The design of active, selective, and stable CO reduction electrocatalysts is still challenging. A series of atomically dispersed Co catalysts with different nitrogen coordination numbers were prepared and their CO electroreduction catalytic performance was explored. The best catalyst, atomically dispersed Co with two-coordinate nitrogen atoms, achieves both high selectivity and superior activity with 94 % CO formation Faradaic efficiency and a current density of 18.1 mA cm at an overpotential of 520 mV. The CO formation turnover frequency reaches a record value of 18 200 h , surpassing most reported metal-based catalysts under comparable conditions. Our experimental and theoretical results demonstrate that lower a coordination number facilitates activation of CO to the CO intermediate and hence enhances CO electroreduction activity.

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The design of active,s elective,a nd stable CO 2 reduction electrocatalysts is still challenging.Aseries of atomically dispersed Co catalysts with different nitrogen coordination numbers were prepared and their CO 2 electroreduction catalytic performance was explored. The best catalyst, atomically dispersed Co with two-coordinate nitrogen atoms,achieves both high selectivity and superior activity with 94 %C Of ormation Faradaic efficiency and ac urrent density of 18.1 mA cm À2 at an overpotential of 520 mV.T he CO formation turnover frequency reaches ar ecordv alue of 18 200 h À1 ,s urpassing most reported metal-based catalysts under comparable conditions.O ur experimental and theoretical results demonstrate that lower ac oordination number facilitates activation of CO 2 to the CO 2 C À intermediate and hence enhances CO 2 electroreduction activity.Considering the increased atmospheric carbon dioxide (CO 2 )c oncentration, electroreduction of CO 2 into valueadded products is ap romising approach to curb anthropogenic CO 2 emissions and alleviate the energy crisis. [1] To gain the practical electrocatalyst enabling low overpotential and high selectivity,s everal metal-based nanostructures such as functionalized metals, [2] metal oxides, [3] and metal disulfides [4] have been developed. However,t he intrinsic mechanism in activation of CO 2 into the CO 2 C À intermediate and how the microstructures compose of metal and native moieties influence the electrocatalytic activity still remain elusive. [1e, 3] Thee merging atomically dispersed metal catalysts,w ith definite structure as active sites,p rovide the possibility to explore the structure-activity relationship. [5] To strengthen the molecular understanding in the reaction intermediates and the reactive sites,w ec reate as eries of atomically dispersed Co catalysts with different Ncoordination numbers and study their catalytic performance towards CO 2 reduction. Themodulation in the surrounding Nnumbers of central Co sites is based on controlling the volatile CÀNf ragments at different pyrolysis temperatures.T he decreased coordinating Nresults in more unoccupied 3d orbitals of Co atoms,which benefits the adsorption of CO 2 C À and increases CO 2 reduction rate.A saresult, the catalyst based on Co-N 2 sites gained higher activity and selectivity than an early inert catalyst mainly comprising Co-N 4 sites,with current densities of about 18.1 mA cm À2 and aC OF aradaic efficiencyo f9 4% at al ow overpotential of 520 mV.M oreover,t he CO formation turnover frequency catalyzed by Co-N 2 sites reached ar ecord value of 18 200 h À1 ,w hich surpasses most of the reported metal-based catalysts under comparable conditions. [2a,6] Since the activity,s electivity,a nd durability of single-site catalysts are highly sensitive to their local coordination environment, [5b, 7] our findings underline the importance of coordination tailoring over reactive sites in triggering the efficient CO 2 electroreduction.Atomically dispersed Co catalysts were firstly prepared by am od...

Noble metal nanomaterials have been widely used as catalysts. Common techniques for the synthesis of noble metal often result in crystalline nanostructures. The synthesis of amorphous noble metal nanostructures remains a substantial challenge. We present a general route for preparing dozens of different amorphous noble metal nanosheets with thickness less than 10 nm by directly annealing the mixture of metal acetylacetonate and alkali salts. Tuning atom arrangement of the noble metals enables to optimize their catalytic properties. Amorphous Ir nanosheets exhibit a superior performance for oxygen evolution reaction under acidic media, achieving 2.5-fold, 17.6-fold improvement in mass activity (at 1.53 V vs. reversible hydrogen electrode) over crystalline Ir nanosheets and commercial IrO2 catalyst, respectively. In situ X-ray absorption fine structure spectra indicate the valance state of Ir increased to less than + 4 during the oxygen evolution reaction process and recover to its initial state after the reaction.

Developing a facile route to access active and well-defined single atom sites catalysts has been a major area of focus for single atoms catalysts (SACs). Herein, we demonstrate a simple approach to generate atomically dispersed platinum via a thermal emitting method using bulk Pt metal as a precursor, significantly simplifying synthesis routes and minimizing synthesis costs. The ammonia produced by pyrolysis of Dicyandiamide can coordinate with platinum atoms by strong coordination effect. Then, the volatile Pt­(NH3) x can be anchored onto the surface of defective graphene. The as-prepared Pt SAs/DG exhibits high activity for the electrochemical hydrogen evolution reaction and selective oxidation of various organosilanes. This viable thermal emitting strategy can also be applied to other single metal atoms, for example, gold and palladium. Our findings provide an enabling and versatile platform for facile accessing SACs toward many industrial important reactions.

Herein, a series of porous nano-structured carbocatalysts have been fused and decorated by Mo-based composites, such as Mo2 C, MoN, and MoP, to form a hybrid structures. Using the open porosity derived from the pyrolysis of metal-organic frameworks (MOFs), the highly dispersive MoO2 small nanoparticles can be deposited in porous carbon by chemical vapor deposition (CVD). Undergoing different treatments of carbonization, nitridation, and phosphorization, the Mo2 C-, MoN-, and MoP-decorated carbocatalysts can be selectively prepared with un-changed morphology. Among these Mo-based composites, the MoP@Porous carbon (MoP@PC) composites exhibited remarkable catalytic activity for the hydrogen evolution reaction (HER) in 0.5 m H2 SO4 aqueous solution versus MoO2 @PC, Mo2 C@PC, and MoN@PC. This study gives a promising family of multifunctional lab-on-a-particle architectures which shed light on energy conversion and fuel-cell catalysis.

Designing highly active catalysts at an atomic scale is required to drive the hydrogen evolution reaction (HER). Copper-platinum (Cu-Pt) dual sites were alloyed with palladium nanorings (Pd NRs) containing 1.5 atom % Pt, using atomically dispersed Cu on ultrathin Pd NRs as seeds. The ultrafine structure of atomically dispersed Cu-Pt dual sites was confirmed with X-ray absorption fine structure (XAFS) measurements. The Pd/Cu-Pt NRs exhibit excellent HER properties in acidic solution with an overpotential of only 22.8 mV at a current density of 10 mA cm and a high mass current density of 3002 A g at a -0.05 V potential.

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