Role of Active Centers in Predicting the Catalyst Turnover: A Theoretical Study

Water oxidation catalysis has garnered significant attention due to its potential for sustainable energy conversion. Among molecular catalysts, [Fe(OTf)₂( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msup><mml:mrow></mml:mrow> <mml:msub><mml:mi>Me</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:msup> <mml:annotation>${^{{\rm{Me}}_{\rm{2}} } }$</mml:annotation> </mml:semantics> </mml:math> Pytacn)] complexes have exhibited notable turning-over rates. Although various [M(OTf)₂( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msup><mml:mrow></mml:mrow> <mml:msub><mml:mi>Me</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:msup> <mml:annotation>${^{{\rm{Me}}_{\rm{2}} } }$</mml:annotation> </mml:semantics> </mml:math> Pytacn)] complexes (M=Mn, Co, Ni) have been synthesized, however, the role of active centres has not been thoroughly investigated. In this study, we apply our newly developed catalytic models, efficiency conceptualization model (ECM) and the maximum kinetic efficiency MaxKinEff framework to assess the role of the active centres in its catalytic performance. Our computational analysis identifies cobalt-based [Co(OTf)₂( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msup><mml:mrow></mml:mrow> <mml:msub><mml:mi>Me</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:msup> <mml:annotation>${^{{\rm{Me}}_{\rm{2}} } }$</mml:annotation> </mml:semantics> </mml:math> Pytacn)] as a superior alternative for water oxidation reactions. Notably, cobalt catalysts exhibit a longer lifespan (∼44 days) and higher turnover numbers (TON), with computed values of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>Γ</mml:mi> <mml:mrow><mml:mi>c</mml:mi> <mml:mi>o</mml:mi> <mml:mi>m</mml:mi> <mml:mi>p</mml:mi> <mml:mi>u</mml:mi> <mml:mi>t</mml:mi> <mml:mi>e</mml:mi> <mml:mi>d</mml:mi> <mml:mspace></mml:mspace> <mml:mi>T</mml:mi> <mml:mi>O</mml:mi> <mml:mi>F</mml:mi></mml:mrow> <mml:mn>0</mml:mn></mml:msubsup> <mml:annotation>${{\rm{\Gamma }}_{computed\;TOF}^0 }$</mml:annotation> </mml:semantics> </mml:math> (ECM)=3.30 h^-1, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>τ</mml:mi> <mml:mrow><mml:mi>c</mml:mi> <mml:mi>o</mml:mi> <mml:mi>m</mml:mi> <mml:mi>p</mml:mi> <mml:mi>u</mml:mi> <mml:mi>t</mml:mi> <mml:mi>e</mml:mi> <mml:mi>d</mml:mi> <mml:mspace></mml:mspace> <mml:mi>T</mml:mi> <mml:mi>O</mml:mi> <mml:mi>N</mml:mi></mml:mrow> <mml:mn>0</mml:mn></mml:msubsup> <mml:annotation>${\tau _{computed\;TON}^0 }$</mml:annotation> </mml:semantics> </mml:math> (ECM)=3456, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>Γ</mml:mi> <mml:mrow><mml:mi>m</mml:mi> <mml:mi>a</mml:mi> <mml:mi>x</mml:mi> <mml:mspace></mml:mspace> <mml:mi>T</mml:mi> <mml:mi>O</mml:mi> <mml:mi>F</mml:mi></mml:mrow> <mml:mn>0</mml:mn></mml:msubsup> <mml:annotation>${{\rm{\Gamma }}_{max\;TOF}^0 }$</mml:annotation> </mml:semantics> </mml:math> (MaxKinEff)=12.43 h^-1, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>τ</mml:mi> <mml:mrow><mml:mi>m</mml:mi> <mml:mi>a</mml:mi> <mml:mi>x</mml:mi> <mml:mspace></mml:mspace> <mml:mi>T</mml:mi> <mml:mi>O</mml:mi> <mml:mi>N</mml:mi></mml:mrow> <mml:mn>0</mml:mn></mml:msubsup> <mml:annotation>${\tau _{max\;TON}^0 }$</mml:annotation> </mml:semantics> </mml:math> (MaxKinEff)=3616. These findings suggest that cobalt could play a pivotal role in improving the efficiency of molecular catalysts for water oxidation.