The future of energy supply depends on innovative breakthroughs in the development of highly efficient, sustainable and low-cost systems for renewable energy conversion and storage. Water splitting is a promising and appealing solution. In this work, we report Co(OH)2 on the carbon nanotube/polyimide film (PI/CNT-Co(OH)2) as an efficient electrocatalyst for the oxygen evolution reaction (OER). The PI/CNT film allows intimate growth of Co(OH)2 nanosheets on its surface. The nanosheet structure of Co(OH)2 and the underlying PI/CNT film facilitate the good OER performance of the PI/CNT-Co(OH)2 film. Co(OH)2 nanosheets on the PI/CNT film afford an earlier onset of oxygen evolution, a low overpotential of 317 mV and a small Tafel slope of 49 mV per decade in alkaline media. This work applies the PI/CNT film in water splitting to enhance the OER electrocatalytic activity of Co(OH)2, which opens up a promising avenue for the exploration of highly active electrocatalysts that can replace noble-metal based catalysts for the OER.

This work shows a novel artificial Z‐scheme photosystem based on a heterometallic Zn‐/Pt‐porphyrin conjugated polymer (ZnPtP‐CP) grafted onto ultrathin BiVO4 nanosheets via Zn–O–V bridging bonds for high‐efficiency overall water photosplitting. An impressive apparent quantum yield of 9.85% at λ = 400 nm is achieved over the resulting ZnPtP–CP/BiVO4 composite, in which BiVO4 nanosheets are in close contact with ZnPtP‐CP nanosheets via Zn–O–V bridging bonds to promote a Z‐scheme charge transfer mechanism with ZnPtP‐CP serving as electron‐rich unit and BiVO4 as hole‐rich one. The photoexcited electrons of BiVO4 transfer to the interface and recombine with the photogenerated holes of ZnPtP‐CP through the Zn–O–V bonds, and thus the strong reducibility of the photoinduced electrons in ZnPtP‐CP and the strong oxidation ability of the photogenerated holes in BiVO4 are maintained. Moreover, the highly dispersed Pt centers (PtN4) in Pt‐porphyrin bridging units act as single‐atom catalytic sites to facilitate a cascade charge transfer by fast migration of the photogenerated electrons from Zn‐porphyrin to Pt‐porphyrin units for the water reduction reaction. This Z‐scheme mechanism with two‐step excitation and cascade charge transfer pathway makes the composite acting as Z‐scheme dual‐function photocatalyst responsible for the efficient solar‐driven overall water photosplitting without the aid of a sacrificial reagent or external bias.

A novel heterometallic Zn‐/Co‐porphyrin conjugated polymer (ZnCoP‐F CP) with its Co‐porphyrin bridging unit bearing two perfluorophenyls is synthesized via a Sonogashira coupling reaction. The resulting ZnCoP‐F CP without the Pt cocatalyst exhibits broadband (UV–vis–NIR) light‐driven hydrogen evolution activity of 83 µmol h−1, which is more than twice that (39 µmol h−1) of its counterpart (ZnCoP CP) with the Co‐porphyrin unit bearing two phenyls. Furthermore, an apparent quantum yield of 6.92%, 5.50%, 5.78%, 3.17%, and 0.73% is achieved from the ZnCoP‐F CP illuminated at 400, 500, 550, 700, and 850 nm monochromatic light, respectively. The enhanced performance of ZnCoP‐F CP can be attributed to the high electron‐withdrawing capacity of its perfluorophenyls and the highly dispersed Co centers in Co‐porphyrin bridging units serving as single‐atom catalytic sites (CoN4), which facilitate the formation of periodic type II‐like heterojunctions and the fast charge transfer from Zn‐porphyrin to Co‐porphyrin units for hydrogen evolution reaction. The broadband‐responsive feature is due to the large π‐conjugated system through the whole 2D internal framework of the porphyrin polymer. This work opens a new path to fabricate porphyrin‐based polymer with an efficient and broadband‐responsive hydrogen evolution system.

In order to explore a new electrocatalyst (or its precursor) for oxygen evolution reaction (OER), much attention has recently been given to the alternative engineering strategy for fabricating a novel nanofilm electrode with high efficiency and long duration. We herein use a two-step electrodeposition method to prepare a series of nanofilm electrodes containing Ni, Co, P, and Se on carbon cloth. After a suitable electrochemical activation process through cyclic voltammetry, the resultant binder-free NiCoP−NiCoSe 2 nano-bilayer films are transformed from compact layer(s) to porous nanoparticle ones composed by NiCo hydroxides and a small amount of NiCo oxyhydroxides and thus exhibit a striking electrocatalytic activity (lower to 243 mV overpotential for 10 mA cm −2 ) and excellent stability (80 h) for OER. The rougher surface, well-suited electronic structure originated from the Ni/Co codoping and the rational integration of NiCoP and NiCoSe 2 are important factors for the excellent OER performance of the NiCoP−NiCoSe 2 film after the electrochemical activation process. In addition, the results on overall water splitting reveal that the NiCoP−NiCoSe 2 film is also promising in the practical application of energy conversion and storage.

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Organic polymers have attracted much attention in the field of energy conversion owing to their excellent tailoring ability via heterometal incorporation and/or functionalization. Herein, a novel pincer complexbridged porphyrin polymer is synthesized using Cu-porphyrin (CuPor) and Ru-N′NN′-pincer complex (RuN 3 ) as monomers. The resultant CuPor-RuN 3 polymer delivers robust electrocatalytic hydrogen evolution reaction (HER) performance with outstanding durability and ultralow overpotentials of 73 and 114 mV at a current density of 10 mA cm -2 in acidic and alkaline media, respectively. Moreover, the CuPor-RuN 3 polymer displays great potential to fabricate photoelectrochemical (PEC) cells with a BiVO 4 photoanode, where the additional photoinduced electrons from CuPor-RuN 3 endow the BiVO 4 ||CuPor-RuN 3 PEC cell with much better activity for overall water splitting than the BiVO 4 ||Pt/C one, demonstrating that CuPor-RuN 3 would be a promising (photo)electrocatalyst to replace the benchmark Pt/C. The experimental and theoretical studies reveal that the Cu/Ru heterobimetallic centers in the polymer not only enhance the inherent electron transfer from Cu sites to Ru ones that serve as singleatom catalytic sites (Ru-N 3 ), but also efficiently regulate the electronic property of the Ru-N 3 sites, and thus boosting (photo)electrocatalytic HER activity. The proposed strategy opens a new avenue to fabricate porphyrinbased polymers with heteromultimetallic centers as effective HER (photo)electrocatalysts.

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