Role of Ni in PtNi Bimetallic Electrocatalysts for Hydrogen and Value-Added Chemicals Coproduction via Glycerol Electrooxidation

Abstract

Pt-based bimetallic electrocatalysts are promising candidates to convert surplus glycerol from the biodiesel industry to value-added chemicals and coproduce hydrogen. It is expected that the nature and content of the elements in the bimetallic catalyst can not only affect the reaction kinetics but also influence the product selectivity, providing a way to increase the yield of the desired products. Hence, in this work, we investigate the electrochemical oxidation of glycerol on a series of PtNi nanoparticles with increasing Ni content using a combination of physicochemical structural analysis, electrochemical measurements, operando spectroscopic techniques, and advanced product characterizations. With a moderate Ni content and a homogenously alloyed bimetallic Pt−Ni structure, the PtNi2 catalyst displayed the highest reaction activity among all materials studied in this work. In situ FTIR data show that PtNi2 can activate the glycerol molecule at a more negative potential (0.4 V RHE ) than the other PtNi catalysts. In addition, its surface can effectively catalyze the complete C−C bond cleavage, resulting in lower CO poisoning and higher stability. Operando X-ray absorption spectroscopy and UV−vis spectroscopy suggest that glycerol adsorbs strongly onto surface Ni(OH) x sites, preventing their oxidation and activation of oxygen or hydroxyl from water. As such, we propose that the role of Ni in PtNi toward glycerol oxidation is to tailor the electronic structure of the pure Pt sites rather than a bifunctional mechanism. Our experiments provide guidance for the development of bimetallic catalysts toward highly efficient, selective, and stable glycerol oxidation reactions.

Perovskite oxides as an opportunity to systematically study the Electrooxidation of alcohols and Polyols on materials based on abundant elements: Learning from the experience using pure metals and metallic oxides in (Electro-)catalysis

“…However, the use of pump-probe systems 222 and of shinners 223 opens new opportunities for the application of Raman spectroscopy in electrocatalysis 224 . In addition, considering the results showed in this work, we believe that in situ optical-electrochemical spectra can bring important insights about the formation of oxygenated species on the catalysts surface 225 .…”

Perovskite Oxides as an Opportunity to Systematically Study the Electrooxidation of Alcohols and Polyols on Materials Based on Abundant Elements: Learning from the Experience Using Pure Metals and Metallic Oxides in Electrocatalysis

“…222 In addition, considering the results shown in this work, we believe that in situ optical−electrochemical spectra can bring important insights into the formation of oxygenated species on the catalyst's surface. 223 Finally, techniques employing X-rays in synchrotrons can render the most valuable information about the structure and electronic configuration of these materials under in situ conditions. 224,225 For example, by performing X-ray absorption fine structure measurements, we can follow the oxidation state of an element (among other properties) in the function of the electrochemical potentials during the reaction, 217 which has proven to be essential for the electrooxidation of organics on metal oxides.…”

“…However, the use of pump–probe systems and of shinners opens new opportunities for the application of Raman spectroscopy in electrocatalysis . In addition, considering the results shown in this work, we believe that in situ optical–electrochemical spectra can bring important insights into the formation of oxygenated species on the catalyst’s surface …”

Development of Electrochemical Cells and Their Application for Spatially Resolved Analysis Using a Multitechnique Approach: From Conventional Experiments to X-Ray Nanoprobe Beamlines

“…The usage of X-rays may excel at structure and stability analysis, but it lacks the ability to evaluate activity and selectivity. On the other hand, spectroscopic techniques such as in situ FTIR and Raman are compelling at probing selectivity/activity. − Vibrational spectroscopy can be used to analyze key species at the electrical double layer, including the electrocatalytic material, adsorbate–electrode intermediate species, and also reaction products . In addition, this information can be used in time-dependent studies to infer the (electro-)­catalyst stability …”