Designing an Electron-Deficient Pd/NiCo₂O₄ Bifunctional Electrocatalyst with an Enhanced Hydrodechlorination Activity to Reduce the Consumption of Pd

Abstract

Reducing the Pd loading on electrodes is critical in the electrocatalytic hydrodechlorination (EHDC) of chlorinated organic compounds (COCs). The EHDC reaction of COCs on Pd involves three steps: H* formation, H* adsorption, and dechlorination. It has been established that the initial hydrogen evolution reaction (HER) occurs on Pd0 and the dechlorination steps occur on Pd2+. A strategy is proposed to design new electrodes by adding a reducible HER-active interlayer to replace Pd0, fulfilling the responsibility of producing hydrogen, and to facilitate the formation of more Pd2+ for following C–Cl bond cleavage. Keeping the atomic hydrogen adsorption energy on the Pd/interlayer similar to that on pure Pd is also necessary for H* adsorption as well as to maintain a high EHDC activity. For the first time, the NiCo2O4-interlayer-modified Pd/Ni-foam electrode was applied in the EHDC of COCs, which enhanced the EHDC efficiency to 100% within 90 min and reduced 88.6% of Pd consumption. The Pd/NiCo2O4/Ni-foam electrode with enhanced EHDC activity was also observed with almost 100% product selectivity and good stability. A synergistic mechanism is proposed for the enhanced EHDC activity on the Pd/NiCo2O4/Ni-foam. This work offers a simple and useful strategy to design robust electrocatalysts for the EHDC of COCs.

Coincorporation of N and S into Zero-Valent Iron to Enhance TCE Dechlorination: Kinetics, Electron Efficiency, and Dechlorination Capacity

“…Surface reactions strongly mediate reductive dechlorination of CHCs with ZVI particles. It has been well established that bimetals could generate H atoms 33 through HER and ultimately contribute to efficient reductive dechlorination, while S-ZVI could mediate fast electron transfer from the Fe 0 core to the particle surface and thus increase the rate of reductive dechlorination. However, surface reactions between modified ZVI and target CHCs are poorly understood due to the variation of surface compositions; detection and quantification of reaction products are not the focus of most studies.…”

Defective Layered Double Hydroxide Nanosheet Boosts Electrocatalytic Hydrodechlorination Reaction on Supported Palladium Nanoparticles

“…As observed in Figure 2c,d, the Pd/Ni x Al 100−x -LDH-OH v hybrid structure enables not only the formation of electrondefective Pd species (Pd δ+ ) but also the inclusion of OH v sites. 16,21 The much higher activity of OH v -free Pd/Ni(OH) 2 than Pd/C (Figure 3c) tells that the Pd δ+ sites is the dominative origin of the enhanced EHDC, benefiting from its superior performance in cleaving the C−Cl bond. 16,21 Nevertheless, it is observed in Figures 2d and 3c that the estimated OH v content and EHDC activity of Pd/Ni x Al 100−x -LDH-OH v display a close volcano-like varying trend with x, suggesting that the OH v also plays a crucial role in EHDC.…”

“…16,21 The much higher activity of OH v -free Pd/Ni(OH) 2 than Pd/C (Figure 3c) tells that the Pd δ+ sites is the dominative origin of the enhanced EHDC, benefiting from its superior performance in cleaving the C−Cl bond. 16,21 Nevertheless, it is observed in Figures 2d and 3c that the estimated OH v content and EHDC activity of Pd/Ni x Al 100−x -LDH-OH v display a close volcano-like varying trend with x, suggesting that the OH v also plays a crucial role in EHDC. 29 To compare the efficacy of OH v and Pd δ+ in promoting EHDC, the EHDC performance of Pd/Ni 67 Al 33 -LDH-OH v is further examined after quenching its OH v by immersing the electrode in PO 4 3− aqueous solution, given the strong complexing bond of PO 4 3− with the exposed Ni 2+ .…”

“…6,7 Current work primarily focuses on strategies to optimize the geometric and electronic states of Pd for intensified H* generation, which is dedicated to boosting the EHDC reaction and raising the atomic utilization efficiency of Pd. 8 Engineering Pd into nanowire/nanosheet structures, 9,10 alloying Pd with a promoting metal (Ag, In, and Cu), 11,12 constructing Pd-support interfaces (Pd−MnO 2 , 13 Pd−TiO 2 , 14 Pd−C 3 N 4 , 15 Pd−Ni 2 CoO 4 , 16 and Pd−TiN/TiC 17 ), decorating Pd with organic ligands, 18 sites 16,19−21 have all suggested to be efficient in affording high EHDC efficiencies. Despite these findings, little attention has been given to the H + supply chain.…”

A Protocol for Electrocatalyst Stability Evaluation: H2O2 Electrosynthesis for Industrial Wastewater Treatment

“…Electrocatalysis has emerged into the limelight of academic interest as a propitious option for industrial wastewater treatment designed to ameliorate these concerns. − Such technologies can chemically transform a myriad of harmful pollutants into benign products via direct electron transfer at the active sites or through the production of oxidants for reaction. They may operate under ambient conditions, do not require auxiliary chemicals, and are versatile; electrocatalytic reactors may be implemented as standalone systems or accommodate existing treatment trains as supplementary units. , The keen interest in electrocatalysts for treating wastewater is reflected in the meteoric rise in the number of related publications, many of which are dedicated toward the development of novel catalytic materials. − Tuning the electrochemical properties of these materials is essential to achieving high levels of pollutant removal and treatment capacity, as doing so dictates their activity and selectivity toward the redox pathway of interest.…”