Guest ions pre-intercalation strategy of manganese-oxides for supercapacitor and battery applications

https://onlinelibrary.wiley.com/doi/pdf/10.1002/sstr.202100076

Electrocatalytic Hydrogen Evolution Reaction Related to Nanochannel Materials

Selectivity Origin of Organic Electrosynthesis Controlled by Electrode Materials: A Case Study on Pinacols

In situ construction of γ-MoC/VN heterostructured electrocatalysts with strong electron coupling for highly efficient hydrogen evolution reaction

Electrochemical hydrogenation (ECH) is a particularly important and environmentally friendly approach to obtain biomass-based fuels and high value-added fine chemicals without using external hydrogen. Herein, we reported a highly efficient and selective ECH of furfural (FF) into furfuryl alcohol (FA) with Cu-based electrocatalyst in aqueous alkaline media. Under the optimal conditions, FA selectivity close to 100% with 99% FF conversion and total Faradaic efficiency above 95% were obtained with the electrocatalyst. Mechanism investigation suggests an ECH mechanism for FA formation, which is highly potential-dependent to FA selectivity, requiring low and well-matched concentrations between active hydrogen (Hads) species and FA radical on the Cu surface. Moreover, the electrocatalyst shows an excellent stability and recyclability during the eight-time consecutive recycling experiments, yielding a total amount of 1011 mg FA. This work thus highlights an important guidance for electrocatalytic upgrading of biomass-based platform molecules in an environmentally friendly way. 

Electrochemical Hydrogenation of Biomass-based Furfural in Aqueous Media by Cu Catalyst Supported on N-doped Hierarchically Porous Carbon

Electrocatalytic hydrogenation (ECH) enables the sustainable production of chemicals under ambient condition; however, suffers from serious competition with hydrogen (H2) evolution and the use of precious metals as electrocatalysts. Herein, molybdenum disulfide is for the first time developed as an efficient and noble-metal-free catalyst for ECH via in situ intercalation of ammonia or alkyl-amine cations. This interlayer engineering regulates phase transition (2H → 1 T), and effectively ameliorates electronic configurations and surface hydrophobicity to promote the ECH of biomass-derived oxygenates, while prohibiting H2 evolution. The optimal one intercalated by dimethylamine (MoS2-DMA) is capable of hydrogenating furfural (FAL) to furfuryl alcohol with high Faradaic efficiency of 86.3%–73.3% and outstanding selectivity of >95.0% at −0.25 to −0.65 V (vs. RHE), outperforming MoS2 and other conventional metals. Such prominent performance stems from the enhanced chemisorption and surface hydrophobicity. The chemisorption of H intermediate and FAL, synchronously strengthened on the edge-sites of MoS2-DMA, accelerates the surface elementary step following Langmuir-Hinshelwood mechanism. Moreover, the improved hydrophobicity benefits FAL affinity to overcome diffusion limitation. Discovering the effective modulation of MoS2 from a typical H2 evolution electrocatalyst to a promising candidate for ECH, this study broadens the scope to exploit catalysts used for electrochemical synthesis.

Interlayer engineering of molybdenum disulfide toward efficient electrocatalytic hydrogenation

An efficient electrocatalyst of molybdenum carbide nanodots on carbon nanosheets (nano-MoC/C-Ns) is prepared via a novel interlayer-confined strategy with the aid of MCM-22(P), a kind of multilayered two-dimensional (2D) zeolite precursor. In this strategy, the confined space of the surfactant-swollen MCM-22(P) plays a critical role in creating a unique sandwich-like structure with Mo-based organic–inorganic nanohybrids which further in situ evolve into ultrafine ∼2 nm MoC nanodots on carbon nanosheets in the following carbonization process. After etching the zeolite layers, the nano-MoC/C-Ns is successfully obtained as an efficient noble-metal-free electrocatalyst for hydrogen evolution. The intimate contact between ultrafine MoC nanodots and C nanosheets, as well as their synergetic effects, endows this catalyst with large exposed active sites and accelerated electron transport. The optimal sample achieves excellent hydrogen evolution reaction performance in acidic, neutral and alkaline media with low η10 values of 126, 185 and 92 mV (vs. the values of 28, 36 and 37 mV for a Pt/C reference in acidic, neutral and alkaline media), respectively. This synthetic strategy provides some hints for designing high-performance carbides for energy conversion and storage.

MoC nanodots toward efficient electrocatalytic hydrogen evolution: an interlayer-confined strategy with a 2D-zeolite precursor

Chinese ink-promoted co-assembly synthesis of 3D hierarchically structured and porous MoCx/C nanocomposites for highly efficient hydrogen evolution reaction

Molybdenum carbides (MoxC) are regarded as low-cost non-noble metal electrocatalysts for the hydrogen evolution reaction (HER). However, most reported powdery MoxC materials suffer from several drawbacks of polymer binders (such as Nafion) including partial blocking of active sites and decreased long-term stability. The recently developed binder-free MoxC materials are based on pre-treated commercial current-collecting substrates such as carbon cloth and carbon fibers, which make it basically impossible to design hierarchical porosity and achieve uniform distribution of active sites. Herein, we successfully synthesized self-supporting binder-free Mo2C composited electrocatalytic materials by integrating Mo2C nanoparticles with three-dimensional (3D) hierarchical porous carbon monoliths (PCMs) via a facile impregnation followed by in situ carbonization treatment (denoted as 3D Mo2C/PCM). As a result, Mo2C nanoparticles of ∼5 nm were uniformly distributed on the in situ transformed carbon matrix, and their uniform macropores (∼9 μm) and open ordered mesopores (5.6 nm) guaranteed fast mass transport and full exposure of active sites. The optimal 3D Mo2C/PCM sample displayed overpotentials of 81 and 47 mV at 10 mA cm−2 in 0.5 M H2SO4 and 1.0 M KOH, respectively, and the corresponding Tafel slopes were 63 and 45 mV dec−1. Benefiting from the outstanding mechanical strength and the easy-to-adjust macromorphology, 3D Mo2C/PCM could be directly used as a self-supporting working electrode without adding any binders. The synthesis strategy in this work may be extended to fabricate other bulky self-supporting carbon-based catalysts.

Haiyang Lu

Papers

Interlayer engineering of molybdenum disulfide toward efficient electrocatalytic hydrogenation

MoC nanodots toward efficient electrocatalytic hydrogen evolution: an interlayer-confined strategy with a 2D-zeolite precursor

Chinese ink-promoted co-assembly synthesis of 3D hierarchically structured and porous MoCx/C nanocomposites for highly efficient hydrogen evolution reaction

Self-supporting composited electrocatalysts of ultrafine Mo2C on 3D-hierarchical porous carbon monoliths for efficient hydrogen evolution

Direct Preparation of High Thermal Stable PLA-Based Nanocomposite via Extra-Low Loading of In Situ Exfoliated Ultrathin MWW Zeolite Nanosheets