Plasma-assisted fabrication of ultra-dispersed copper oxides in and on C-rich carbon nitride as functional composites for the oxygen evolution reaction.

Significant efforts have been continuously devoted to the mastering of green catalysts for the oxygen evolution reaction (OER), whose sluggish kinetics prevents a broad market penetration of water splitting as a sustainable route for large-scale hydrogen production. In this extensive scenario, carbon nitride (CN)-based systems are in focus thanks to their favorable characteristics, and, whereas graphitic CN has been largely investigated, the potential of amorphous carbon nitride (a-CN x ) systems remains almost entirely unexplored. In this regard, our study presents a novel two-step plasma-assisted route to a-CN x systems comprising ultra-dispersed, i.e. "quasi-atomic" Cu x O ( x = 1, 2). The target materials were fabricated using an original strategy consisting in the magnetron sputtering of a-CN x on conducting glasses at room temperature, followed by functionalization with low Cu x O amounts by radio frequency (RF)-sputtering, and final annealing under an inert atmosphere. The tailoring of the Cu x O co-catalyst content and spatial dispersion, as well as the overall composite features as a function of preparative conditions, enabled a direct modulation of the resulting OER performances, rationalized based on the formation of p-n Cu x O/a-CN x heterojunctions. The amenable and scalable synthesis approach underscores the practicality of this method to develop (photo)electrocatalysts synergistically integrating the advantages of both constituents, yielding low-cost, green, and stable functional platforms that could contribute to the broader adoption of sustainable energy solutions.