Vacancy engineering is an effective strategy to manipulate the electronic structure of electrocatalysts to improve their performance, but few reports focus on phosphorus vacancies (Pv). Herein, the creation of Pv in metal phosphides and investigation of their role in alkaline electrocatalytic hydrogen evolution reaction (HER) is presented. The Pv‐modified catalyst requires a minimum onset potential of 0 mV vs. RHE, a small overpotential of 27.7 mV to achieve 10 mA cm−2 geometric current density and a Tafel slope of 30.88 mV dec−1, even outperforms the Pt/C benchmark (32.7 mV@10 mA cm−2 and 30.90 mV dec−1). This catalyst also displays superior stability up to 504 hours without any decay. Experimental analysis and density functional theory calculations suggest Pv can weaken the hybridization of Ni 3d and P 2p orbitals, enrich the electron density of Ni and P atoms nearby Pv, and facilitate H* desorption process, contributing to outstanding HER activity and facile kinetics.

Applications for metal-organic frameworks (MOFs) demand their assembly into threedimensional (3D) macroscopic architectures. The capability of sustaining structural integrity with considerable deformation is important to allow a monolithic material to work reliably. Nevertheless, it remains a significant challenge to introduce superplasticity in 3D MOF networks. Here, we report a general procedure for synthesizing 3D superplastic MOF aerogels inspired by the hierarchical architecture of natural corks. The resultant MOFs exhibited excellent superplasticity that can recover fully and rapidly to its original dimension after 50% strain compression and unloading for >2000 cycles. The 3D superplastic architecture is achieved by successively assembling onedimensional (1D) to two-dimensional (2D) and then 3D, in a variety of MOFs with different transition metal active sites (Co-, NiMn-, NiCo-, NiCoMn-) and organic ligands (2-thiophenecarboxylic acid and glutaric acid). Latent applications have been demonstrated for NiMn-MOF aerogels to serve as a new generation of flexible electrocatalysts for hydrogen evolution reaction (HER) from seawater splitting, which requires a low overpotential of 243 mV to achieve a current density of 10 mA⋅cm −2 . Notably, the electrocatalyst remains stable even being deformed, as the overpotential to achieve a current density of 10 mA⋅cm −2 increases slightly to 270, 264, and 258 mV after one-, two-, and threefold, respectively. In great contrast, traditional MOF powder-electrodes demonstrate significant activity decay under similar conditions. This work opens up enormous opportunities for exploring new applications of MOFs in a freestanding, structurally adaptive, and macroscopic form.

We demonstrate good agreement between the theoretical and experimental collision frequency of individual Pt nanoparticles (NPs) undergoing collisions at a Au ultramicroelectrode (UME) (5 μm radius) using electrocatalytic amplification provided by 15 mM hydrazine in 5 mM phosphate buffer (PB; pH 7) over 100 to 300 s. Dynamic light scattering (DLS) measurements demonstrated that Pt NP aggregation in this solution had the least impact on NP diffusion coefficient and concentration values, which are directly proportional to collision frequency. We show that the smaller, uniform current steps are indicative of NPs of metallic radii in agreement with those determined by transmission electron microscopy (TEM), with corresponding larger NP diffusion coefficient and concentration, in agreement with DLS results. These contribute to the larger NP collision frequency observed experimentally. Using atomic force microscopy (AFM) imaging, we show good agreement between the number of NPs imaged on the UME surface and the number of NP collisions that led to their adsorption, a spherical NP shape with a metallic radius size distribution comparable to that determined by TEM, and a random NP distribution on the UME surface. Through the Pt NP electroactive surface area, we show that all NPs on the UME surface after collision are attached and electrochemically active. Collectively, these results demonstrate for the first time that, within experimental error, every NP collision is successful and occurs through a sticking mechanism. Thus, collision experiments can be used to prepare small NP ensembles on a UME (i.e., UME-NPEs). In electrocatalysis, such UME-NPEs bridge the gap between classical ensemble studies on large platforms and isolated single NP investigations.

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Super absorbent polymers of acrylic acid-graphene oxide (PAA-GO) were synthesized with different percentage of chemical neutralization (0, 10, and 20%) of the acrylic acid monomer before its polymerization. The influence of their swelling and adsorption/desorption capacity of cadmium ions in aqueous solutions were studied and revealed that the GO enables greater mechanical stability in the materials. The PAA hydrogels, with the same degrees of neutralization, were also prepared without GO to compare with the composites. Additionally, carbon paste electrodes (CPE) modified with the composites PAA-GO were used to asses and compare their adsorption properties with cadmium(II). The anodic stripping voltammetry (ASV) peak, in the differential pulse voltammetry mode, for cadmium oxidation was found to be influenced by the presence of GO into the polymer, and also by their percentage of neutralization. The accumulation of cadmium(II) on the surface of the modified CPEs was performed under opencircuit conditions taking an account the preconcentration time of the metal cation. The presence of GO enhances the electrical signal of the electrodes in short times of immersion in cadmium(II) solutions. This property contributed to get linear responses of the CPEs modified with the composites, which were influenced by their degrees of neutralization. The PAA-GO 10N electrode with 10% of neutralization combined the influence of GO and the degree of neutralization in the same matrix, and also showed good performance in terms of its mechanical stability, it was chosen for preliminary studies on the selectivity of the electrode toward Zn(II) and Cu(II).