Cheolwoo Park

All Publications

• Electrolyte-Engineered Photoelectrochemical Ammonia Oxidation Enabling Sustainable Hydrogen Production via Catalyst Regeneration ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Park, C., Kwak, H., Koh, T., Sohn, Y., Park, H., Gu, G., Moon, G., Kim, W. 2025: e22662

  Abstract

  Ammonia oxidation reaction (AOR) offers a promising carbon-free hydrogen production pathway under ambient conditions, yet practical implementation faces critical challenges from catalyst deactivation and competing side reactions in aqueous systems. We present an electrolyte-engineered approach to photoelectrochemical (PEC) AOR that enables both enhanced hydrogen production and reversible catalyst regeneration. By employing a non-aqueous acetonitrile electrolyte at the BiVO4 photoanode, we suppress competing oxygen evolution and NOx poisoning, achieving a 6.9-fold higher hydrogen yield than aqueous systems. Spectroscopic and electrochemical analyses reveal that catalyst deactivation in water is not permanent but dynamically reversible upon re-exposure to nonaqueous environment, emphasizing the solvent-governed interfacial behavior. This electrolyte-engineering approach proves broadly applicable across metal oxide photoanodes (BiVO4, WO3, α-Fe2O3), establishing a universal design principle for PEC AOR systems. Our findings redefine the role of electrolyte composition in governing interfacial pathways and provide a practical framework for developing high-efficiency ammonia-to-hydrogen conversion platforms with enhanced durability and flexibility.

  View details for DOI 10.1002/anie.202522662

  View details for Web of Science ID 001636910300001

  View details for PubMedID 41387981

• Time-Resolved Spectroelectrochemical Observation of Overlayer-Induced Charge Carrier Dynamics in Water Photooxidation ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Park, C., Cho, K., Fujitsuka, M., Majima, T., Bae, S., Ryu, J., Lee, H., Choi, W., Ahn, T., Kim, W. 2025: e202502805

  Abstract

  Surface and interface engineering is essential for constructing efficient and stable photoelectrodes for photoelectrochemical (PEC) solar fuel production. Despite the recent advances in photoelectrode optimization for the practical application, the corresponding interfacial reaction mechanism has not been elucidated owing to a lack of suitable measurements at the semiconductor-electrolyte interface (SEI). Herein, the key factor for an interfacial reaction in a model system (WO3 photoanode coated with amorphous TiO2 overlayers) is elucidated using operando spectroelectrochemistry. The thin TiO2 overlayers are shown to enhance n-type semiconductor characteristics and heal the excessive oxygen vacancies on the WO3 photoanode surface, which suggests reduced bulk and surface charge carrier recombination and 1.5-fold increase in Faradaic efficiency. Operando transient absorption spectroscopy measurements reveal that the overlayers accelerate the transfer of photogenerated electrons from the electrode to the external circuit and increase the population of trapped holes by promoting band bending, which reveals that the kinetic connection between ultrafast phenomena and real water oxidation reaction. Thus, our work elucidates band bending in the space-charge region as a key factor and provides a major strategy for designing surface-modified PEC devices.

  View details for DOI 10.1002/anie.202502805

  View details for Web of Science ID 001552290600001

  View details for PubMedID 40827862

• Cambered Bipyridyl Ligand with Extended Aryl System Enables Electrochemical Reduction of Carbon Dioxide and Bicarbonate by Mn(bpy)(CO)₃Br-type Catalyst Immobilized on Carbon Nanotubes JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Lee, A. J., Deluca, E. E., Kelly, E. B., Taylor, J. M., Weddle, L. R., Chen, H., Park, C., Loeb, C. K., Chan, T., Kubiak, C. P. 2025; 147 (9): 7411-7422

  Abstract

  Heterogeneous materials containing molecular catalytic sites show promise for electrocatalytic reduction of CO2 to energy-enriched carbon products. Interactions between the catalyst and the heterogeneous support increasingly are recognized as important in governing product selectivity and rate. Recent work on Mn(R-bpy)(CO)3Br type catalysts immobilized on multiwalled carbon nanotubes (MWCNT) demonstrated control of electrocatalytic behavior with steric modification of the molecular catalyst. Phenyl groups installed in the 4,4' positions of the bipyridine ligand (ph-bpy) maximized performance through π-π interactions with the MWCNT support. Herein we report the outcome of extending the ligand π system with Mn(nap-bpy)(CO)3Br (nap-bpy = 4,4'-di(naphthalen-1-yl)-2,2'-bipyridine) and Mn(pyr-bpy)(CO)3Br (pyr-bpy = 4,4'-di(pyren-1-yl)-2,2'-bipyridine) immobilized on MWCNT. We demonstrate exceptional electrocatalysis with Mn(nap-bpy)(CO)3Br/MWCNT (FECO > 92%; JCO = 16.5 mA/cm2) and find that this catalyst electrochemically reduces bicarbonate in the absence of deliberately added CO2 at a remarkable overall selectivity of >80% for carbon products (FEHCOO- = 52% and FECO = 29%). We show diminishing returns to simply adding aromatic character to the bipyridyl ligand with Mn(pyr-bpy)(CO)3Br/MWCNT and observe a unique cambering of the Mn(nap-bpy)(CO)3Br bipyridyl ligand that we believe enables selective catalysis. Mechanistic studies were carried out on Mn(nap-bpy)(CO)3Br/MWCNT using a novel thin-film infrared spectroelectrochemical (IR-SEC) technique. These experiments observe the immobilized Mn(nap-bpy)(CO)3Br undergo single electron reduction to a Mn-centered radical that binds CO2 in a reduction-coupled process.

  View details for DOI 10.1021/jacs.4c15547

  View details for Web of Science ID 001433970600001

  View details for PubMedID 39992177

  View details for PubMedCentralID PMC11887433

• Potential of homogeneous persulfate activation as a strategy for the oxidative treatment of tetramethylammonium hydroxide: Superiority of sulfate radical over hydroxyl radical in the oxidation of methylammoniums CHEMICAL ENGINEERING JOURNAL Choi, W., Min, D., Kim, M., Park, C., Choi, Y., Kim, J., Ahn, Y., Yun, E., Lee, Y., Lee, C., Kim, W., Lee, J. 2024; 500

  View details for DOI 10.1016/j.cej.2024.157439

  View details for Web of Science ID 001358436900001

• Selective photocatalytic reduction of nitric oxide to dinitrogen via bimetallic bond incorporation CHEMICAL ENGINEERING JOURNAL Zhang, Z., Park, C., Noh, S., Kim, H., Ahn, T., Kim, W. 2024; 499

  View details for DOI 10.1016/j.cej.2024.156569

  View details for Web of Science ID 001339439500001

• Time-resolved spectroscopic investigation for the practical application of a photocatalytic air purifier JOURNAL OF HAZARDOUS MATERIALS Park, C., Shin, G., Chung, M., Koo, M., Ham, D., Lee, H., Weon, S., Kim, W. 2024; 472: 134382

  Abstract

  The photocatalytic efficiency for removing volatile organic compounds (VOCs) is significantly influenced by operational parameters like humidity and flow velocity, exhibiting notable and inconsistent fluctuations in both lab-scale and large-scale demonstrations. In this study, operando spectroscopy and isotope analysis were employed to investigate the correlation between humidity levels and degradation of gaseous acetaldehyde using TiO2 photocatalysts, aiming to demonstrate the scaling-up of photocatalytic air purifier. It was observed that rate constants for the mineralization of acetaldehyde rapidly decreased by 30% as relative humidity increased from 25% to 80% in the flow system (with an air velocity, v = 0.78 m/s). However, batch system showed smaller change with only a 10% reduction of the rate constant. Humidity fluctuations were more pronounced under high-speed conditions and were amplified in air purifier (v = 3.8 m/s). Time-resolved operando spectroscopy using an 13C isotope of acetaldehyde revealed that humidity's distinct role in dark adsorption and photocatalytic reactions. Water was found to inhibit the formation of crotonaldehyde during aldol condensation reaction in dark condition. Moreover, water suppressed photocatalytic mineralization by inhibiting acetate oxidation to formate. These findings provide valuable insights for improving realistic air purification processes, underscoring the importance of identifying key intermediates and controlling humidity to enhance the selectivity of gaseous pollutant oxidation reactions.

  View details for DOI 10.1016/j.jhazmat.2024.134382

  View details for Web of Science ID 001238089500001

  View details for PubMedID 38703675

• Black phosphorene as a hole extraction layer boosting solar water splitting of oxygen evolution catalysts NATURE COMMUNICATIONS Zhang, K., Jin, B., Park, C., Cho, Y., Song, X., Shi, X., Zhang, S., Kim, W., Zeng, H., Park, J. 2019; 10

  View details for DOI 10.1038/s41467-019-10034-1

  View details for Web of Science ID 000466337500002

• Black phosphorene as a hole extraction layer boosting solar water splitting of oxygen evolution catalysts. Nature communications Zhang, K. n., Jin, B. n., Park, C. n., Cho, Y. n., Song, X. n., Shi, X. n., Zhang, S. n., Kim, W. n., Zeng, H. n., Park, J. H. 2019; 10 (1): 2001

  Abstract

  As the development of oxygen evolution co-catalysts (OECs) is being actively undertaken, the tailored integration of those OECs with photoanodes is expected to be a plausible avenue for achieving highly efficient solar-assisted water splitting. Here, we demonstrate that a black phosphorene (BP) layer, inserted between the OEC and BiVO4 can improve the photoelectrochemical performance of pre-optimized OEC/BiVO4 (OEC: NiOOH, MnOx, and CoOOH) systems by 1.2∼1.6-fold, while the OEC overlayer, in turn, can suppress BP self-oxidation to achieve a high durability. A photocurrent density of 4.48 mA·cm-2 at 1.23 V vs reversible hydrogen electrode (RHE) is achieved by the NiOOH/BP/BiVO4 photoanode. It is found that the intrinsic p-type BP can boost hole extraction from BiVO4 and prolong holes trapping lifetime on BiVO4 surface. This work sheds light on the design of BP-based devices for application in solar to fuel conversion, and also suggests a promising nexus between semiconductor and electrocatalyst.

  View details for PubMedID 31043598