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 materials' parameter(s) that modulate hydrogen-material interaction. In a recent publication, we have shown that the reduction (de-nitridation) 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 content 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 (de-oxidation) in H*. This leads to the stabilization of the higher oxidation states of a high work function TM, which otherwise readily reduce in H*. We propose that the work function serves as a tuneable parameter, modulating the interaction of hydrogen with TM compounds.