Surface Tailoring-Modulated Bifunctional Oxygen Electrocatalysis with CoP for Rechargeable Zn–Air Battery and Water Splitting

Abstract

The transition metal phosphide (TMP)-based functional electrocatalysts are very promising for the development of electrochemical energy conversion and storage devices including rechargeable metal−air batteries and water electrolyzer. Tuning the electrocatalytic activity of TMPs is one of the vital steps to achieve the desired performance of these energy devices. Herein, we demonstrate the modulation of the bifunctional oxygen electrocatalytic activity of nitrogen-doped carbon-encapsulated CoP (CoP@NC) nanostructures by surface tailoring with ultralow amount (0.56 atomic %) of Ru nanoparticles (2.5 nm). The CoP at the core and the Ru nanoparticles on the shell have a facile charge transfer interaction with the encapsulating NC. The strong coupling of Ru with CoP@NC boosts the electrocatalytic performance toward oxygen reduction (ORR), oxygen evolution (OER), and hydrogen evolution (HER) reactions. The surface-tailored catalyst requires only 35 mV to deliver the benchmark current density of 10 mA•cm −2 for HER. A small potential gap of 620 mV between ORR and OER is achieved, making the catalyst highly suitable for the development of rechargeable zinc−air batteries (ZABs). The homemade ZAB delivers a specific capacity of 780 mA•hg Zn −1 and peak power density of 175 mW•cm −2 with a very small voltaic efficiency loss (1.1%) after 300 cycles. The two-electrode water splitting cell

Modulating the Fe spin state in FeNC catalysts by Ru nanoparticles to facilitate the oxygen reduction reaction

“…The Δ E = 0.57 V for the Ru NP @FeNC catalyst is smaller than 0.62 V of the FeNC catalyst, and a smaller window has a better bifunctional oxygen electrocatalytic performance, so the results show that the electronic structure of the active sites in the catalyst is adjusted after in situ growth of Ru, which makes the theoretical equilibrium potential closer. 30–32 Due to the excellent ORR performance of the Ru NP @FeNC catalyst, a liquid rechargeable zinc–air battery was created using polished zinc foil as the anode and carbon paper coated with a catalyst as the cathode, and a solution of 0.2 M zinc acetate and 6 M KOH as the electrolyte (Fig. 6(b)).…”