Oxygen-tolerant proton reduction catalysis: much O2 about nothing?

Proton reduction catalysts are an integral component of artificial photosynthetic systems for the production of H2. This perspective covers such catalysts with respect to their tolerance towards the potential catalyst inhibitor O2. O2 is abundant in our atmosphere and generated as a by-product during the water splitting process, therefore maintaining proton reduction activity in the presence of O2 is important for the widespread production of H2. This perspective article summarises viable strategies for avoiding the adverse effects of aerobic environments to encourage their adoption and improvement in future research. H2-evolving enzymatic systems, molecular synthetic catalysts and catalytic surfaces are discussed with respect to their interaction with O2 and analytical techniques through which O2-tolerant catalysts can be studied are described.