Formic acid (HCOOH) is one of the most promising chemical fuels that can be produced through CO 2 electroreduction. However, most of the catalysts for CO 2 electroreduction to HCOOH in aqueous solution often suffer from low current density and limited production rate. Herein, we provide a bismuth/cerium oxide (Bi/CeO x) catalyst, which exhibits not only high current density (149 mA cm À2), but also unprecedented production rate (2600 mmol h À1 cm À2) with high Faradaic efficiency (FE, 92 %) for HCOOH generation in aqueous media. Furthermore, Bi/CeO x also shows favorable stability over 34 h. We hope this work could offer an attractive and promising strategy to develop efficient catalysts for CO 2 electroreduction with superior activity and desirable stability. Excessive CO 2 emission has brought about severe problems related to resources, environment, and climate. Thus, converting CO 2 into valuable chemical fuels attract more and more research attention. [1] Among the various conversion approaches, electrochemical reduction of CO 2 in aqueous media is more favorable because it can make better use of electricity generated from sustainable sources without producing any additional CO 2. [1-5] Nevertheless, low activity, selectivity and stability of catalysts are still the big challenges for CO 2 electroreduction. Therefore, developing efficient electrocatalysts for CO 2 reduction is highly desired. As one of the most attractive CO 2 reduction products, formic acid (HCOOH) is widely identified as a desirable hydrogen carrier. [6-10] Up to now, many metallic catalysts, including Cd, Hg, Pd, Pb, In, Sn and Bi are found to be effective to form HCOOH (or formate) through CO 2 electroreduction. [11-29] However, the activities are still very low even using the toxic or noble metals. As well as we know, the current density and production rate (in H-type reaction cell) by far are less than 80 mA cm À2 , and 1500 mmol h À1 cm À2 , respectively. [11-29] On the other side, high applied potentials and current density always lead to the low Faradaic efficiency (FE) due to the severe competitive hydrogen evolution reaction (HER). [25] Therefore, achieving a low-cost, eco

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Efficient and selective dehydrogenation of formic acid is a key challenge for a fuel‐cell‐based hydrogen economy. Though the development of heterogeneous catalysts has received much progress, their catalytic activity remains insufficient. Moreover, the design principle of such catalysts are still unclear. Here, experimental and theoretical studies on a series of mono‐/bi‐metallic nanoparticles supported on a NH2‐N‐rGO substrate are combined for formic acid dehydrogenation where the surface energy of a metal is taken as a relevant indicator for the adsorption ability of the catalyst for guiding catalyst design. The AuPd/NH2‐N‐rGO catalyst shows record catalytic activity by reducing the energy barrier of rate controlling steps of formate adsorption and hydrogen desorption. The obtained excellent results both in experiments and simulations could be extended to other important systems, providing a general guideline to design more efficient catalysts.

Highlights A novel physical approach is proposed to enhance the electrocatalytic performance by electric field. Under the action of electric field, some stable conductive filaments consisting of oxygen vacancies are formed in the Ni/Co 3 O 4 film, which remarkably reduces the system resistivity. The electric-field-treated Ni/Co 3 O 4 material exhibits significantly superior activity and stability as a bifunctional electrocatalyst for overall water splitting, and its performance exceeds the state-of-the-art electrocatalysts. Abstract Rational design of bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with excellent activity and stability is of great significance, since overall water splitting is a promising technology for sustainable conversion of clean energy. However, most electrocatalysts do not simultaneously possess optimal HER/OER activities and their electrical conductivities are intrinsically low, which limit the development of overall water splitting. In this paper, a strategy of electric field treatment is proposed and applied to Ni/Co 3 O 4 film to develop a novel bifunctional electrocatalyst. After treated by electric field, the conductive channels consisting of oxygen vacancies are formed in the Co 3 O 4 film, which remarkably reduces the resistance of the system by almost 2 × 10 4 times. Meanwhile, the surface Ni metal electrode is partially oxidized to nickel oxide, which enhances the catalytic activity. The electric-field-treated Ni/Co 3 O 4 material exhibits super outstanding performance of HER, OER, and overall water splitting, and the catalytic activity is significantly superior to the state-of-the-art noble metal catalysts (Pt/C, RuO 2 , and RuO 2 ǁ Pt/C couple). This work provides an effective and feasible method for the development of novel and efficient bifunctional electrocatalyst, which is also promising for wide use in the field of catalysis. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-022-00889-3.