show excellent electrocatalytic performance. The synergistic effects arising from the heterojunction and sulfur vacancy not only contribute to the observed catalytic prowess but also provide a valuable model and reference for the exploration of other efficient electrocatalysts. This research marks a significant stride toward overcoming the challenges associated with developing electrocatalysts for practical hydrogen evolution applications.

Application of metal-organic frameworks and their derivates for thermal-catalytic C1 molecules conversion

One-carbon (C1) catalysis refers to the conversion of compounds with a single carbon atom, especially carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4), into clean fuels and valuable chemicals via catalytic strategy is crucial for sustainable and green development. Among various catalytic strategies, thermal-driven process seems to be one of the most promising pathways for C1 catalysis due to the high efficiency and practical application prospect. Notably, the rational design of thermal-driven C1 catalysts plays a vital role in boosting the targeted products synthesis of C1 catalysis, which relies heavily on the choice of ideal active site support, catalyst fabrication precursor, and catalytic reaction field. As a novel crystalline porous material, metal-organic frameworks (MOFs) has made significant progress in the design and synthesis of various functional nanomaterials. However, the application of MOFs in C1 catalysis faces numerous challenges, such as thermal stability, mechanical strength, yield of MOFs, and so on. To overcome these limitations and harness the advantages of MOFs in thermal-driven C1 catalysis, researchers have developed various catalyst/carrier preparation strategies. In this review, we provide a concise overview of the recent advancements in the conversion of CO, CO2, and CH4 into clean fuels and valuable chemicals via thermal-catalytic strategy using MOFs-based catalysts. Furthermore, we discuss the main challenges and opportunities associated with MOFs-based catalysts for thermal-driven C1 catalysis in the future.

In Situ Carbon-Confined MoSe2 Catalyst with Heterojunction for Highly Selective CO2 Hydrogenation to Methanol

The synthesis of methanol from CO2 hydrogenation is an effective measure to deal with global climate change and an important route for the chemical fixation of CO2. In this work, carbon-confined MoSe2 (MoSe2@C) catalysts were prepared by in situ pyrolysis using glucose as a carbon source. The physico-chemical properties and catalytic performance of CO2 hydrogenation to yield methanol were compared with MoSe2 and MoSe2/C. The results of the structure characterization showed MoSe2 displayed few layers and a small particle size. Owing to the synergistic effect of the Mo2C-MoSe2 heterojunction and in situ carbon doping, MoSe2@C with a suitable C/Mo mole ratio in the precursor showed excellent catalytic performance in the synthesis of methanol from CO2 hydrogenation. Under the optimal catalyst MoSe2@C-55, the selectivity of methanol reached 93.7% at a 9.7% conversion of CO2 under optimized reaction conditions, and its catalytic performance was maintained without deactivation during a continuous reaction of 100 h. In situ diffuse infrared Fourier transform spectroscopy studies suggested that formate and CO were the key intermediates in CO2 hydrogenation to methanol.

Atomically Precise Mo2Cu17 Bimetallic Nanocluster: Synergistic Mo2O4-Coupled Copper Alkynyl Cluster for the Improved Hydrogen Evolution Reaction Performance

Electrolytic hydrogen production via water splitting holds significant promise for the future of the energy revolution. The design of efficient and abundant catalysts, coupled with a comprehensive understanding of the hydrogen evolution reaction (HER) mechanism, is of paramount importance. In this study, we propose a strategy to craft an atomically precise cluster catalyst with superior HER performance by cocoupling a Mo2O4 structural unit and a Cu(I) alkynyl cluster into a structured framework. The resulting bimetallic cluster, Mo2Cu17, encapsulates a distinctive structure [Mo2O4Cu17(TC4A)4(PhC≡C)6], comprising a binuclear Mo2O4 subunit and a {Cu17(TC4A)2(PhC≡C)6} cluster, both shielded by thiacalix[4]arene (TC4A) and phenylacetylene (PhC≡CH). Expanding our exploration, we synthesized two homoleptic CuI alkynyl clusters coprotected by the TC4A and PhC≡C- ligands: Cu13 and Cu22. Remarkably, Mo2Cu17 demonstrates superior HER efficiency compared to its counterparts, achieving a current density of 10 mA cm-2 in alkaline solution with an overpotential as low as 120 mV, significantly outperforming Cu13 (178 mV) and Cu22 (214 mV) nanoclusters. DFT calculations illuminate the catalytic mechanism and indicate that the intrinsically higher activity of Mo2Cu17 may be attributed to the synergistic Mo2O4-Cu(I) coupling.

Boosting CO2 Hydrogenation to Methanol over Monolayer MoS2 Nanotubes by Creating More Strained Basal Planes

The controlled creation, selective exposure, and activation of more basal planes while simultaneously minimizing the generation and exposure of edge sites are crucial for accelerating methanol synthesis from CO2 hydrogenation over MoS2 catalysts but remain a bottleneck. Here, we report a facile method to fabricate heteronanotube catalysts with single-layer MoS2 coaxially encapsulating the carbon nanotubes (CNTs@MoS2) through host-guest chemistry. Inheriting the long tubular structure of CNTs, the grown MoS2 nanotubes exhibit significantly more basal planes than bulk MoS2 crystals. More importantly, the tubular curvature not only promotes strain and sulfur vacancy (Sv) generation but also preferentially exposes more in-plane Sv while limiting edge Sv exposure, which is conducive to methanol synthesis. Both the strain and layer number of MoS2 can be easily and finely adjusted by altering CNT diameter and quantity of precursors. Remarkably, CNTs@MoS2 with monolayer MoS2 and maximum strain displayed methanol selectivity of 78.1% and methanol space time yield of 1.6 g gMoS2-1 h-1 at 260 °C and GHSV of 24000 mL gcat.-1 h-1, representing the best results to date among Mo-based catalysts. This study provides prospects for novel catalyst design by synthesizing coaxial tubular heterostructure to create additional catalytic sites and ultimately enhance conversion and selectivity.

Mn-promoted MoS2 catalysts for CO2 hydrogenation: enhanced methanol selectivity due to MoS2/MnOx interfaces

Considering the alarming scenario of climate change, CO2 hydrogenation to methanol is considered a key process for phasing out fossil fuels by means of CO2 utilization. In this context, MoS2 catalysts have recently shown to be promising catalysts for this reaction, especially in the presence of abundant basal-plane sulfur vacancies and due to synergistic mechanisms with other phases. In this work, Mn-promoted MoS2 prepared by a hydrothermal method presents considerable selectivity for CO2 hydrogenation to methanol in comparison with pure MoS2 and other promoters such as K and Co. Interestingly, if CO is used as a carbon source for the reaction, methanol production is remarkably lower, which suggests the absence of a CO intermediate during CO2 hydrogenation to methanol. After optimization of synthesis parameters, a methanol selectivity of 64% is achieved at a CO2 conversion of 2.8% under 180 °C. According to material characterization by X-ray Diffraction and X-ray Absorption, the Mn promoter is present mainly in the form of MnO and MnCO3 phases, with the latter undergoing convertion to MnO upon H2 pretreatment. However, following exposure to reaction conditions, X-ray photoelectron spectroscopy suggests that higher oxidation states of Mn may be present at the surface, suggesting that the improved catalytic activity for CO2 hydrogenation to methanol arises from a synergy between MoS2 and MnOx at the catalyst surface.

A twisted carbonaceous nanotube as the air-electrode for flexible Zn-Air batteries

Exploring electrocatalysts with high-efficiency oxygen reduction reaction (ORR) is significant for practical applications of fuel cells and metal-air batteries. In this work, a twisted core@shell material has been prepared with helical polypyrrole nanotubes (HPPys) as the core and coordination polymers (CPs) as the shell. After the pyrolysis process, a dense twisted carbon layer was formed by the reaction of CP and HPPy at its interface under Ar. The derived twisted carbonaceous nanotube exhibits good performance in both electrocatalytic ORR and OER. When used as the air-electrode in a flexible Zn-air battery, the battery shows good performance and stability.