Engineering Work Function to Stabilize Metal Oxides in Reactive Hydrogen

Hydrogen, crucial for the green energy transition, poses a challenge due to its tendency to degrade surrounding wall materials. To harness hydrogen's potential, it is essential to identify the parameter(s) of materials that modulates hydrogen-material interaction. In a recent publication, we have shown that the reduction (denitridation) of transition metal (TM) nitrides in hydrogen radicals (H*) stops when their work function drops below a threshold limit. In this work, we tailor the work function of a complex TM oxide by tuning the relative contents of its constituent TM atoms. We show that increasing the fraction of a low-work function TM decreases the work function of the complex oxide, thereby decreasing its reducibility (deoxidation) in H*. This leads to the stabilization of the higher oxidation states of a high-work function TM, which otherwise would be readily reduced in H*. We propose that the work function serves as a tunable parameter, modulating the interaction of hydrogen with TM compounds.