Formic Acid Electro-oxidation Catalyzed by PdNi/Graphene Aerogel

Abstract

Direct formic acid fuel cells involve two significant half-reactions, namely formic acid electro-oxidation and oxygen reduction reaction, and the more sluggish and complex process for anode formic acid oxide also determine the whole fuel cells energy conversion efficiency. The most efficient catalysts rely on the noble metal of Pt and Pd based catalysts and compared with Pt catalysts, Pd catalyst is more appealing because of the low CO poisoning effect during the electro-oxidation of formic acid that mainly follows the direct pathway. The Pd alloy effect and support effect should be considered for the catalyst fabrication since the resulted structure and electronic modification could largely increase the catalytic performance. Graphene emerges out as novel support while the easy agglomeration and destruction of pure graphene do not guarantee promising merits. In this work, we demonstrated the formic acid oxidation ability boosting by facile coupling PdNi alloy and 3D graphene aerogel (PdNi/GA) via a freezingdrying/thermal annealing reduction approach. The PdNi alloy crystal structure was well confirmed by the X-ray diffractions technique and the alloy nanoparticles were successfully anchored on the 3D graphene aerogel surface. The electrochemical performance was evaluated for formic acid oxidation in the acid electrolyte. The PdNi/GA catalyst displayed a larger peak current density of 136 mA•cm −2 , which was 2 and 3.45 times greater than Pd/GA (68 mA•cm −2 ) and Pd/C (39.4 mA•cm −2 ), respectively. The anti-CO poisoning ability was measured by CO stripping technique, and a low onset potential of 0.49 V was found on PdNi/GA catalyst, about 120 mV less than that of Pd/GA catalyst, indicating the oxophilic property of Ni to assist formic acid oxidation via the bi-functional mechanism. The oxidation peak potential of 0.67 V was observed on PdNi/GA, about 40 mV less than that of Pd/C catalyst, indicating the merits of 3D structure of graphene. Moreover, PdNi/GA catalyst had the highest mass activity of 1699 mA•mg −1 compared to Pd/GA (851 mA•mg −1 ) and Pd/C (537 mA•mg −1 ) catalysts. The specific activity of PdNi/GA was 2.6 mA•cm −2 , which was 1.94 and 2.7 times of Pd/GA (1.34 mA•cm −2 ) and Pd/C (0.96 mA•cm −2 ) catalysts. The highly improved catalytic performance could be due to the combined alloy and support effect. The PdNi/GA was a promising catalyst for application in the direct formic acid fuel cells.

Strong Metal–Support Interaction over PtPdCu/Al2O3 toward Hydrogenation of Nitrobenzene

“…In contrast, the Cu 2p binding energies of PtPdCu-185 and PtPdCu-300 exhibit shift to higher energies by the values of 0.7 and 1.6 eV with respect to that for PtPdCu-RT, respectively, which suggests that electronic charge partially transfers from Cu to other components. As shown in Figure B, the binding energy of Pd 3d 5/2 in the PtPdCu-RT catalyst is determined to be 334.6 eV, which is consistent with standard binding energy of metallic Pd. , The Pd 3d 5/2 shift to 335.0 and 335.5 eV following 185 and 300 °C annealing treatment. In terms of Pt 4d in the PtPdCu-RT (Figure B), the Pt 4d 5/2 and Pt 4d 3/2 with binding energies of 314.0 and 330.8 eV, respectively, are attributed to metallic Pt, while the Pt 4d binding energies of PtPdCu-185 and PtPdCu-300 shift to higher energies with values of 0.4 and 0.7 eV, respectively.…”

“…As shown in Figure 3B, the binding energy of Pd 3d 5/2 in the PtPdCu-RT catalyst is determined to be 334.6 eV, which is consistent with standard binding energy of metallic Pd. 2,32 The Pd 3d 5/2 shift to 335.0 and 335.5 eV following 185 and 300 °C annealing treatment. In terms of Pt 4d in the PtPdCu-RT (Figure 3B), the Pt 4d 5/2 and Pt 4d 3/2 with binding energies of 314.0 and 330.8 eV, respectively, are attributed to metallic Pt, 33 while the Pt 4d binding energies of PtPdCu-185 and PtPdCu-300 shift to higher energies with values of 0.4 and 0.7 eV, respectively.…”

Pt/Mn3O4 cubes with high anti-poisoning ability for C1 and C2 alcohol fuel oxidation

“…160 and 180 mV for the Pt-Mn 3 O 4 catalyst (Table S5, ESI †), indicating its largely improved catalytic ability to realize the oxidation and removal of poisoning intermediates. 22,23 This set of results was consistent with the XPS results where the electron enrichment of the surfaces of the Pt particles was concluded according to d-band theory to weaken the adsorption of poisoning CO This journal is © The Royal Society of Chemistry 2022 intermediates. 24,25 The higher the d-state in energy relative to the Fermi level, the emptier the anti-bonding state and the higher the adsorption energy between the adsorbate and metal surface.…”

A PtPdCoCuNi high-entropy alloy nanocatalyst for the hydrogenation of nitrobenzene

“…S6B † ) are located at 334.5 and 339.8 eV, respectively, associated with metallic Pd. 19 The binding energy of Co 2p 3/2 (Fig. S6C † ) is about 778.5 eV, which is consistent with metallic Co. 20 The Cu 2p 3/2 and Cu 2p 1/2 (Fig.…”