Unveiling the effect of shapes and electrolytes on the electrocatalytic ethanol oxidation activity of self-standing Pd nanostructures
Adewale K. Ipadeola, Belal Salah, Alaa Ghanem, Doniyorbek Ahmadaliev, M. A. Sharaf, Aboubakr M. Abdullah, Kamel Eid
Abstract
Morphologically controlled Pd-based nanocrystals are the most efficient strategies for improving the electrocatalytic ethanol oxidation reaction (EOR) performance; however, their morphological-EOR activity relationship and effect of electrolytes at a wide pH range are still ambiguous. Here, we have synthesized porous self-standing Pd clustered nanospheres (Pd-CNSs) and Pd nanocubes (Pd-NCBs) for the EOR in acidic (H 2 SO 4 ), alkaline (KOH), and neutral (NaHCO 3 ) electrolytes compared to commercial spherical-like Pd/C catalysts. The fabrication process comprises the ice-cooling reduction of Pd precursor by sodium borohydride (NaBH 4 ) and l-ascorbic acid to form Pd-CNSs and Pd-NCBs, respectively. The EOR activity of Pd-CNSs significantly outperformed those of Pd-NCBs, and Pd/C in all electrolytes, but the EOR activity was better in KOH than in H 2 SO 4 and NaHCO 3 . This is due to the 3D porous clustered nanospherical morphology that makes Pd active centers more accessible and maximizes their utilization during EOR. The EOR specific/mass activities of Pd-CNSs reached (8.51 mA/cm 2 /2.39 A/mg Pd ) in KOH, (2.98 mA/cm 2 /0.88 A/mg Pd ) in H 2 SO 4 , and (0.061 mA/cm 2 /0.0083 A/mg Pd ) in NaHCO 3 , in addition to stability after 1000 cycles. This study affirms that porous 3D spherical Pd nanostructures are preferred for the EOR than those of 0D spherical-like and multi-dimensional cube-like nanostructures.