The modulation of the electronic structure is the effective access to achieve highly active electrocatalysts for the hydrogen evolution reaction (HER). Transition-metal phosphide-based heterostructures are very promising in enhancing HER performance but the facile fabrication and an in-depth study of the catalytic mechanisms still remain a challenge. In this work, the catalytically inactive n-type CeO x is successfully combined with p-type CoP to form the CoP/CeO x heterojunction. The crystalline–amorphous CoP/CeO x heterojunction is fabricated by the phosphorization of predesigned Co(OH)2/CeO x via the as-developed reduction–hydrolysis strategy. The p–n CoP/CeO x heterojunction with a strong built-in potential of 1.38 V enables the regulation of the electronic structure of active CoP within the space–charge region to enhance its intrinsic activity and facilitate the electron transfer. The functional CeO x entity and the negatively charged CoP can promote the water dissociation and optimize H adsorption, synergistically boosting the electrocatalytic HER output. As expected, the heterostructured CoP/CeO x -20:1 with the optimal ratio of Co/Ce shows significantly improved HER activity and favorable kinetics (overpotential of 118 mV at a current density of 10 mA cm–2 and Tafel slope of 77.26 mV dec–1). The present study may provide new insight into the integration of crystalline and amorphous entities into the p–n heterojunction as a highly efficient electrocatalyst for energy storage and conversion.
for removing iodine because of their porous structure, such as metal-organic frameworks (MOFs) [4] and porous organic polymers (POPs). [5] Although most of these organic or metallic hybrid materials have good chemical and thermal stability, they will inevitably be partially oxidized or carbonized under long-term high-temperature and oxidizing atmosphere in the process of iodine vapor capture. Comparatively speaking, hyperporous carbons by high-temperature pyrolysis are noted for their high surface areas, large pore volumes, and good chemical and thermal stability, and they may be promising adsorbents for iodine capture. [6] Hyperporous carbons can be prepared from various precursors including porous materials including MOFs and POPs and show good performance in the fields of gas storage, catalysts, and energy storage. [7][8][9] While, many of the porous precursors involved costly starting materials or expensive catalysts or rigorous reaction conditions for their preparation, which limit their large-scale applications. [10][11][12] Among POPs, hypercrosslinked polymers (HCPs) have obvious advantages of low cost and easy scalization. [13] However, such hyperporous carbons with high surface area and excellent chemical and thermal stability from HCPs precursors have not been reported in the field of iodine capture until now. Recently, we synthesized triptycene-based hypercrosslinked porous poly mer sponge (THPS) with superior adsorption capacities for organic solvents and dyes. [14] Herein, we further used THPS as precursor to prepared hyperporous carbon for iodine capture. Interestingly, the obtained hyperporous carbon (THPS-C) processes high surface area and large pore volume, and displays excellent adsorption ability for iodine vapor. Results and DiscussionThe hyperporous carbon THPS-C was prepared by treating THPS (Scheme 1) at 800 °C for 2 h under argon atmosphere using KOH as chemical activating agent in a mass ratio of 1:4 according to literature methods. [6a,8c] Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and highresolution transmission electron microscopy (HR-TEM) were utilized to confirm the structure and morphology of THPS-C. As shown in Figure 1a,b, THPS-C was composed of substantial irregular sphere particles. HR-TEM image revealed abundant micropores in THPS-C networks (Figure S1, Supporting Considering the nuclear fuel reprocessing conditions at 75 °C and the oxidizability of iodine, thermal and chemical stabilities are especially important for porous materials to enrich iodine. However, most organic or metal coordinated porous materials hardly meet this long-term demand. Here, highly porous carbon is prepared from pyrolysis at high temperature using triptycene-based hypercrosslinked polymer as precursor, and possesses high Brunauer-Emmett-Teller (BET) surface area of 3125 m 2 g −1 and pore volume of 1.60 cm 3 g −1 , and exhibits excellent iodine uptake ability of 340 wt% at 75 °C. Moreover, the obtained hyperporous carbon also displays remarkable capture efficiency of...
Exploring high-efficiency and earth-abundant bifunctional electrocatalysts for overall water splitting is of great significance to meet the requirement of the hydrogen economy, but still faces many challenges. In this work, we propose the chemical etching, successive carbonization, and phosphorization treatment strategy of solid ZIF-67 (ZIF = zeolitic imidazole framework), constructing a hybrid nanostructure with CoP nanoparticles embedded in a hollow N-doped carbon nanocage (h-CoP@NC). The elaborate hollow porous structure is conducive to effectively exposing more active sites and shortening mass-transportation pathways. The nitrogen-doped carbon layer would protect the active CoP units from agglomeration and enhance the conductivity. These structural factors synergistically contribute to the enhanced electrocatalytic performance. As a result, the carbonization-temperature-optimized
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