High-efficiency recovery of palladium and platinum using black phosphorus for in-situ synthesis of long-term stable hydrogen evolution catalysts

Abstract

The reserves of palladium (Pd) and platinum (Pt) are scarce and require sophisticated processing. Herein, a three-stage recovery process with black phosphorus (BP) is established in this study to recover Pd and Pt from spent catalysts, presenting a promising strategy for addressing the precious metals crisis. The recovery efficiency of Pd is 99.36 % ± 0.08 % after two stages, with a total recovery capacity of 1426.11 ± 1.73 mg Pd g−1 BP, which is 90 times higher than that of the latest technologies. The overall recovery efficiency of Pt (II) is 98.62 % (467.91 mg Pt g−1 BP) after the third stage (45 °C, 30 min). Furthermore, the current density of the optimal catalysts generated in the first stage (weight ratio: Pd:Pt = 4.9:1) is the highest (57.61 mA cm−1; overpotential = 70 mV vs. RHE) among the catalysts generated in the second (Pd:Pt = 1:1) and third (Pd:Pt = 1:11) stages. Pd/Pt–BP generated in the first stage further achieved remarkable long-term stability of 225 h (10 mA cm−2) and exhibited maximum durability of > 400 h. Owing to the reduced capability and activation of BP to metals, immobilized Pd (II) and Pt (II) are recovered and directly converted to long-term stable hydrogen evolution catalysts without complex processing.