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To design and build effective electrocatalysts for water splitting is a key challenge, but hardly any non-noble metal catalysts can match the performance of Pt at cathodes and Ir or Ru at anodes. The synergistic combination of non-noble metal catalysts could be a better option for overall water splitting (OWS). Herein, a heterostructured electrocatalyst of MoP/CoMoP2 nanoparticles embedded in an N, P-doped carbon matrix (MoP/CoMoP2@NPC) was fabricated via reticular chemistry. The results indicate that, due to the cooperative effect of MoP/CoMoP2 interfaces and phosphorus vacancies, MoP/CoMoP2@NPC shows extraordinary efficiency and robust stability for hydrogen/oxygen evolution reactions (HER/OER) and OWS in a wide pH range. This work could offer a promising interface-engineering approach to develop and build effective cooperative electrocatalysts for the sustainable production of hydrogen. [ABSTRACT FROM AUTHOR]

Cellulose-based handmade paper records a substantial amount of historical data and promotes human civilization. Due to the complexity of its structure and external factors, the deterioration of paper in the restoration of ancient books cannot be completely stopped. Nonetheless, the lack of microstructure analysis of handmade paper limits the understanding of its aging mechanism and storage life-span. Herein, CP/MAS 13C NMR method was used to estimate the cellulose types, crystallinity, average lateral fibril dimension (LFD), and the average lateral fibril aggregate dimension (LFAD), relying on integrated spectral fitting from C1, C4, and C6 regions, respectively. Consequently, cellulose Iβ crystals were predominant in all handmade paper samples. Based on the results of C4 and C6 regions by peak separation method, bast paper (Kaihua paper and Yingchun paper) demonstrated a higher crystallinity than bamboo paper (Yuanshu paper). Additional analysis of the C4 data revealed that bast papers exhibit larger cellulose microfibrils, and their LFDs and LFADs were greater than bamboo papers. Moreover, external stress of Wiley milling reduced the LFAD from the original 9 elementary fibrils to 4 elementary fibrils with unchanged LFDs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Molybdenum carbides are widely adopted as efficient noble‐metal‐free electrocatalysts for hydrogen evolution reaction (HER). Their surface oxidation is inevitable under air but is often ignored, which can be detrimental for the accurate understanding and precise design of stable carbide catalysts. Herein, molybdenum carbide nanoladders are derived via pyrolyzing MoOx/amine hybrid precursors, and two types of impact of surface oxidation on their HER performance are obvious: (1) the downshift of d‐band center in Mo, and (2) the introduced steric hindrance from surface oxygen. Consequently, the negative hydrogen‐binding free energy (ΔGH*, −0.52 eV) of pristine MoC gradually increases to positive values with surface oxidation, indicating the effectively weakened strength of Mo−H. With moderate surface oxygen incorporation, a ΔGH* of almost 0 eV is in accordance with the efficiently promoted HER performance via a good balance of Volmer and Heyrovsky/Tafel steps in kinetics. The optimal catalyst supported on a Ti plate (1 cm2) gives a high hydrogen production rate of 0.35 mL min−1 at 300 mV with high stability over the self‐made water‐splitting configuration. This work does not only make us reacquaint the surface oxidation of carbides on electrocatalysis but also paves the way for developing efficient and stable catalysts via surface engineering. [ABSTRACT FROM AUTHOR]

Electrocatalytic refinery from biomass-derived glycerol (GLY) to formic acid (FA), one of the most promising candidates for green H 2 carriers, has driven widespread attention for its sustainability. Herein, we fabricated a series of monolithic Ni hydroxide-based electrocatalysts by a facile and in situ electrochemical method through the manipulation of local pH near the electrode. The as-synthesized Ni(OH) 2 @NF-1.0 affords a low working potential of 1.36 V RHE to achieve 100% GLY conversion, 98.5% FA yield, 96.1% faradaic efficiency and ∼0.13 A cm -2 of current density. Its high efficiency on a wide range of polyol substrates further underscores the promise of sustainable electro-refinery. Through a combinatory analysis via H 2 temperature-programmed reduction, cyclic voltammetry and in situ Raman spectroscopy, the precise regulation of synthetic potential was discovered to be highly essential to controlling the content, phase composition and redox properties of Ni hydroxides, which significantly determine the catalytic performance. Additionally, the 'adsorption-activation' mode of ortho -di-hydroxyl groups during the C-C bond cleavage of polyols was proposed based on a series of probe reactions. This work illuminates an advanced path for designing non-noble-metal-based catalysts to facilitate electrochemical biomass valorization., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)