A highly efficient bifunctional oxygen catalyst is required for practical applications of fuel cells and metal-air batteries, as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are their core electrode reactions. Here, the MO-Co@N-doped carbon (NC, M = Zn or Co) is developed as a highly active ORR/OER bifunctional catalyst via pyrolysis of a bimetal metal-organic framework containing Zn and Co, i.e., precursor (CoZn). The vital roles of inactive Zn in developing highly active bifunctional oxygen catalysts are unraveled. When the precursors include Zn, the surface contents of pyridinic N for ORR and the surface contents of Co-N x and Co 3+ /Co 2+ ratios for OER are enhanced, while the high specific surface areas, high porosity, and high electrochemical active surface areas are also achieved. Furthermore, the synergistic effects between Zn-based and Co-based species can promote the well growth of multiwalled carbon nanotubes (MWCNTs) at high pyrolysis temperatures (≥700 °C), which is favorable for charge transfer. The optimized CoZn-NC-700 shows the highly bifunctional ORR/OER activity and the excellent durability during the ORR/OER processes, even better than 20 wt% Pt/C (for ORR) and IrO 2 (for OER). CoZn-NC-700 also exhibits the prominent Znair battery performance and even outperforms the mixture of 20 wt% Pt/C and IrO 2 .

The selective hydrogenation of halogenated nitrobenzene (HNB) has been a great important chemical reaction in the fine chemical productions. In this study, the effect of metal particle size on the selective hydrogenation of HNB over Pd/C catalysts has been extensively investigated through the combination of theoretical (density functional theory calculations, DFT) and experimental methods. DFT calculations showed that the reaction barriers for dechlorination strongly depend on the type of reaction sites (terrace or edge), while the hydrogenation reaction barriers are nearly the same on different sites, which indicates that Pd nanoparticle size significantly affects the catalyst selectivity. Moreover, Pd nanoparticles with different sizes (from 2.1 to 30 nm) supported on activated carbon were synthesized using the methods developed by our group. In a 500 mL reactor, the selectivity is over 99.90% when the Pd nanoparticles are bigger than 25 nm. Finally, the industrial applications of the proposed catalyst were evaluated in several pilot factories. This study provides useful information on controlling the selectivity of other similar reactions catalyzed by noble-metal nanocatalysts.

Solid materials with special atomic and electronic structures are deemed desirable platforms for establishing clear relationships between surface/interface structure characteristics and electrochemical activity. In this work, nickel boride (Ni x B) and nickel boride/graphene (Ni x B/G) are chosen as positive materials of supercapacitors. The Ni x B/G displays higher specific capacitance (1822 F g–1) than that of Ni x B (1334 F g–1) at 1 A g–1, and it still maintains 1179 F g–1 at 20 A g–1, suggesting the high rate performance. The asymmetric supercapacitor device (Ni x B/G//activated carbon) also delivered a very high energy density of 50.4 Wh kg–1, and the excellent electrochemical performance is ascribed to the synergistic effect of Ni x B, Ni­(BO2)2, and graphene that fully enhances the diffusion of OH– and the electron transport. During the cycles, the prepared ultrafine Ni x B nanoparticles will be gradually in situ converted into β-Ni­(OH)2 which has a smaller particle size than that prepared by other methods. This will enhance the utilization of Ni­(OH)2 and decrease the ion diffusion distance. The electron deficient state of B in Ni­(BO2)2 amorphous shell will make it easy to accept extra electrons, enhancing the adsorption of OH– at the shell surface. Moreover, Ni­(BO2)2 makes strong adhesion between Ni x B (or β-Ni­(OH)2) and graphene and protects the core structure in a stable state, extending the cycle life. The above properties of Ni x B/G endow the electrode good capacitive performance.

Dual metal-organic frameworks (MOFs, i.e., MIL-100(Fe) and ZIF-8) are thermally converted into Fe-Fe 3 C-embedded Fe-N-codoped carbon as platinum group metal (PGM)-free oxygen reduction reaction (ORR) electrocatalysts. Pyrolysis enables imidazolate in ZIF-8 rearranged into highly N-doped carbon, while Fe from MIL-100(Fe) into N-ligated atomic sites concurrently with a few Fe-Fe 3 C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half-cells (0.88 V in base and 0.79 V versus RHE in acid in half-wave potential), a proton exchange membrane fuel cell (0.76 W cm −2 in peak power density) and an aprotic Li-O 2 battery (8749 mAh g −1 in discharge capacity), representing a state-of-the-art PGM-free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe-Fe 3 C contribution to the catalyst performance, suggesting Fe 3 C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate-determining step at the nearby Fe-N-C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy-based functional applications.