Han et al. have prepared a type of organic-inorganic hybrid material by templatedirected polymerization of cobalt phthalocyanine on carbon nanotubes for a selective CO 2 reduction reaction to CO with a large faradic efficiency, exceptional turnover frequency, and excellent long-term durability.

Electrochemical reduction of CO 2 provides an opportunity to reach a carbon-neutral energy recycling regime, in which CO 2 emissions from fuel use are collected and converted back to fuels. The reduction of CO 2 to CO is the first step towards the synthesis of more complex carbon-based fuels and chemicals. Therefore, understanding this step is crucial for the development of high-performance electrocatalyst for CO 2 conversion to higher order products such as hydrocarbons. Here we synthesize atomic iron dispersed on nitrogen-doped graphene (Fe/NG) as an efficient electrocatalyst for CO 2 reduction to CO. Fe/NG has a low reduction overpotential with high Faradic efficiency up to 80%. The existence of nitrogenconfined atomic Fe moieties on the nitrogen-doped graphene layer was confirmed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure analysis. The Fe/NG catalysts provide an ideal platform for comparative studies of the effect of the catalytic center on the electrocatalytic performance. The CO 2 reduction reaction mechanism on atomic Fe surrounded by four N atoms (Fe-N 4) embedded in nitrogen-doped graphene is further investigated through density functional theory calculations, revealing a possible promotional effect of nitrogen doping on graphene.

The development of nonprecious metal based electrocatalysts for hydrogen evolution reaction (HER) has received increasing attention over recent years. Previous studies have established MoC as a promising candidate. Nevertheless, its preparation requires high reaction temperature, which more than often causes particle sintering and results in low surface areas. In this study, we show supporting MoC nanoparticles on the three-dimensional scaffold as a possible solution to this challenge and develop a facile two-step preparation method for ∼3 nm MoC nanoparticles uniformly dispersed on carbon microflowers (MoC/NCF) via the self-polymerization of dopamine. The resulting hybrid material possesses large surface areas and a fully open and accessible structure with hierarchical order at different levels. MoO was found to play an important role in inducing the formation of this morphology presumably via its strong chelating interaction with the catechol groups of dopamine. Our electrochemical evaluation demonstrates that MoC/NCF exhibits excellent HER electrocatalytic performance with low onset overpotentials, small Tafel slopes, and excellent cycling stability in both acidic and alkaline solutions.

improve the hydrogen evolution reaction (HER) rate. [9][10][11] However, even with this approach, the quantum efficiency (QE) and, subsequently, the solar energy conversion efficiency for a single component material are still relatively low due to the fast recombination of photogenerated electron-hole pairs. [12][13][14][15] Reducing the dimensions of the photocatalyst can improve the photocatalytic activity due to the shortened diffusion length of photogenerated carriers. [16][17][18][19] In this context, graphitic carbon nitride (g-C 3 N 4 ) with atomic thickness has been recently investigated as a promising material for photocatalysis, since it can efficiently separate the photoexcited carriers, which then migrate to the surface with decreased possibility of recombination. [20][21][22] Nevertheless, the synthesis of ultrathin 2D g-C 3 N 4 nanosheets (monolayer or bilayer) with high crystallinity and uniform thickness on a large-scale remains a challenge. To further improve the quantum efficiency of HER, a second semiconductor with band positions complementary to that of g-C 3 N 4 can be introduced, creating an artificial Z-scheme junction, [23,24] able to suppress the recombination of electron-hole pairs and also enhance the light absorption. [25][26][27] By choosing an auxiliary semiconductor with deep valence band (VB), the Z-scheme structure formed with g-C 3 N 4 can also potentially drive the overall water splitting.Here, we, for the first, time developed a catalytic synthesis approach by employing a small amount of metal oxide (e.g., α-Fe 2 O 3 ) as a catalyst to produce ultrathin 2D g-C 3 N 4 nanosheets (one to two layers) on a large scale with a yield of 10 wt%. Meanwhile, the all-solid-state Z-scheme structure forms composed two photocatalysts (n-type α-Fe 2 O 3 nanosheet and n-type 2D g-C 3 N 4 ) in direct and tight contact, which mitigates the competing shuttle-mediator redox reactions and has a simple composition that is more attractive to the research community and industry. [28,29] For hydrogen evolution, the α-Fe 2 O 3 nanosheet/2D g-C 3 N 4 Z-scheme system exhibits a significantly enhanced quantum efficiency up to 44.35% (λ = 420 nm), which is the highest quantum efficiency so far reported for g-C 3 N 4based photocatalysts (see Table S1, Supporting Information). In addition, the quantum efficiency is also superior to most of the semiconductor photocatalysts containing metal oxides and Photocatalysis is the most promising method for achieving artificial photosynthesis, but a bottleneck is encountered in finding materials that could efficiently promote the water splitting reaction. The nontoxicity, low cost, and versatility of photocatalysts make them especially attractive for this application. This study demonstrates that small amounts of α-Fe 2 O 3 nanosheets can actively promote exfoliation of g-C 3 N 4 , producing 2D hybrid that exhibits tight interfaces and an all-solid-state Z-scheme junction. These nanostructured hybrids present a high H 2 evolution rate >3 × 10 4 µmol g -1 h -1 and externa...

Electronic regulation of Mo2C and thus intrinsically improved HER activity via balanced Volmer and Heyrovsky/Tafel steps.