High-Performance and Durable Pd<sub>5</sub>P<sub>2</sub>/PdP<sub>2</sub> Heterointerface for All-pH Hydrogen Evolution Reactions
Zhenbo Guo, Ying Cui, Wei Liu
Abstract
Palladium (Pd) phosphides are considered a kind of highly promising catalytic material as a Pt alternative for the hydrogen evolution reaction (HER). However, well-studied Pd phosphide catalysts still suffer from sluggish HER kinetics because of the inappropriate adsorption strengths of hydrogen and water. Herein, we synthesized a kind of Pd 5 P 2 /PdP 2 heterogeneous nanoparticle catalyst with a good HER performance in both acidic (η 10 = 28 mV, η 500 = 150 mV) and alkaline electrolytes (η 10 = 31.2 mV, η 500 = 180 mV). Moreover, Pd 5 P 2 /PdP 2 @CNTs exhibit a low Tafel slope value of 24.3 mV dec –1 and a high turnover frequency value of 38.9 s –1 at 100 mV in 0.5 M H 2 SO 4, which are one of the best catalysts for HER in the reported state-of-the-art noble metal-based electrocatalysts. In addition, the flow-type water electrolyzers [PdP 2 /Pd 5 P 2 @CNTs(−)||S–NiFe-LDH(+)] and [PdP 2 /Pd 5 P 2 @CNTs(−)||IrO 2 (+)] were operated successfully with a low cell voltage of 1.71 and 1.75 V at 75 °C, respectively, in acidic and alkaline electrolytes, which can also be driven by a solar cell cart without additional energy applied, even at an industrial current density of 500 mA cm –2 . In situ Raman and temperature-programmed desorption experiments demonstrate that the moderate H 2 O absorption strength and faster H 2 desorption kinetics on the PdP 2 /Pd 5 P 2 heterojunction promote water dissociation and the release of H 2, thereby improving its HER performance. This work highlights a heterogeneous interface modulation design principle, which may inspire the development of more advanced HER catalysts.