Single‐Atom Catalysts for Electrocatalytic Applications

Abstract

The recent advances in electrocatalysis for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR) are thoroughly reviewed. This comprehensive review focuses on the single‐atom catalysts (SACs) including Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Sn, W, Bi, Ru, Rh, Pd, Ag, Ir, Pt, and Au with single‐metal sites or dual‐metal sites. The recent development of single‐atom electrocatalysts with novel configurations and compositions is documented. The understanding of the process–structure–property relationships is highlighted. For the SACs, their electrocatalytic performance and stability in fuel cells, zinc–air batteries, electrolyzers, CO2RR, and NRR are summarized. The challenges and perspectives in the emerging field of single‐atom electrocatalysis are discussed.

Cobalt/nitrogen codoped carbon nanosheets derived from catkins as a high performance non-noble metal electrocatalyst for oxygen reduction reaction and hydrogen evolution reaction

“…S3b †). 2,16 The acid leaching followed by the second pyrolysis nearly leads to the absence of the crystalline cobalt phase, as demonstrated by the trace (111) reections of the XRD pattern in Fig. S3c.…”

“…1c) with an interlayer spacing of about 0.348 nm, corresponding to that of the (002) plane of graphitic carbon. 2,10 One should bear in mind that only the diffracted rings are seen in the SADE pattern (inset of Fig. 1c), suggesting the removal of most cobalt nanoparticles by the acid leaching.…”

“…† Furthermore, we employed X-ray photoelectron spectroscopy (XPS) to identify the elements and their surface chemical states of the as-prepared electrocatalysts. 1,2,15 Fig. 2a displays the XPS survey spectrum of the sample pyrolyzed at 800 C, which conrms the existence of C, N, O, and Co, and the elemental contents of N and Co are also listed in Fig.…”

“…Besides these peaks, an extra strong Co-N peak was observed at 781.1 eV. 2,19,38 Aer the acid leaching and second pyrolysis, no metallic Co and Co 2+ peaks were observed, suggesting that the remaining Co species are coordinated with N in Co-N x moieties in the carbon matrix. 1,32 Such Co-N x coordination, which would generate a strong electronwithdrawing effect, could cause an electron density migration of adjacent C atoms.…”

“…Developing novel energy conversion and storage systems such as overall water splitting, metal-air batteries and proton exchange membrane fuel cells (PEMFCs) may be taken as a relatively ideal and sustainable alternative for easing the energy and environmental crisis arising from traditional fossil fuels. [1][2][3][4] Among the energy devices mentioned above, PEMFCs were commercialized in automobiles in 2014 and thus considered as one of the most efficient power sources for automotives. 5 Such energy conversion systems mainly consist of four core electrocatalytic processes, which are the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER).…”