Electrocatalytic oxidation of ethanol and ethylene glycol on cubic, octahedral and rhombic dodecahedral palladium nanocrystals

Cubic, octahedral and rhombic dodecahedral Pd nanocrystals were synthesized and examined as nanocatalysts for electro-oxidation of ethanol and ethylene glycol. Combined electrochemical measurements and density functional theory calculations reveal that nanofacet-dependent affinity and reactivity of OHads and COads are closely linked to the C2 alcohol oxidation activities, with the highest reactivity found on the Pd nanocubes bounded by {100} facets

Li Electrochemical Tuning of Metal Oxide for Highly Selective CO₂ Reduction

Engineering active grain boundaries (GBs) in oxide-derived (OD) electrocatalysts is critical to improve the selectivity in CO₂ reduction reaction (CO₂RR), which is becoming an increasingly important pathway for renewable energy storage and usage. Different from traditional <i>in situ</i> electrochemical reduction under CO₂RR conditions, where some metal oxides are converted into active metallic phases but with decreased GB densities, here we introduce the Li electrochemical tuning (LiET) method to controllably reduce the oxide precursors into interconnected ultrasmall metal nanoparticles with enriched GBs. By using ZnO as a case study, we demonstrate that the LiET-Zn with freshly exposed GBs exhibits a CO₂-to-CO partial current of ∼23 mA cm^–2 at an overpotential of −948 mV, representing a 5-fold improvement from the OD-Zn with GBs eliminated during the <i>in situ</i> electro-reduction process. A maximal CO Faradaic efficiency of ∼91.1% is obtained by LiET-Zn on glassy carbon substrate. The CO₂-to-CO mechanism and interfacial chemistry are further probed at the molecular level by advanced <i>in situ</i> spectroelectrochemical technique, where the reaction intermediate of carboxyl species adsorbed on LiET-Zn surface is revealed

B‑Doped Pd Catalyst: Boosting Room-Temperature Hydrogen Production from Formic Acid–Formate Solutions

Facile production of hydrogen at room temperature is an important process in many areas including alternative energy. In this Communication, a potent boron-doped Pd nanocatalyst (Pd-B/C) is reported for the first time to boost hydrogen generation at room temperature from aqueous formic acid–formate solutions at a record high rate. Real-time ATR-IR spectroscopy is applied to shed light on the enhanced catalytic activity of B-doping and reveals that the superior activity of Pd-B/C correlates well with an apparently impeded CO_ad accumulation on its surfaces. This work demonstrates that developing new anti-CO poisoning catalysts coupled with sensitive interfacial analysis is an effective way toward rational design of cost-effective catalysts for better hydrogen energy exploitation

Surface-Enhanced Infrared Spectroscopic Study of a CO-Covered Pt Electrode in Room-Temperature Ionic Liquid

ATR-SEIRAS is extended for the first time to study potential-induced surface and interface structure variation of a CO-covered Pt electrode in a room-temperature ionic liquid of <i>N</i>-butyl-<i>N</i>-methyl-piperidinium bis­((trifluoromethyl)­sulfonyl)­imide (or [Pip₁₄]­[TNf₂]). Owing to a wide effective potential window of [Pip₁₄]­[TNf₂], a gradual conversion from bridged CO_ad (CO_B) to terminal CO_ad (CO_L) is observed in response to positively going potentials, suggesting that [Pip₁₄]⁺ may be involved in a strong electrostatic interaction with the CO_ad. This site conversion enables the ratio of the apparent absorption coefficient of CO_L to that of CO_B to be determined. Also, the spectral results reveal the potential-dependent CO_ad frequency variations as well as the potential-induced interfacial ionic reorientation and movement at the Pt/CO/[Pip₁₄]­[TNf₂] interface

Plasmon-Enhanced C–C Bond Cleavage toward Efficient Ethanol Electrooxidation

Ethanol, as a sustainable biomass fuel, is endowed with the merits of theoretically high energy density and environmental friendliness yet suffers from sluggish kinetics and low selectivity toward the desired complete electrooxidation (C1 pathway). Here, the localized surface plasmon resonance (LSPR) effect is explored as a manipulating knob to boost electrocatalytic ethanol oxidation reaction in alkaline media under ambient conditions by appropriate visible light. Under illumination, Au@Pt nanoparticles with plasmonic core and active shell exhibit concurrently higher activity (from 2.30 to 4.05 A mgPt–1 at 0.8 V vs RHE) and C1 selectivity (from 9 to 38% at 0.8 V). In situ attenuated total reflection–surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) provides a molecular level insight into the LSPR promoted C–C bond cleavage and the subsequent CO oxidation. This work not only extends the methodology hyphenating plasmonic electrocatalysis and in situ surface IR spectroscopy but also presents a promising approach for tuning complex reaction pathways

Boosting electrocatalytic oxidation of formic acid on SnO₂-decorated Pd nanosheets

Formic acid (HCOOH), as a natural biomass, is a promising feedstock for low temperature fuel cells, and rational development of efficient catalysts for electrochemical dehydrogenation of HCOOH plays a key role toward its full chemical energy utilization. Herein, Pd nanosheets decorated with SnO2 nanoflakes (denoted hereafter as Pd@SnO2-NSs) are designed as a composite catalyst, showing superior performance for formic acid electro-oxidation, as compared to pristine Pd nanosheets (Pd-NSs). In situ attenuated total reflection infrared (ATR-IR) spectroscopic results suggest a promoted formate pathway on the Pd@SnO2-NSs with a suppressed accumulation of CO poisoning species. DFT calculations further indicate that the Pd (111) surface modified with SnO2 has lower energy barriers for the bidentate formate formation, the bidentate to monodentate formate transformation and the C-H bond scission

Supplementary information files for Boosting electrocatalytic oxidation of formic acid on SnO₂-decorated Pd nanosheets

Supplementary files for article Boosting electrocatalytic oxidation of formic acid on SnO2-decorated Pd nanosheets. Formic acid (HCOOH), as a natural biomass, is a promising feedstock for low temperature fuel cells, and rational development of efficient catalysts for electrochemical dehydrogenation of HCOOH plays a key role toward its full chemical energy utilization. Herein, Pd nanosheets decorated with SnO2 nanoflakes (denoted hereafter as Pd@SnO2-NSs) are designed as a composite catalyst, showing superior performance for formic acid electro-oxidation, as compared to pristine Pd nanosheets (Pd-NSs). In situ attenuated total reflection infrared (ATR-IR) spectroscopic results suggest a promoted formate pathway on the Pd@SnO2-NSs with a suppressed accumulation of CO poisoning species. DFT calculations further indicate that the Pd (111) surface modified with SnO2 has lower energy barriers for the bidentate formate formation, the bidentate to monodentate formate transformation and the C-H bond scission

Supplementary information file for article: 'Electrocatalytic oxidation of ethanol and ethylene glycol on cubic, octahedral and rhombic dodecahedral palladium nanocrystals'

Supplementary information file for article: 'Electrocatalytic oxidation of ethanol and ethylene glycol on cubic, octahedral and rhombic dodecahedral palladium nanocrystals'.Abstract: Cubic, octahedral and rhombic dodecahedral Pd nanocrystals were synthesized and examined as nanocatalysts for electro-oxidation of ethanol and ethylene glycol. Combined electrochemical measurements and density functional theory calculations reveal that nanofacet-dependent affinity and reactivity of OHads and COads are closely linked to the C2 alcohol oxidation activities, with the highest reactivity found on the Pd nanocubes bounded by {100} facets.</div

Boosting Formate Production in Electrocatalytic CO₂ Reduction over Wide Potential Window on Pd Surfaces

Facile interconversion between CO₂ and formate/formic acid (FA) is of broad interest in energy storage and conversion and neutral carbon emission. Historically, electrochemical CO₂ reduction reaction to formate on Pd surfaces was limited to a narrow potential range positive of −0.25 V (vs RHE). Herein, a boron-doped Pd catalyst (Pd–B/C), with a high CO tolerance to facilitate dehydrogenation of FA/formate to CO₂, is initially explored for electrochemical CO₂ reduction over the potential range of −0.2 V to −1.0 V (vs RHE), with reference to Pd/C. The experimental results demonstrate that the faradaic efficiency for formate (η_HCOO^–) reaches ca. 70% over 2 h of electrolysis in CO₂-saturated 0.1 M KHCO₃ at −0.5 V (vs RHE) on Pd–B/C, that is ca. 12 times as high as that on homemade or commercial Pd/C, leading to a formate concentration of ca. 234 mM mg^–1 Pd, or ca. 18 times as high as that on Pd/C, without optimization of the catalyst layer and the electrolyte. Furthermore, the competitive selectivity η_HCOO^–/η_CO on Pd–B/C is always significantly higher than that on Pd/C despite a decreases of η_HCOO^– and an increases of the CO faradaic efficiency (η_CO) at potentials negative of −0.5 V. The density functional theory (DFT) calculations on energetic aspects of CO₂ reduction reaction on modeled Pd(111) surfaces with and without H-adsorbate reveal that the B-doping in the Pd subsurface favors the formation of the adsorbed HCOO*, an intermediate for the FA pathway, more than that of *COOH, an intermediate for the CO pathway. The present study confers Pd–B/C a unique dual functional catalyst for the HCOOH ↔ CO₂ interconversion

Electrocatalytic Activities of Oxygen Reduction Reaction on Pd/C and Pd–B/C Catalysts

The investigation of electrocatalysis of oxygen reduction reaction (ORR) on non-Pt electrodes is of great interest to address the current technical bottleneck of using costly and rare metal Pt in the cathodes of low-temperature fuel cells. The present work presents a comparative study of ORR on carbon supported Pd and B-doped Pd (with ca. 7 at. % B doping) nanocatalysts with well-controlled particle sizes, dispersions, and loadings (both with 20 wt % Pd). It is found that the Pd–B/C exhibits a modestly higher electrocatalytic activity toward ORR: the specific activity is enhanced by factors of ca. 2.0 and 2.7 on Pd–B/C as compared to that on Pd/C in acidic media at 0.85 and 0.90 V, respectively. In contrast, the corresponding enhancement factors are ca. 1.3 and 1.6, respectively, in alkaline media. To understand the promoted ORR activity by B-doping, density functional theory (DFT) calculations are applied, revealing weakened adsorption of the O-containing species on B-doped Pd surfaces, consistent with the XPS and CO stripping results. Despite the modest improvement at this moment, it raises the hope of further developing Pd-based ORR catalysts as well as the concern of reasonable comparison of two sets of non-Pt catalysts