Metal-organic frameworks stabilized Mo and W binary single-atom catalysts as high performance bifunctional electrocatalysts for water electrolysis

Single atom catalysts (SACs) are commonly composed of single atoms (SAs) anchored on relatively inert supports containing surface heteroatoms, leading to low specific catalytic efficiency. A new SAC design strategy, anchoring SAs on catalytically active porous supports, was proposed and demonstrated with NiFe-based metalorganic frameworks (MOFs) stabilized Mo and W binary SACs, MOF-MoSAWSA, as highly efficient and stable bifunctional electrocatalysts for electrolytic water splitting. MOF-MoSAWSA delivered current densities of 10 and 500 mA cm-2 at ultralow overpotentials of 199 and 250 mV for oxygen evolution reaction and at decent overpotentials of 57 and 297 mV for hydrogen evolution reaction, respectively. For overall water splitting, the MOF-MoSAWSA//MOF-MoSAWSA couple achieved ultralow cell voltages of 1.501 and 1.780 V to deliver current densities of 10 and 500 mA cm-2, respectively, and exhibited excellent stability with only 2% decay in current densities after a 56-hour operation at an ultrahigh initial current density of 515 mA cm-2. The success was attributed to the positive synergy between the SAs and MOF and between Mo and W SAs, as revealed with X-ray absorption and photoelectron spectroscopic analyses. The present development offers a new route for fabrication of advanced SA based catalysts.