Chang Hyuck Choi

N-doped carbon, a promising alternative to Pt catalyst for oxygen reduction reactions (ORRs) in acidic media, is modified in order to increase its catalytic activity through the additional doping of B and P at the carbon growth step. This additional doping alters the electrical, physical, and morphological properties of the carbon. The B-doping reinforces the sp(2)-structure of graphite and increases the portion of pyridinic-N sites in the carbon lattice, whereas P-doping enhances the charge del

Maximum atom efficiency as well as distinct chemoselectivity is expected for electrocatalysis on atomically dispersed (or single site) metal centres, but its realization remains challenging so far, because carbon, as the most widely used electrocatalyst support, cannot effectively stabilize them. Here we report that a sulfur-doped zeolite-templated carbon, simultaneously exhibiting large sulfur content (17 wt% S), as well as a unique carbon structure (that is, highly curved three-dimensional net

Exposing Fe–N–C catalysts to H ₂ O ₂ -byproduct leaves their catalytic sites untouched but decreases the turnover frequency <italic>via</italic> oxidation of the carbon surface.

Graphene has been highlighted recently as a promising material for energy conversion due to its unique properties deriving from a two-dimensional layered structure of sp2-hybridized carbon. Herein, N-doped graphene (NGr) is developed for its application in oxygen reduction reactions (ORRs) in acidic media, and additional doping of B or P into the NGr is attempted to enhance the ORR performance. The NGr exhibits an onset potential of 0.84 V and a mass activity of 0.45 mA mg−1 at 0.75 V. However,

Fundamental understanding of non-precious metal catalysts for the oxygen reduction reaction (ORR) is the nub for the successful replacement of noble Pt in fuel cells and, therefore, of central importance for a technological breakthrough. Herein, the degradation mechanisms of a model high-performance Fe-N-C catalyst have been studied with online inductively coupled plasma mass spectrometry (ICP-MS) and differential electrochemical mass spectroscopy (DEMS) coupled to a modified scanning flow cell

Continuous on-site electrochemical production of hydrogen peroxide (H2O2) can provide an attractive alternative to the present anthraquinone-based H2O2 production technology. A major challenge in the electrocatalyst design for H2O2 production is that O2 adsorption on the Pt surface thermodynamically favors “side-on” configuration over “end-on” configuration, which leads to a dissociation of O–O bond via dominant 4-electron pathway. This prefers H2O production rather than H2O2 production during t

This review showcases the recent progress in understanding and designing M–N_x/C electrocatalysts towards the ORR, aiming to provide some guidelines for their practical applications in PEMFCs.

N-doped carbon materials are considered as next-generation oxygen reduction reaction (ORR) catalysts for fuel cells due to their prolonged stability and low cost. However, the underlying mechanism of these catalysts has been only insufficiently identified, preventing the rational design of high-performing catalysts. Here, we show that the first electron is transferred into O2 molecules at the outer Helmholtz plane (ET-OHP) over a long range. This is in sharp contrast to the conventional belief t

For a successful replacement of Pt, tremendous efforts have hitherto been made to develop high-performing Fe-N-C catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). In comparison to the remarkable progress in activity, the stability of Fe-N-C catalysts still remains critical, however. Fe demetallation in acidic medium is hypothesized to be one critical factor for the overall lifetime. In contrast to the general belief, we herein demonstrate usin

A new strategy for enhancing the oxygen reduction reaction (ORR) activity of carbon-based catalysts in acidic media is proposed and characterized; the strategy consists in modifying the ORR through dual doping of nitrogen and phosphorus into the carbon. The P, N-doped carbon is prepared via pyrolysis of a mixture composed of dicyandiamide (DCDA), phosphoric acid, cobalt chloride, and iron chloride at 900 °C under an Ar atmosphere. The P-doping induces an uneven surface with many open edged sites

Abstract Fe‐N‐C catalysts with high O 2 reduction performance are crucial for displacing Pt in low‐temperature fuel cells. However, insufficient understanding of which reaction steps are catalyzed by what sites limits their progress. The nature of sites were investigated that are active toward H 2 O 2 reduction, a key intermediate during indirect O 2 reduction and a source of deactivation in fuel cells. Catalysts comprising different relative contents of FeN x C y moieties and Fe particles encap

Heteroatom (nitrogen and sulfur)-doped carbons were synthesized via the pyrolysis of composites composed of iron chloride, cobalt chloride and five different amino acids (alanine, cysteine, glycine, niacine and valine), and their electrocatalytic activity towards oxygen reduction reactions (ORR) compared with each other for fuel cell applications. In all of the prepared catalysts, carbon was doped by nitrogen, and, in particular, a catalyst synthesized from cysteine was dual-doped with nitrogen

Phosphorus and/or sulfur are additionally doped into N-doped carbon (NDC) using phosphoric acid and cysteine. The resulting catalysts demonstrate excellent oxygen reduction activities coupled with high stabilities in acidic media. Specially, additional S-doping in NDC reveals nearly 2.5 times higher activity than that of NDC at 0.75 V (vs. RHE).

Electrocatalytic conversion of CO₂ into value-added products offers a new paradigm for a sustainable carbon economy. For active CO₂ electrolysis, the single-atom Ni catalyst has been proposed as promising from experiments, but an idealized Ni-N₄ site shows an unfavorable energetics from theory, leading to many debates on the chemical nature responsible for high activity. To resolve this conundrum, here we investigated CO₂ electrolysis of Ni sites with

Despite the promising activity of Fe-N-C catalysts at the beginning of life in proton-exchange membrane fuel cells (PEMFCs), their poor durability in operating PEMFCs remains a great challenge for the successful replacement of commercial Pt-based catalysts. One of the key reasons for this poor operando durability is the surface oxidation of carbonaceous supports via Fenton(-like) reactions between the Fe centers and the intermediate product of the oxygen reduction reaction (ORR) in an acidic med