Multi-heterointerfaces for selective and efficient urea production

Abstract

A major impediment to the industrial urea synthesis is the lack of catalysts with high selectivity and activity which inhibits the efficient industrial production of urea. Here, we report a new catalyst system suitable for the highly selective synthesis of industrial urea by in-situ growth of graphdiyne on the surface of cobalt-nickel mixed oxides. Such a catalyst is a multi-heterojunction interfacial structure resulting in the obvious incomplete charge transfer phenomenon between graphdiyne and metal oxide interface and multiple intermolecular interactions. These intrinsic characteristics are the origin of the high performance of the catalyst. Studies on mechanism reveal that the catalyst could effectively optimize the adsorption/desorption capacities of the intermediate and promote the direct C-N coupling by significantly suppressing by-product reactions toward the formation of H2, CO, N2, NH3. The catalyst can selectively synthesize urea directly from nitrite and carbon dioxide in water at room temperature and pressure and exhibits record-high Faradaic Efficiency (FE) of 64.3%, nitrogen selectivity (Nurea-selectivity) of 86.0%, carbon selectivity (Curea-selectivity) of ∼100%, as well as the urea yield rates of 913.2 μg h−1 mgcat−1 and remarkable long-term stability.

Synthesis of a Wheel-Shaped Nanographdiyne

“…The ESP on the vdW surface ranges from −22.79 to 19.84 kcal/mol, and the surface area with negative ESP is much larger than that with positive ESP; positive ESP only occurs on the local vdW surface surrounding the outside of peripheral benzene rings. The most negative ESP localizes in the triangle poles, which indicates that the molecular poles of NanoGDY are capable of forming strong electrostatic interaction to cations as supported by the MALDI-TOF signals of 1a binding with one to six cations (Figure S112, further investigation on the cation binding is under way), which means graphdiyne is a versatile substrate for multidimensional catalysts. − Also, alternate distribution of positive and negative ESPs in the peripheral ring was observed; the special stacking behavior of 1c should be the consequence of the ESP complementation principle (Figure a). The butadiyne units promote π–π stacking interactions effectively due to their electron-withdrawing effect …”

Spontaneous hydrogen production using gadolinium telluride

“…Therefore, due to the presence of GdTe in GT-II sample, it regained its ability to produce H 2 when reacted with water at equivalent rate. The minute shift in binding energy indicates the reaction involves a charge transfer, 43 , 44 , 45 although the amount of generated H 2 decreases from freshly prepared GdTe. Furthermore, the de-convoluted XPS profile of tellurium (Te 3d) can be assigned to Te 0 (572.9 eV), O–Te3d 3/2 (575.9 eV), C–Te3d 5/2 (583.3 eV), and O–Te3d 5/2 (586.2 eV) peaks ( Figure 3 H), indicating the formation of elemental Te and oxides of Te along with Gd 2 O 3 and Gd 2 Te 3 .…”

High performance of visible-light driven hydrogen production over graphdiyne (g-CnH2n−2)/MOF S-scheme heterojunction

“…3, there is an obvious incomplete charge transfer between GDY and metal atoms, which plays a very important role in enhancing the overall catalytic performances. [59][60][61][62][63][64] Fig. 3a displays the full spectra of ZnCo-ZIF, GDY and GDY/ZnCo-ZIF-0.9.…”