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

Nejc Hodnik,Karl J J Mayrhofer,Claudio Baldizzone,Simon Geiger,Serhiy Cherevko,Aleksandar Zeradjanin,George Polymeros,Andrea Mingers,Jan-Philipp Grote

doi:10.1038/ncomms13164

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.

Highlights

The recycling of precious metals, for example, platinum, is an essential aspect of sustainability for the modern industry and energy sectors
To demonstrate and explore the effectiveness of this new approach, we initially focus on a commercial Pt black catalytic system
The study firstly verifies our conceptual framework by monitoring the electrode potentials and dissolution of Pt in the defined system of scanning flow cell (SFC)[21,29]

Summary

Introduction

The recycling of precious metals, for example, platinum, is an essential aspect of sustainability for the modern industry and energy sectors. 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. For example, US, Japan and EU, have already recognized this risk and, for the past several years are actively involved in the design of new policies, and strategies to secure reliable and unhindered access to so-called critical raw materials (CRM) In this scenario, the chemistry of recycling of platinum and other CRMs from end-of-life products, referred as urban-mining, will become more important than ever. 1.2 V versus reversible hydrogen electrode (RHE) for Pt)[20] These processes are only effective at elevated temperatures and with continuous consumption of extremely concentrated acids, as, for example, aqua regia loses its activity relatively quickly due to the release of chlorine. The core of our approach is the so-called transient electrochemical dissolution[21] process triggered by repetitive cycling between two gases, leading to an electrodeless-induced surface potential alteration (Fig. 1)

Methods

Results

Conclusion