Copper oxide-based materials effectively electrocatalyze carbon dioxide reduction (CO 2 RR). To comprehend their role and achieve high CO 2 RR activity, Cu + in copper oxides must be stabilized. As an electrocatalyst, Cu 2 O nanoparticles were decorated with hexagonal boron nitride (h-BN) nanosheets to stabilize Cu + . The C 2 H 4 /CO ratio increased 1.62-fold in the CO 2 RR with Cu 2 OÀ BN compared to that with Cu 2 O. Experimental and theoretical studies confirmed strong electronic interactions between the two components in Cu 2 OÀ BN, which strengthens the CuÀ O bonds. Electrophilic h-BN receives partial electron density from Cu 2 O, protecting the CuÀ O bonds from electron attack during the CO 2 RR and stabilizing the Cu + species during longterm electrolysis. The well-retained Cu + species enhanced the C 2 product selectivity and improved the stability of Cu 2 OÀ BN. This work offers new insight into the metal-valence-state-dependent selectivity of catalysts, enabling the design of advanced catalysts.

Efficient conversion of carbon dioxide (CO 2 ) into value-added materials and feedstocks, powered by renewable electricity, presents a promising strategy to reduce greenhouse gas emissions and close the anthropogenic carbon loop. Recently, there has been intense interest in Cu 2 O-based catalysts for the CO 2 reduction reaction (CO 2 RR), owing to their capabilities in enhancing C−C coupling. However, the electrochemical instability of Cu + in Cu 2 O leads to its inevitable reduction to Cu 0 , resulting in poor selectivity for C 2+ products. Herein, we propose an unconventional and feasible strategy for stabilizing Cu + through the construction of a Ce 4+ 4f−O 2p− Cu + 3d network structure in Ce-Cu 2 O. Experimental results and theoretical calculations confirm that the unconventional orbital hybridization near E f based on the high-order Ce 4+ 4f and 2p can more effectively inhibit the leaching of lattice oxygen, thereby stabilizing Cu + in Ce-Cu 2 O, compared with traditional d−p hybridization. Compared to pure Cu 2 O, the Ce-Cu 2 O catalyst increased the ratio of C 2 H 4 /CO by 1.69-fold during the CO 2 RR at −1.3 V. Furthermore, in situ and ex situ spectroscopic techniques were utilized to track the oxidation valency of copper under CO 2 RR conditions with time resolution, identifying the well-maintained Cu + species in the Ce-Cu 2 O catalyst. This work not only presents an avenue to CO 2 RR catalyst design involving the high-order 4f and 2p orbital hybridization but also provides deep insights into the metal-oxidation-statedependent selectivity of catalysts.

The development of highly selective and efficient catalysts for the electrochemical reduction of CO2 (CO2RR) to value-added chemical products is a promising pathway towards zero emissions and carbon neutrality. Cu2O...

Copper oxide-based materials effectively electrocatalyze carbon dioxide reduction (CO 2 RR). To comprehend their role and achieve high CO 2 RR activity, Cu + in copper oxides must be stabilized. As an electrocatalyst, Cu 2 O nanoparticles were decorated with hexagonal boron nitride (h-BN) nanosheets to stabilize Cu + . The C 2 H 4 /CO ratio increased 1.62-fold in the CO 2 RR with Cu 2 OÀ BN compared to that with Cu 2 O. Experimental and theoretical studies confirmed strong electronic interactions between the two components in Cu 2 OÀ BN, which strengthens the CuÀ O bonds. Electrophilic h-BN receives partial electron density from Cu 2 O, protecting the CuÀ O bonds from electron attack during the CO 2 RR and stabilizing the Cu + species during longterm electrolysis. The well-retained Cu + species enhanced the C 2 product selectivity and improved the stability of Cu 2 OÀ BN. This work offers new insight into the metal-valence-state-dependent selectivity of catalysts, enabling the design of advanced catalysts.

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