Nickel-nitrogen-modified graphene (Ni-N-Gr) is fabricated and Ni-N coordination sites on Ni-N-Gr as active centers effectively reduce CO to CO. The faradaic efficiency for CO formation reaches 90% at -0.7 to -0.9 V versus RHE, and the turnover frequency for CO production comes up to ≈2700 h at -0.7 V versus RHE.

The electrochemical oxygen reduction reaction (ORR) is an important cathode reaction of various types of fuel cells. The development of electrocatalysts composed only of abundant elements is a key goal because currently only platinum is a suitable catalyst for ORR. Herein, we synthesized copper-modified covalent triazine frameworks (CTF) hybridized with carbon nanoparticles (Cu-CTF/CPs) as efficient electrocatalysts for the ORR in neutral solutions. The ORR onset potential of the synthesized Cu-CTF/CP was 810 mV versus the reversible hydrogen electrode (RHE; pH 7), the highest reported value at neutral pH for synthetic Cu-based electrocatalysts. Cu-CTF/CP also displayed higher stability than a Cu-based molecular complex at neutral pH during the ORR, a property that was likely as a result of the covalently cross-linked structure of CTF. This work may provide a new platform for the synthesis of durable non-noble-metal electrocatalysts for various target reactions.

Nickel-modified covalent triazine frameworks effectively reduced CO2 to CO because adsorbed COOH was stabilized on the coordinatively-unsaturated Ni atoms in CTF.

It was found that copper-modified covalent triazine frameworks (Cu-CTF) efficiently catalyze the electrochemical reduction of nitrate and promote N−N bond formation of nitrous oxide (N 2 O), a key intermediate for N 2 formation (denitrification). A Cu-CTF electrode exhibited an onset potential of −50 mV versus RHE for the electrochemical nitrate reduction reaction (NRR). The faradaic efficiency for N 2 O formation by Cu-CTF reached 18% at −200 mV versus RHE, whereas that for Cu metal was negligible. On the basis of density functional calculations for Cu-CTF, both solvated and surface-bound nitric oxide (NO) were generated by the NRR due to the moderate adsorption strength of Cu atoms for NO, a property that facilitated the effective dimerization of NO through an Eley−Rideal-type mechanism.

So-called local cells resulting from the coupling of oxidation and reduction reactions on the same conductive substrate represent a well-known cause of metallic corrosion. In the present study, we attempted to demonstrate that catalytic systems based on the principle of local cell reactions can be successfully fabricated using metal-doped covalent triazine frameworks as catalytic units. A conductive substrate carrying platinum- and copper-doped covalent triazine frameworks as catalysts for the oxidation and reduction processes, respectively, was developed to fabricate a local cell catalytic unit for the concurrent reduction of nitrate to nitrous oxide and oxidation of hydrogen.