The rational design of efficient, low cost, and durable catalysts is critical for the industrial applications of electrocatalytic hydrogen production. A key step towards the structure design of high-performance catalysts for hydrogen evolution reaction (HER) relies on the in situ identification of the catalytic active sites in the process of HER, which is of great challenge. In this review, we summarize the recent advances on the in situ investigation of the active sites on low dimensional catalysts for HER. We highlight the characterization techniques used for this purpose, including scanning electrochemical microscopy (SECM), scanning electrochemical cell microscopy (SECCM), electrochemical scanning tunneling microscopy (EC-STM), in situ liquid phase transmission electron microscopy (LP-TEM), and in situ spectroscopic tools. We conclude with an overview of the main technical limitations for the current approaches and give an outlook to future opportunities in this emerging field.

Novel physical properties emerge when the thickness of charge density wave (CDW) materials is reduced to the atomic level, owing to the significant modification of the electronic band structure and correlation effects. Here, we investigate the layer-dependent CDW phase transition and evolution of the nonequilibrium state of 1T-TaS₂ nanoflakes using pump-probe spectroscopy. Both the low-energy single-particle and collective excitation relaxations exhibit sharp changes at ~ 210 K, indicating a phase transition from commensurate CDW to nearly commensurate CDW state. The single particle process reveals that the phase transition stiffness (PTS) is thickness-dependent. Moreover, a small PTS is observed in thin nanoflakes, which is attributed to the reduced thickness that increases the fluctuation and inhibits the nucleation and growth of discommensurations. In addition, the phase mode vanishes when the discommensuration network appears. Our results suggest that the carrier dynamics could be an efficient operational approach to measuring the quantum phase transition in correlated materials.

Two-dimensional ZrS₂ materials have potential for applications in nanoelectronics because of their theoretically predicted high mobility and sheet current density. Herein, we report the thickness and temperature dependent transport properties of ZrS₂ multilayers that were directly deposited on hexagonal boron nitride (h-BN) by chemical vapor deposition. Hysteresis-free gate sweeping, metalinsulator transition, and T^–γ (γ ~ 0.82–1.26) temperature dependent mobility were observed in the ZrS₂ films.

Protein coronas provide the biological identity of nanomaterials in vivo. Here we have used dynamic light scattering (DLS) and transmission electron microscopy (TEM) to investigate the adsorption of serum proteins, including bovine serum albumin (BSA), transferrin (TRF) and fibrinogen (FIB), on gold nanoparticles (AuNPs) with different surface modifications (citrate, thioglycolic acid, cysteine, polyethylene glycol (PEG, M_w = 2 k and 5 k)). AuNPs with PEG(5 k) surface modification showed no protein adsorption. AuNPs with non-PEG surface modifications showed aggregation with FIB. AuNPs with citrate and thioglycolic acid surface modifications showed 6–8 nm thick BSA and TRF coronas (corresponding to monolayer or bilayer proteins), in which the microscopic dissociation constants of BSA and TRF protein coronas are in the range of 10^–8 to 10^–6 M.