Laser-Assisted Synthesis of Pd Aerogel with Compressive Strain for Boosting Formate and Ethanol Electrooxidation

Abstract

Owing to the increasing energy demands, direct small-molecule fuel cells, such as ethanol and formate fuel cells, have attracted great attention. During the operation of the fuel cell, noble metal catalysts are widely used to accelerate the reaction kinetics by alloying with other materials. However, there are a few facile methods for improving elemental metal catalytic activity. In this work, the defect-rich palladium (Pd) aerogels are acquired by laser ablating technology, which can significantly improve the intrinsic activity of Pd elementary catalysts through introducing defects and lattice strain. The electrochemical results show that the mass and specific activities of the obtained Pd aerogel for the formate oxidation reaction are 2.26 and 1.99 times higher than those of the commercial Pd/C. The excellent activity and stability of the Pd aerogel for ethanol oxidation reaction have also been demonstrated. The effect of the compressive strain is further investigated by density functional theory (DFT) calculations. It has been found that the compressive strain weakens the adsorption strength of the intermediates, which can facilitate the desorption of toxic specifics. The laser-assisted synthesis of defect-rich aerogel paves a way in optimizing the structure of the elemental metal catalysts and improving their intrinsic catalytic activity.

Diverse nanomaterials synthesized by laser ablation of pure metals in liquids

“…Recently, Zhang et al [333] synthesized Pd-aerogel composite catalysts and revealed their advantages of compressive strains to boost their applications for formate and ethanol electrooxidation. Figure 21(a) displays the synthesis procedures including in situ LAL in the presence of trisodium citrate (NaCA), ex situ addition of ascorbic acid (AA), and colloid aging.…”

“…Without citrates, the size of Pd particles is as large as 11.3 nm. Given their higher specific surface area and the existence of compressive strains, Pd aerogel is more active than Pd/C for formate electrooxidation with mass and specific activities 2.26/1.99 times higher than those of commercial Pd/C catalysts [333]. Supported Pd composite catalysts have been prepared by in situ LAL in MWCNTs-containing solutions [334] and ex situ mixing of a biowaste extraction of calcium lignosulfonate for catalytic energy storage [335].…”

“…Downsizing bulky Al into nanoscale can significantly lower the enthalpy of Al Copied from ref. [333] with permission. materials from −1675 kJ/mol (bulky Al) to −2324 kJ/mol for a single Al atom.…”

“…(b)-(e) TEM images of LAL-synthesized Pd NPs and Pd-aerogel composites after different periods of aging. Insets in (b)-(e) are size histograms.Copied from ref [333]. with permission.…”

Combining surface chemical functionalization with introducing reactive oxygen species boosts ethanol electrooxidation

“…As shown in Fig. 5C, the current densities for all the tested catalysts initially decayed rapidly due to the intermediate products occupying the surface sites of catalysts and then became almost stable after 1200 s. 35 It is noteworthy that the current density decay rate of Pd-CeO 2−x /FGS is lower than those of Pd-CeO 2−x /GS, Pd/ FGS, Pd/GS and Pd/C, respectively. Moreover, the steady-state current density ( j s ) of Pd-CeO 2−x /FGS is 96.3 mA mg −1 after 7200 s, which is higher than that of Pd-CeO 2−x /GS (77.7 mA mg −1 ), Pd/FGS (63.7 mA mg −1 ), Pd/GS (27.4 mA mg −1 ) and Pd/ C (7.7 mA mg −1 ), respectively (Fig.…”