A unique Bi2O2CO3/CeO2 heterostructure in-situ derived from BiCeOx nanorods for efficient CO2 electroreduction within ultra-broad potential windows

The electroreduction of CO 2 to value-added chemicals is a lucrative route to simultaneously achieve renewable energy conversion and mitigate the greenhouse effect. Herein, an in-situ derived Bi 2 O 2 CO 3 /CeO 2 heterostructure is exquisitely constructed, which can produce formate with the faradaic efficiency of 98.6 % in ultra-broad potential windows of 3000 mV, and directly generate pure formic acid with the highest selectivity of 95.2 % and the maximal energy efficiency of 53.9 % in the neutral solid-electrolyte cell, surpassing most of the reported results and demonstrating the potential for future industrialization. The experimental and theoretical results indicate that the CeO 2 with abundant oxygen vacancies is conducive to facilitating the dissociation of water, serving as the source of active hydrogen species in the heterostructure. The Bi 2 O 2 CO 3 is used to effectively activate CO 2 and fast hydrogenate the crucial *OCHO-to-*OCHOH step accelerated by adequate supply of active hydrogen species. Thus, the heterostructure synergistically promotes the efficient conversion of CO 2 to cost-effective formic acid/formate products. As a result, this work provides a fundamental understanding and detailed exposition of Bi-based catalysts for highly selective CO 2 reduction and offers a unique but universal strategy for rational design and in-situ synthesis of heterostructure materials in various fields of energy storage and conversion.