Photoelectrochemical (PEC) water splitting is a highly promising approach for sustainable hydrogen production. BiVO₄ (BVO) possesses an appropriate bandgap and excellent optical properties; however, its poor carrier transport and sluggish water-oxidation kinetics severely limit the utilization of holes, leading to low PEC efficiency. Herein, we rationally design a p–n heterojunction with a stepwise type-II energy band configuration through the in-situ growth of p-type FeCoMOF on n-type BVO. This architecture promotes the efficient and selective separation of photogenerated electrons and holes, enabling the BVO/FeCoMOF photoanode to achieve enhanced PEC water oxidation performance. The optimized photoanode delivers a remarkable photocurrent density of 6.2 mA·cm⁻² at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination, which is 3.8 times higher than that of bare BVO photoanode, and exhibits significantly enhanced operational stability compared to the bare BVO. Furthermore, gas-evolution tests confirm highly stoichiometric water splitting, yielding an H₂/O₂ ratio close to 2:1, along with a Faradaic efficiency exceeding 92%. Detailed physicochemical characterization, including intensity-modulated photocurrent spectroscopy (IMPS), intensity-modulated photovoltage spectroscopy (IMVS), and in-situ Kelvin probe force microscopy (KPFM), confirm that the construction of the type-II p–n heterojunction effectively promotes the hole transfer from BVO to the FeCoMOF layer, enhances the charge-separation efficiency, and prolongs the carrier lifetime. Furthermore, the FeCoMOF modification significantly reduces the interfacial reaction resistance and enhances the charge utilization efficiency, thereby further improving the PEC performance. This work provides new insights into the rational design of high-performance photoelectrode.

Replacing the challenging water oxidation with thermodynamically favorable organic oxidation presents a promising strategy for the efficient simultaneous production of hydrogen and value-added chemicals. However, photocatalytic activity is hindered by inefficient separation of photogenerated electron–hole pairs and limited redox active sites. Herein, Fe/ZnIn₂S₄/Ni (Fe/ZIS/Ni) micro heterojunctions were rationally engineered for synergistically photocatalytic hydrogen evolution and selective oxidation of benzylamine. Using Fe-based metal–organic frameworks (MIL-88A) as the self-etching morphology template and iron source, ZIS was grown in situ to obtain Fe-doped ZIS (Fe/ZIS). Then nickel was introduced into Fe/ZIS to locally construct Ni-doped ZIS (ZIS/Ni) microregion, thereby forming numerous microscopic heterojunctions (Fe/ZIS/Ni). The introduction of Fe effectively lowers the energy band (EB) position of Fe/ZIS, while the introduction of Ni elevates the EB position of ZIS/Ni microregion. Such difference in the EB structures of Fe/ZIS and ZIS/Ni promote the formation of local electric field, effectively suppresses the recombination of photogenerated carriers and enhances their efficient separation and migration. Moreover, the nanosheet assembly structure increases the availability of active sites and enhances the uptake of reactants. The optimized Fe/ZIS/Ni catalyst achieves remarkable hydrogen evolution and N-benzylidenebenzylamine (NBI) production rates of 7.9 and 6.8 mmol·g⁻¹·h⁻¹, respectively. Additionally, the selectivity for the oxidation of benzylamine to NBI exceeds 95%. This work establishes a novel design paradigm for developing high-performance photocatalytic systems that integrate renewable H₂ production with selective organic transformations.

Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-value-added chemicals, but it is hampered by sluggish charge dynamics and limited redox potential. Herein, a porous S-doped carbon nitride (S-C₃N_4−y) foam assembled from ultrathin nanosheets with rich nitrogen vacancies was synthesized using a molecular self-assembly strategy. The S dopants and N vacancies synergistically adjusted the band structure, facilitating light absorption and enhancing the oxidation ability. Moreover, the ultrathin nanosheets and porous structure provided more exposed active sites and facilitated mass and charge transfer. Consequently, S-C₃N_4−y foam exhibited enhanced photocatalytic activities for synchronous hydrogen evolution (4960 μmol/(h·g)) and benzylamine oxidation to N-benzylidenebenzylamine (4885 μmol/(h·g)) with high selectivity of > 99 %, which were approximately 17.6 and 72.9 times higher than those of bulk CN, respectively. The photocatalytic coupling pairing reaction promotes the water splitting by consuming H₂O₂, thereby improving the hydrogen evolution efficiency and achieving the production of high value-added imines. This study provides an effective route for regulating the morphology and band structure of carbon nitride for synthesizing highly valuable chemicals.

The development of highly active and stable acidic water oxidation electrocatalysts is of great significant for promoting the industrial application of proton exchange membrane electrolyzers. Ru-based catalysts have broad application prospects in acidic water oxidation, but their limitations in stability and activity hinder their further application. Herein, a nitrogen-doped carbon (NC) coated porous Ru/RuO₂ heterojunctional hollow sphere (Ru/RuO₂/NC) is designed as high-active and stable bifunctional electrocatalyst for acidic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In synthesis, the key is to use mesoporous polydopamine spheres as a template for forming hollow spheres, a source of NC coating and a reducing agent for forming Ru/RuO₂ heterojunction. The Ru/RuO₂ heterojunction adjusts the electronic structure of Ru active sites, optimizing the adsorption of intermediate species. Furthermore, the NC coating and the interaction between NC and Ru/RuO₂ effectively prevent Ru from over-oxidation and dissolution. The porous hollow structure provides more exposed active sites and promotes mass transfer. Impressively, Ru/RuO₂/NC exhibits outstanding OER and HER performance with low overpotentials of 211 and 32 mV at 10 mA·cm⁻², respectively, and shows excellent stability. The acid water splitting electrolyzer, based on the bifunctional Ru/RuO₂/NC, requires low cell voltages of 1.46 and 1.76 V at 10 and 100 mA·cm⁻², respectively, with good stability for over 100 h operation, surpassing Pt/C||RuO₂ and most of the reported catalysts.