Boron-doped graphene with different boron structures was rationally synthesized to enhance the adsorption of N 2 , thus enabling an efficient metal-free electrocatalyst for electrochemical N 2 reduction in aqueous solution at ambient conditions. At a doping level of 6.2%, boron-doped graphene achieved a NH 3 production rate of 9.8 mg$hr À1 $cm À2 and an excellent faradic efficiency (10.8% at À0.5 V versus reversible hydrogen electrode).

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The electrocatalytic reduction of CO2 into value-added chemicals such as hydrocarbons has the potential for supplying fuel energy and reducing environmental hazards, while the accurate tuning of electrocatalysts at the ultimate single-atomic level remains extremely challenging. In this work, we demonstrate an atomic design of multiple oxygen vacancy-bound, single-atomic Cu-substituted CeO2 to optimize the CO2 electrocatalytic reduction to CH4. We carried out theoretical calculations to predict that the single-atomic Cu substitution in CeO2(110) surface can stably enrich up to three oxygen vacancies around each Cu site, yielding a highly effective catalytic center for CO2 adsorption and activation. This theoretical prediction is consistent with our controlled synthesis of the Cu-doped, mesoporous CeO2 nanorods. Structural characterizations indicate that the low concentration (<5%) Cu species in CeO2 nanorods are highly dispersed at single-atomic level with an unconventionally low coordination number ∼5, suggesting the direct association of 3 oxygen vacancies with each Cu ion on surfaces. This multiple oxygen vacancy-bound, single atomic Cu-substituted CeO2 enables an excellent electrocatalytic selectivity in reducing CO2 to methane with a faradaic efficiency as high as 58%, suggesting strong capabilities of rational design of electrocatalyst active centers for boosting activity and selectivity.