https://scholar.dgist.ac.kr/handle/20.500.11750/11833 2026-04-06T13:09:45Z https://scholar.dgist.ac.kr/handle/20.500.11750/47733 Title: Trace-Level Cobalt Dopants Enhance CO2 Electroreduction and Ethylene Formation on Copper Author(s): Kim, Beomil; Tan, Ying Chuan; Ryu, Yeonkyeong; Jang, Kyuseon; Abbas, Hafiz Ghulam; Kang, Taehyeok; Choi, Hyeonuk; Lee, Kug-Seung; Park, Sojung; Kim, Wooyul; Choi, Pyuck-Pa; Ringe, Stefan; Oh, Jihun Abstract: The development of Cu-based catalysts for electrochemical CO2 reduction reaction (CO2RR) with stronger CO-binding elements had been unsuccessful in improving multicarbon production from the CO2RR due to CO-poisoning. Here, we discover that trace doping levels of Co atoms in Cu, termed CoCu single-atom alloy (SAA), achieve up to twice the formation rate of CO as compared to bare Cu and further demonstrate a high jC of 282 mA cm-2 at −1.01 VRHE in a neutral electrolyte. From DFT calculations, Cu sites neighboring CO-poisoned Co atomic sites accelerate CO2-to-CO conversion and enhance the coverage of *CO intermediates required for the formation of multicarbon products. Furthermore, CoCu SAA also exhibits active sites that favor the deoxygenation of *HOCCH, which increases the selectivity toward ethylene over ethanol. Ultimately, CoCu SAA can simultaneously boost the formation of *CO intermediates and modulate the selectivity toward ethylene, resulting in one of the highest ethylene yields of 15.6%. © 2023 American Chemical Society. 2023-06-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/46082 Title: Active and stable PtP2-based electrocatalysts solve the phosphate poisoning issue of high temperature fuel cells Author(s): Yu, Jeong-Hoon; Singh, Kiran Pal; Kim, Se-Jun; Kang, Tong-Hyun; Lee, Kug-Seung; Kim, Hyungjun; Ringe, Stefan; Yu, Jong-Sung Abstract: Platinum (Pt) loaded over a carbon support is known to be the best and most effective electrocatalyst for the oxygen reduction reaction (ORR). However, given its high surface energy, it tends to lose its catalytic activity after an unacceptably short period of usage. The stability of Pt has always been a bottleneck in commercializing the polymer electrolyte membrane fuel cell (PEMFC). In high temperature-polymer electrolyte membrane fuel cells (HT-PEMFCs), the activity loss has been traced back to the chemisorption of phosphate anions, which irreversibly poison Pt active sites. Herein, we present an alternative Pt phosphide-based (PtP2/C) electrocatalyst for application under high temperature conditions. The prepared PtP2/C catalyst shows surprisingly excellent long-term stability and high catalytic activity in phosphoric acid. From density functional theory (DFT) calculations, we found this to be related to the oxyphilicity of the P atoms which under reaction conditions form a protective phosphorus oxide film that also binds phosphoric acid more strongly than Pt sites. Thus-protected Pt sites, in particular those from P defects, are predicted to be highly active for the ORR. The improved stability is also the result of a better oxidation resistance of the carbon support in the presence of PtP2 © 2023 The Royal Society of Chemistry. 2023-02-28T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/16957 Title: Using pH Dependence to Understand Mechanisms in Electrochemical CO Reduction br Author(s): Kastlunger, Georg; Wang, Lei; Govindarajan, Nitish; Heenen, Hendrik H.; Ringe, Stefan; Jaramillo, Thomas; Hahn, Christopher; Chan, Karen Abstract: Electrochemical conversion of CO(2)into hydro-carbons and oxygenates is envisioned as a promising path towardclosing the carbon cycle in modern technology. To date, however,the reaction mechanisms toward the plethora of products aredisputed, complicating the search for alternative catalyst materials.To conclusively identify the rate-limiting steps in CO reduction onCu, we analyzed the mechanisms on the basis of constant-potentialdensity functional theory (DFT) kinetics and experiments at a widerange of pH values (3-13). Wefind that*CO dimerization isenergetically favored as the rate-limiting step toward multicarbonproducts. Thisfinding is consistent with our experiments, wherethe reaction rate is nearly unchanged on a standard hydrogenelectrode (SHE) potential scale, even under acidic conditions. Formethane, both theory and experiments indicate a change in the rate-limiting step with electrolyte pH from thefirst protonation stepunder acidic/neutral conditions to a later one under alkaline conditions. We also show, through a detailed analysis of themicrokinetics, that a surface combination of*CO and*H is inconsistent with the measured current densities and Tafel slopes.Finally, we discuss the implications of our understanding for future mechanistic studies and catalyst design. 2022-03-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/16850 Title: Strained Pt(221) Facet in a PtCo@Pt-Rich Catalyst Boosts Oxygen Reduction and Hydrogen Evolution Activity Author(s): Tetteh, Emmanuel Batsa; Gyan-Barimah, Caleb; Lee, Ha-Young; Kang, Tong-Hyun; Kang, Seonghyeon; Ringe, Stefan; Yu, Jong-Sung Abstract: Over the last years, the development of highly active and durable Pt-based electrocatalysts has been identified as the main target for a large-scale industrial application of fuel cells. In this work, we make a significant step ahead in this direction by preparing a high-performance electrocatalyst and suggesting new structure-activity design concepts which could shape the future of oxygen reduction reaction (ORR) catalyst design. For this, we present a new one-dimensional nanowire catalyst consisting of a L1(0) ordered intermetallic PtCo alloy core and compressively strained high-index facets in the Pt-rich shell. We find the nanoscale PtCo catalyst to provide an excellent turnover for the ORR and hydrogen evolution reaction (HER), which we explain from high-resolution transmission electron microscopy and density functional theory calculations to be due to the high ratio of Pt(221) facets. These facets include highly active ORR and HER sites surprisingly on the terraces which are activated by a combination of sub-surface Co-induced high Miller index-related strain and oxygen coverage on the step sites. The low dimensionality of the catalyst provides a cost-efficient use of Pt. In addition, the high catalytic activity and durability are found during both half-cell and proton exchange membrane fuel cell (PEMFC) operations for both ORR and HER. We believe the revealed design concepts for generating active sites on the Pt-based catalyst can open up a new pathway toward the development of high-performance cathode catalysts for PEMFCs and other catalytic systems. © 2022 American Chemical Society. All rights reserved. 2022-05-31T15:00:00Z