Tailoring the selectivity and activity of oxygen reduction by regulating the coordination environments of carbon-supported atomically dispersed metal sites

Abstract

Oxygen reduction reaction (ORR) is an important half reaction in fuel cells and metal–air batteries as well as in cost-effective electrosynthesis of H2O2. However, the issues of low selectivity and...

Molecular design and coordination regulation of atomically dispersed bi-functional catalysts for oxygen electrocatalysis

“…111 For the regulation of ORR pathway selectivity, the balance between O* and OOH* binding free energies on the reaction site should be considered. 112 In detail, adjusting the chemical environment of the metal central atom to reduce the adsorption energy of O* intermediates while increasing the binding free energy of OOH* is beneficial to the 2e − ORR, and vice versa to the 4e − ORR. For the OER, the presence of the coordinating atom N also brought about a positive effect.…”

Challenges and Perspectives of Single-Atom-Based Catalysts for Electrochemical Reactions

“… 24 − 26 The electronic structure of the metal site can be tuned by the number and kind of first-shell or second-shell atoms, such as N, P, S, and O. 27 − 29 The neighboring metal atom or nanoparticle could also affect the electronic structure of the center metal site. 30 − 32 …”

“…A metal single atom and nonmetallic ligands constitute a metal single-atom site. The nonmetallic ligands not only stabilize the metal single atom but also tune the electronic structure of the metal site, determining the activity, selectivity, and stability of catalysts. − Carbon materials exhibit good stability, high surface area, excellent electrical conductivity, and flexibility with dopants, which make them a popular substrate for electrocatalysts. − As the single metal site is usually stabilized by the nitrogen atoms that are doped in the carbon substrate, carbon-based SACs can be labeled as metal–nitrogen–carbon (M–N–C) catalysts. − The electronic structure of the metal site can be tuned by the number and kind of first-shell or second-shell atoms, such as N, P, S, and O. − The neighboring metal atom or nanoparticle could also affect the electronic structure of the center metal site. − …”

Selective Oxidation of CH4 to CH3OH by Transition-Metal Single-Atom-Embedded N-Doped Graphene Catalysts with Oxidants N2O and O2: Oxygen Adsorption Energy as an Activity Descriptor

“…In the past decade, the development of atomically dispersed TM–N coordination catalysts has received increasing attention in industry and academia. − The TM–N coordination structural unit mimics the metalloporphyrin counterpart of chemical and biological systems, and such a catalytic active site is assembled on different substrate materials to form a large class of novel heterogeneous catalysts. Graphene and analogous carbonaceous backbones are reliable candidates as substrates for TM–N doping, − and transition-metal supported on nitrogen-doped carbon (TM–N/C) materials have been widely used in thermochemical, − electrochemical, − and photochemical − reactions, which generally exhibit promising catalytic performance in a variety of chemical reactions. For instance, the reported high-performance FeN 4 /C catalyst can be used to directly convert CH 4 to CH 3 OH and other C1 oxygenated products at room temperature (25 °C) .…”