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Multifunctional catalysts that integrate high efficiency hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalytic activity in a single material are attractive for unitized regenerative fuel cells and overall water splitting technologies. As the best-known HER and ORR electrocatalysts, Pt and its alloys have only moderate OER activity. Ruthenium and iridium oxides exhibit the highest OER activities but not as active as Pt for HER and ORR. Here, we proposed a general principle for achieving trifunctional electrocatalysis for three reactions in a single material. Using the newly-synthesized pyrazine-modified graphdiyne (PR-GDY) as an example, we demonstrated that the synergistic effect of the pyridinic nitrogen and anchored transition-metal (TM) single atoms renders highly-efficient HER/OER/ORR trifunctional electrocatalytic activity. For the Ni-doped PR-GDY, the overpotentials for HER, OER and ORR can be respectively as low as −0.05, 0.29 and 0.38 V, which are comparable or even superior to the best-known single-functional and bi-functional precious electrocatalysts. These computational results offer not only a promising trifunctional electrocatalyst but also a strategy for the design of multifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transition-metal atoms can be firmly anchored on pyGY monolayer without clustering. • Co@pyGY and Pt@pyGY are efficient catalysts for HER/OER and OER/ORR, respectively. • Ni@pyGY and Pd@pyGY can serve as promising trifunctional SACs for HER/OER/ORR. • The tunable catalytic activity of TM-N 2 unit sheds light on electrocatalysts design. Highly efficient single-atom catalysts (SACs) with maximal utility rate of metal atoms hold great promise in the energy storage devices. Support materials which can not only firmly anchor the active metal atoms but also modulate the catalytic activity are crucial for SACs. Here, we demonstrate from first-principles that the unique pores of pyrazine-modified graphyne (pyGY) which has been synthesized in recent experiments are quite promising for anchoring transition-metal (TM) atoms to achieve SACs due to the TM-N 2 units. Among the ten TM@pyGYs, we filtered out two bifunctional SACs, Co@pyGY and Pt@pyGY, as efficient water splitting (HER/OER) and metal-air battery (OER/ORR) catalysts, respectively. More interestingly, Ni@pyGY and Pd@pyGY can act as efficient HER/OER/ORR trifunctional electrocatalysts. These multifunctional catalysts have the overpotentials comparable or superior to those of the conventional unifunctional catalysts. This work provides a new group of promising multifunctional SACs, as well as a useful guidance for electrocatalyst design. [ABSTRACT FROM AUTHOR]

• We demonstrated the Fe-PTC monolayer can serve as a trifunctional electrocatalyst. • Fe-PTC has high electrocatalytic activity for HER with overpotential is −0.23 V. • The p-band center as descriptor is used to reveal the origins of catalytic activity. • Fe-PTC is a potential electrocatalyst for both OER and ORR with low overpotentials. Integrating high efficiency hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in multifunctional electrocatalysts is attractive for the unitized regenerative fuel cells and overall water splitting technologies. We demonstrated from first-principles calculations the recently- synthesized two-dimensional (2D) metal-organic frameworks (MOFs), namely transition metal 1,2,3,4,5,6,7,8,9,10,11,12- perthiolated coronene (TM-PTC) have multifunctional electrocatalytic activity for HER, OER and ORR. In particular, Fe-PTC monolayer can serve as a trifunctional electrocatalyst for overall water splitting and rechargeable metal-air battery with low overpotentials comparable to those of the well-developed unifunctional electrocatalysts. The origins of the trifunctional electrocatalytic activity were also discussed. This work is expected to open an avenue for the design of highly-efficient multifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reaction (HER) plays an important role in water splitting to produce hydrogen. The high price of precious platinum-based catalysts that are the best HER electrocatalysts by now hampers the commercial application. Low-cost, earth-abundant and highly-efficient HER electrocatalysts are thus long-desired. On the basis of first-principles calculations, we investigated the HER electrocatalytic performance of the non-precious TiF 3 and its analogs. Our calculations showed that TiF 3 and WO 3 can serve as efficient HER electrocatalysts with the overpotentials comparable to those of the platinum-based catalysts. To uncover the origins of electrocatalytic performance, we established a relationship between the surface adsorption ability of a material and its electronic structure. The low HER overpotentials, unique porous structure and high abundance in earth make these materials promising candidates for high-performance HER electrocatalysts. Unlabelled Image • We proposed a new family of electrocatalytic materials with intrinsic porous structures - TiF 3 and its analogs. • Non-precious TiF 3 (ΔG H⁎ = -0.03 eV) and its analog WO 3 (ΔG H⁎ = -0.05 eV) can serve as efficient HER electrocatalysts. • A descriptor based on the d-band center is proposed to reveal the origins of catalytic activity. • The low overpotential and unique porous structure make them promising candidates for HER electrocatalysts [ABSTRACT FROM AUTHOR]