Switching Electrocatalytic Hydrogen Evolution Pathways through Electronic Tuning of Copper Porphyrins

Angewandte Chemie International Edition, Год журнала: 2024, Номер 63(13)

Опубликована: Фев. 7, 2024

The electronic structure of metal complexes plays key roles in determining their catalytic features. However, controlling structures to regulate reaction mechanisms is fundamental interest but has been rarely presented. Herein, we report tuning Cu porphyrins switch pathways the hydrogen evolution (HER). Through controllable and regioselective β-oxidation porphyrin 1, synthesized analogues 2-4 with one or two β-lactone groups either a cis trans configuration. Complexes 1-4 have same Cu-N

Язык: Английский

---

Mechanism-Guided Kinetic Analysis of Electrocatalytic Proton Reduction Mediated by a Cobalt Catalyst Bearing a Pendant Basic Site

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(6), С. 3742 - 3754

Опубликована: Фев. 5, 2024

Cobalt polypyridyl complexes stand out as efficient catalysts for electrochemical proton reduction, but investigations into their operating mechanisms, with broad-reaching implications in catalyst design, have been limited. Herein, we investigate the catalytic activity of a cobalt(II) complex bearing pendant pyridyl base series organic acids spanning 20 pKa units acetonitrile. Structural analysis, well studies, reveals that Co(III) hydride intermediate is formed through reduction Co(II) followed by direct metal protonation initial EC step despite presence base, which commonly thought more kinetically accessible site. Protonation occurs after further reduced overall ECEC pathway. Additionally, when acid used sufficiently strong, can be protonated, and react directly to release H2. With thorough mechanistic understanding, appropriate electroanalytical methods were identified extract rate constants elementary steps over range conditions. Thermodynamic square schemes relating intermediates proposed three electrocatalytic HER mechanisms constructed. These findings reveal full description electrocatalysis mediated this molecular system provide insights strategies improve synthetic fuel-forming operative intermediates.

Язык: Английский

---

Deciphering Reaction Mechanisms of Molecular Proton Reduction Catalysts with Cyclic Voltammetry: Kinetic vs Thermodynamic Control

Accounts of Chemical Research, Год журнала: 2025, Номер unknown

Опубликована: Март 4, 2025

ConspectusThe kinetics and thermodynamics of elementary reaction steps involved in the catalytic reduction protons to hydrogen define landscape for catalysis. The mechanisms can differ order proton transfer, electron bond-forming be further differentiated by sites at which electrons localize. Access fully elucidated mechanistic, kinetic, thermochemical details molecular catalysts is crucial facilitate development new that operate with optimal efficiency, selectivity, durability. mechanism a catalyst operates, as well associated individual steps, often accessed through electroanalytical studies.This Account application cyclic voltammetry interrogate quantify series mediate electrochemical reduction. I distinguish limiting scenarios wherein operates under kinetic control vs thermodynamic control, focus on detecting how features shift source strength concentration, scan rate. For systems currents are observed at, or slightly positive toward, formal potential redox process triggers Under responses function pKa effective pH solution. After drawing this distinction, we introduce appropriate experiments accompanying analytical expressions extracting key metrics from data.To illustrate strategies operating describe our studies Co(dmgBF2)2(CH3CN)2 (dmgBF2 = difluoroboryl-dimethylglyoxime) [Ni(P2PhN2Ph)2]2+ (P2PhN2Ph 1,5-phenyl-3,7-phenyl-1,5-diaza-3,7-diphosphacyclooctane). Here, peak analysis, foot-of-the-wave plateau current analysis applied data sets voltammetric response recorded strength, rate constants transfer cycle. Further, case study illustrates complementary spectroscopic methods bolster mechanistic assignment. Collectively, these two showcase detailed inform rate-limiting catalysis other processes underpinning catalysis.Second, present centered [NiII(P2PhN2Bn)2]2+ (P2PhN2Bn 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane). nonaqueous Pourbaix theory extract information introduced, construction coupled diagram detailed. This identifies ligand-based protonation places influences mechanism.Together, work showcases utility disentangle complex parameters Through presentation underpin analyses, seeks adoption community thermochemical, small-molecule activation.

Язык: Английский

---

Improving Active Site Local Proton Transfer in Porous Organic Polymers for Boosted Oxygen Electrocatalysis

Angewandte Chemie International Edition, Год журнала: 2024, Номер 63(47)

Опубликована: Авг. 15, 2024

Abstract Improving proton transfer is vital for electrocatalysis with porous materials. Although several strategies are reported to assist in channels, few studies dedicated improving at the local environments of active sites Herein, we report on new Co‐corrole‐based organic polymers (POPs) improved electrocatalytic oxygen reduction reaction (ORR) and evolution (OER). By tuning pore sizes installing relays Co corrole sites, designed synthesized POP‐2‐OH both channels sites. This POP shows remarkable activity ORR E 1/2 =0.91 V vs RHE OER η 10 =255 mV. Therefore, this work significant present a strategy improve site materials highlight key role such structural functionalization boosting electrocatalysis.

Язык: Английский

---

Direct Electrochemical Conversion of CO₂ Sorbent Solution to Formate by a Molecular Iron Catalyst

ACS Energy Letters, Год журнала: 2024, Номер 9(6), С. 2896 - 2901

Опубликована: Май 22, 2024

The reactive capture of CO2 (RCC) is the direct conversion to a product that performed in sorbent where has been captured and stored. Here, we report molecular cluster electrocatalyst [Fe4N(CO)12]− (1–) can be used for RCC produce formate with 89% faradaic efficiency. In this integrated process, solution monoethanolamine (MEA) water ratio 30:70 added 0.1 M KHCO3 serves dual purpose as reaction electrochemical reduction CO2. Under 1 atm CO2, buffered at pH = 7.9 HCO3–/CO32–, loading 2.67 M. Mechanistic studies using cyclic voltammetry indicate dissolved substrate. insights into heterogeneous processes are also discussed.

Язык: Английский

---

Mechanistic insight into electrocatalytic CO2 reduction to formate by the iron(I) porphyrin complex: A DFT study

Molecular Catalysis, Год журнала: 2024, Номер 566, С. 114430 - 114430

Опубликована: Авг. 7, 2024

Язык: Английский

---

Circumventing Kinetic Barriers to Metal Hydride Formation with Metal–Ligand Cooperativity

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(44), С. 30020 - 30032

Опубликована: Окт. 23, 2024

We report the two-electron, one-proton mechanism of cobalt hydride formation for conversion [CoIIICp(PPh2NBn2)(CH3CN)]2+ to [HCoIIICp(PPh2NBn2)]+. This complex catalytically converts CO2 formate under reduction conditions, with as a key elementary step. Through combination electrochemical measurements, digital simulations, theoretical calculations, and additional mechanistic thermochemical studies, we outline explicit role PPh2NBn2 ligand in proton-coupled electron transfer (PCET) reactivity that leads formation. reveal three unique PCET mechanisms, show amine on serves kinetically accessible protonation site en route thermodynamically favored hydride. Cyclic voltammograms recorded proton sources span wide range pKa values four distinct regimes where changes function acid strength, concentration, timescale between steps. Peak shift analysis was used determine rate constants applicable. work highlights astute choices must be made when designing catalytic systems, including basicity kinetic accessibility sites, steps, maximize catalyst stability efficiency.

Язык: Английский

---

Engineering the regulation strategy of active sites to explore the intrinsic mechanism over single‑atom catalysts in electrocatalysis

Journal of Colloid and Interface Science, Год журнала: 2025, Номер 693, С. 137595 - 137595

Опубликована: Апрель 14, 2025

Язык: Английский

---

Proton-Modulated Nickel Hydride Electrocatalysis for the Hydrogenation of Unsaturated Bonds and Olefin Isomerization

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Апрель 21, 2025

Transition-metal hydrides stand as indispensable intermediates in both energy conversion and organic synthesis. Their electrochemical generation represents a compelling sustainable approach, enabling precise control over the reactivity expanding scope of electrocatalytic hydrogenation isomerization. However, major challenge Ni-catalyzed is competing hydrogen evolution reaction (HER), which has led to various innovative strategies aimed at circumventing Ni-H formation. Here, we pursued an alternative approach by designing bifunctional ligand with pendant amine moiety promote This design enabled selective (semi)hydrogenation diverse range substrates, including terminal internal alkynes, alkenes, aldehydes, achieving unprecedented substrate scope. Remarkably, also demonstrated tunable positional selectivity for olefin isomerization employing different types proton sources. Our method exhibits excellent functional group tolerance, streamlining access pharmaceuticals their derivatives. Computational studies revealed crucial, noninnocent role source modulating metal hydride selectivity, either through bonding, direct protonation amine, or facilitation protodemetalation.

Язык: Английский

---

Impact of Pendant Amine Basicity on Electrochemically-Promoted Cobalt Hydride Formation: Kinetic and Mechanistic Analysis

Inorganic Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Май 15, 2025

We report the role of pendant amine basicity on proton-coupled electron transfer (PCET) reactivity for conversion [CoIIICp(PPh2NR2)(CH3CN)]2+ complexes to [HCoIIICp(PPh2NR2)]+, which is a key transformation involved in catalytic CO2 formate and H2 evolution. Three were studied, where substituent (R) varies from benzyl, methoxyphenyl, or phenyl. In previous work benzyl system, we showed that PPh2NBn2 ligand serves as kinetically accessible protonation site enables three participating hydride formation mechanisms. this work, combination electrochemical measurements theoretical calculations used show electronic donation at influences PCET mechanism proton kinetics related cobalt under analogous reaction conditions. Notably, with most electron-donating correlates lowest barrier protonation, specific mechanisms can be shut off least substituent. The mechanistic kinetic changes upon modulation have great implications overall efficiency selectivity, especially generate intermediate selective reduction formate. This shows how exploit using ligand-cooperative design facilitate reactions energy transformations.

Язык: Английский

---