Platinum recycling going green via induced surface potential alteration enabling fast and efficient dissolution

Abstract

The recycling of precious metals, for example, platinum, is an essential aspect of sustainability for the modern industry and energy sectors. However, due to its resistance to corrosion, platinum-leaching techniques rely on high reagent consumption and hazardous processes, for example, boiling aqua regia; a mixture of concentrated nitric and hydrochloric acid. Here we demonstrate that complete dissolution of metallic platinum can be achieved by induced surface potential alteration, an ‘electrode-less' process utilizing alternatively oxidative and reductive gases. This concept for platinum recycling exploits the so-called transient dissolution mechanism, triggered by a repetitive change in platinum surface oxidation state, without using any external electric current or electrodes. The effective performance in non-toxic low-concentrated acid and at room temperature is a strong benefit of this approach, potentially rendering recycling of industrial catalysts, including but not limited to platinum-based systems, more sustainable.

Environmentally and Industrially Friendly Recycling of Platinum Nanoparticles Through Electrochemical Dissolution–Electrodeposition in Acid‐Free/Dilute Acidic Electrolytes

“…Hodnik et al. demonstrated an effective process that included alternation of purging ozone and carbon monoxide in mild acidic solution …”

“…demonstrated an effective processt hat included alternation of purging ozone and carbonm onoxide in mild acidic solution. [37] During the potentiodynamic dissolution process controlled by using an externalp otential (Figure 1a,b), dissolved platinum can redeposit through awell-known process (Ostwald ripening) where larger particles grow on accounto ft he smaller ones. [16,25,38,39] This leads to significant growth of the Pt nanoparticles, which reduces the efficiency of the dissolution process.…”

Platinum Dissolution and Redeposition from Pt/C Fuel Cell Electrocatalyst at Potential Cycling

“…[4][5][6][7][8][9][10][11] Those studies have revealed that Pt electrochemical dissolution is predominantly a transient phenomenon occurring due to an interplay of Pt oxidation and reduction. The amount of dissolved platinum can be manipulated via different electrochemical treatments (scan rate, width of anodic and cathodic potential window), 1 gas atmosphere, 12 electrolyte, presence of organic molecules, 6,13 alloying metals, 8,14,15 thickness of the catalyst layer, 10,16 type of support material 16 and, last but not least, by the Pt particle size. 4 Much is owed to the development of advanced on-line analytical tools, especially electrochemical scanning flow cell (SFC) in combination with inductively coupled plasma mass spectrometer (ICP-MS).…”

In situ electrochemical dissolution of platinum and gold in organic-based solvent

“…This should be considered as a drawback since many relevant environments where metals are key components, such as capacitors, sensors, electrochemical reactors, and batteries operate in pure organic or a mixture of organic and aqueous phases. Furthermore, understanding the corrosion of noble metals has started to emerge as an important issue from the perspective of environmentally friendly recycling strategies, 16 where organic solvents show much promise. [17][18][19][20] ICP-MS analysis of organic matrices is not as common as in case of aqueous matrices and presents a much greater challenge in tackling instrumental settings and several unusual spectral interferences.…”