Dual‐Metal Atom Electrocatalysts: Theory, Synthesis, Characterization, and Applications (Adv. Energy Mater. 3/2022)

Experimental and Theoretical Advances on Single Atom and Atomic Cluster‐Decorated Low‐Dimensional Platforms towards Superior Electrocatalysts

“…For example, HAADF‐STEM, EXAFS spectra, and XANES spectra can all be used to entirely understand the physical and chemical features of the as‐synthesized electrocatalysts. [ 106,107 ] Furthermore, density functional theory (DFT) calculations have been very useful to study the electrocatalytic active sites, thus enhancing our knowledge about the electrocatalytic pathways on the surfaces of ACEs. [ 1,108,109 ]…”

“…Figuring out the interaction between the atomic cluster and the substrates could guide the rational design of highly efficient catalysts. [ 109,171,172 ] Carbon‐based LD materials including graphene, [ 173–175 ] graphdiyne (GDY), [ 176–178 ] g‐C 3 N 4 , [ 11,179,180 ] CN [ 181–183 ] and their derivatives have attracted huge interests in designing various electrocatalysts. The electronic properties of atomic clusters could be modified by loading on different substrates.…”

Emerging Graphene Derivatives and Analogues for Efficient Energy Electrocatalysis

“…[ 111,112 ] Recently, the elaborate design of dual‐atom catalysts (DACs) and atomic clusters has gained increasing attention as promising intermediate states bridging SACs and nanoparticles. [ 103,113–116 ] Briefly, the DACs can be divided into three types ( Figure a): [ 103,111 ] 1) mononuclear heterogeneous single atoms (M 1 + M 2 ) with two kinds of atomic metal sites randomly distributed, 2) homonuclear DACs (M 1 –M 1 ) with two same metal atoms adjacent to each other, and; 3) heteronuclear DACs (M 1 –M 2 ) two different metal atoms adjacent to each other. Besides, the orientation of adjacent metal sites can be “in‐plane” or “cofacial.” [ 113,117 ] Compared with SACs, the synergistic incorporation of additional atomic metal sites with metal–metal bonds or a close distance endows great superiority and flexibility in increasing the metal atom loading and regulating the electronic structure of active sites, ultimately achieving enhanced electrocatalytic performance.…”

“…[ 103,113–116 ] Briefly, the DACs can be divided into three types ( Figure a): [ 103,111 ] 1) mononuclear heterogeneous single atoms (M 1 + M 2 ) with two kinds of atomic metal sites randomly distributed, 2) homonuclear DACs (M 1 –M 1 ) with two same metal atoms adjacent to each other, and; 3) heteronuclear DACs (M 1 –M 2 ) two different metal atoms adjacent to each other. Besides, the orientation of adjacent metal sites can be “in‐plane” or “cofacial.” [ 113,117 ] Compared with SACs, the synergistic incorporation of additional atomic metal sites with metal–metal bonds or a close distance endows great superiority and flexibility in increasing the metal atom loading and regulating the electronic structure of active sites, ultimately achieving enhanced electrocatalytic performance. [ 111,115 ] As shown in Figure 4b, the reactant and intermediate molecules can exhibit much more possibilities of adsorption configuration on DACs than that on SACs, [ 111 ] which can provide asymmetric, multiple, and synergistic adsorption sites to break the linear scaling relation among different intermediates.…”

“…The isolated distribution of metal atoms has been solidly confirmed by high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) with electron energy loss spectroscopy (EELS), EXAFS, and X‐ray absorption near‐edge structure (XANES), which are the most powerful and essential tools for identifying the atomic structure and coordination environments of DACs. [ 103,113,128 ] The interaction or electron transfer between nearby metal atoms can be detected by Infrared spectroscopy (CO adsorption), [ 111,129 ] XANES analysis, [ 123,127,130 ] Mössbauer spectroscopy, [ 130 ] and other spectroscopic techniques. However, it is noteworthy that these techniques mostly provide statistical average information, [ 111 ] and cannot unambiguously characterize the specific distribution and configuration among different metal atoms.…”