[en] Highlights: • The excellent HER catalytic activity could be compared with that of commercial Pt/C catalyst. • PVP modified Pt nanoparticles was used to avoid the formation of large Pt aggregate. • Interlayer-expended MoS₂ and highly dispersed Pt nanoparticles are favorable to HER activity. -- Abstract: Ultrafine Pt-decorated interlayer-expanded MoS₂/N-doped carbon composite with sponge-like morphology (Pt–MoS₂/CN) has been synthesized through a one-pot pyrolysis protocol. Using PVP modified Pt colloidal as precursor not only avoids the formation of large Pt particles, but also plays an important role in the formation of highly dispersed interlayer-expanded MoS₂ nanocrystalline within N-doped carbon network. The synergy between Pt nanoparticle and interlayer-expended MoS₂ nanocrystalline gives rise to favorable intrinsic catalytic activity. The resulting Pt-MoS₂/CN composite boosts the hydrogen evolution reaction (HER) performance to an upper level in acidic media with low overpotential (−20 mV at 10 mA cm⁻²), high exchange current density (6.24 mA cm⁻²) and much stable durability (more than 80 h). All these properties can be compared with that of commercial Pt/C catalyst. The excellent electrocatalytic performance, simple preparation and low cost make it a promising candidate for HER.

[en] Highlights: • Al doped CoP₂/rGO composite was prepared using CoAl-LDH as a precursor. • The excellent HER catalytic activity could be compared with that of commercial Pt/C catalyst. • Doping of Al within CoP₂ structure could efficiently promote the catalytic activity for HER. A series of Al-doped CoP₂/rGO composites have been fabricated by in-situ precipitation and phosphorization protocol. The well-ordered arrangement and widely adjustable mole ratio of cations within Co–Al layered double hydroxide (CoAl-LDH) make it suitable as a precursor for phosphiding and generating evenly dispersed Al element within CoP₂ structure. The effect of Al doping content on the catalytic activities for hydrogen evolution reaction thus could be discussed in detail. Electrocatalytic performance indicates that the doping of Al element within CoP₂ structure could efficiently prevent the oxidation of phosphide on the surface, and thus resulting in the high electrocatalytic activity for hydrogen evolution reaction (HER). Among all the Al-doped CoP₂/rGO materials, the composite with the Co/Al mole ratio of 2/1 presents the highest HER activity and stability whatever under acidic or basic reaction conditions, which could be comparable to the most reported HER electrocatalysts and even the commercial 20% Pt/C. At the current density of −10​mA​cm⁻² in 0.5​M​H₂SO₄, the overpotential is only 59​mV with a Tafel slope of 73.2​mV dec⁻¹. Interestingly, the Al content could be dissolved under basic media and resulting in a porous structured electrode. Only the overpotential of 60​mV is needed to get the current density of −10​mA​cm⁻² in 1​M KOH.

[en] Due to heavy metals’ magnified pollution from their accumulation in the ecosystem, practical detection of ultra-low concentration of heavy metals in environmental sample is of great significance for environmental supervision and maintenance of people’s health. Herein, a practical and sensitive assay of heavy metal mercury was developed by visually observing (or spectrum detecting) the change of cationic gold nanoparticles (AuNPs), which is directly caused by mercury ion induced hybridization between non-canonical base pairs. In this assay, signal probe’s response was direct rather than the indirect salt induction, thus avoiding the defect of salt-induced indirect response. It makes the analysis more sensitive. The results showed that the response of 8.2 × 10${}^{-<!--\; ???\; -->8}$ M Hg${}^{2+}$ could be observed with naked eye and the detection limit of Hg${}^{2+}$ in spectrometric determination was 4.9 × 10${}^{-<!--\; ???\; -->11}$ M, which is more than one order of magnitude lower than that from indirect response pattern of signal probe. In addition, high specificity of the affinity chemistry for T–Hg–T renders the assay to be highly selective. Compared with the results of cold vapor atom adsorption spectroscopy (CVAAS), this analysis has good reliability for the detection of mercury. The results fully indicate that the developed assay is an ideal alternative for online detection of heavy metal mercury in environmental pollution samples.