Unlocking the Potential of Single Atoms Loaded Geobacter Hybrid Catalyst as Bifunctional Electrocatalyst for Water Splitting

Single-atom metal (SA-M) catalysts with high dispersion of active metal sites allow maximum atomic utilization. However, conventional synthesis of SA-M catalysts involves high-temperature treatments, leading to a low yield with random distribution of atoms. Herein, a facile method to synthesize SA-M catalysts (M = Fe, Ir, Pt, Ru, Cu, or Pd) in a single step at ambient temperature, using the extracellular electron transfer capability of Geobacter sulfurreducens (GS), is presented. Interestingly, the SA-M is coordinated to three nitrogen (N) atoms adopting an MN3 on the surface of GS. Dry samples of SA-Ir@GS without further heat treatments show exceptionally high activity for OER when compared to benchmark IrO2 catalyst and comparable HER activity to commercial 10 wt.% Pt/C. The SA-Ir@GS electrocatalyst exhibits the best water‐splitting performance compared to other SA-M@GS, showing a low applied potential of 1.65 V to achieve 10 mA cm−2 in 1.0 M KOH solution with cycling over 5 h. The density functional calculations reveal that the large adsorption energy of H2O and moderate adsorption energies of reactants and reaction intermediates for SA-Ir@GS favorably improve its activity. This nature-based facile synthesis method of SA-M at room temperature provides a versatile platform for the preparation of other transition metal SA-M catalysts for various energy-related applications by merely altering the metal precursors.