Construction of shell-core Co2P/Cd0.9Zn0.1S photocatalyst by electrostatic attraction for enhancing H2 evolution

Improving insight into the localized electrochemical Volmer reaction based on surface enhanced Raman spectroscopy and collisions

An operando EC-SERS strategy was successfully developed for monitoring the Volmer reaction based on dynamic collisions. Its feasibility and universality were verified, and it provided a promising approach for visualizing a localized surface reaction.

Design of p-n heterojunction between CoWO4 and Zn-defective Zn0.3Cd0.7S for efficient photocatalytic H2 evolution

To enhance the efficiency of photocatalytic H2 evolution, numerous methods are employed by increasing the utilization of photogenerated charge carriers (PCCs), including catalyst design, defect regulation, and selection of suitable H+ resources. Using self-assembly method, CoWO4/ZnxCd1-xS with p-n heterojunction was synthesized. Although CoWO4 (CW) cannot produce H2 under visible light irradiation, it can provide photogenerated electrons (e-) to Zn0.3Cd0.7S (ZCS), and largely increase the photocatalytic activity of ZCS. The optimal CW/ZCS composite can reach 15.58 mmol·g-1·h-1, which is 45.8 and 24.3 times higher than the values of the pure CdS and ZCS, respectively. The largely enhanced photocatalytic H2 production is attributed to the Zn vacancies (VZn), p-n heterojunction, and p-chlorobenzyl alcohol (Cl-PhCH2OH) as the H+ source of H2 production. VZn on the ZCS surface as the capture center of photogenerated holes (h+), can regulate the carrier distribution, which results in more photogenerated e- and less generated h+. The combination of p-n heterojunction and VZn can enhance the separation and transfer efficiency of PCCs, and effectively inhibit the recombination of charge carriers. To further improve the utilization rate of PCCs, the photocatalytic H2 evolution is proceeded by Cl-PhCH2OH oxidation in N,N-dimethylformamide solution, with 4-chlorobenzaldehyde (Cl-PhCHO) generated. The separated photogenerated e- and h+ both participated in the redox reaction of H+ reduction and Cl-PhCH2OH oxidation, considering that the amount of H2 and Cl-PhCHO products are close to 1:1. This work not only facilitates the separation and transfer of PCCs, but also provides directions for the design of efficient photocatalysts and H2 evolution in the organic phase.

Synthesize magnetic ZnFe2O4@C/Cd0.9Zn0.1S catalysts with S-scheme heterojunction to achieve extraordinary hydrogen production efficiency

Suppressing the electron-hole recombination rate of catalyst legitimately is one of the effective strategies to improve photocatalytic hydrogen evolution. Herein, carbon-coated metal oxide, ZnFe2O4@C (ZFO@C), nanoparticles were synthesized and employed to couple with quadrupedal Cd0.9Zn0.1S (CZS) via an ordinary ultrasonic self-assembly method combined with calcination to form a novel ZFO@C/CZS catalyst with step-scheme (S-scheme) heterojunction. The photocatalytic hydrogen evolution reaction (HER) was conducted to verify the enhanced photoactivity of ZFO@C/CZS. The optimal ZFO@C/CZS exhibits an extraordinary photocatalytic HER rate of 111.3 ± 0.9 mmol g-1 h-1 under visible-light irradiation, corresponding to an apparent quantum efficiency as high as (76.2 ± 0.9)% at 450 nm. Additionally, the as-synthesized ZFO@C/CZS composite exhibits high stability and recyclability. The excellent photocatalytic hydrogen evolution performance should arise from the formed S-scheme heterojunction and the unique ZFO@C core-shell structure, which inhibit electron hole recombination as well as provide more reactive sites. The pathway of S-scheme charge transfer was validated through density functional theory calculations and electrochemical measurements. This work provides a rational strategy for the synthesis of unique magnetic S-scheme heterojunction photocatalysts for water splitting under visible light irradiation.

Photocatalytic hydrogen production from seawater by TiO2/RuO2 hybrid nanofiber with enhanced light absorption

Compared to hydrogen production through pure water photocatalysis, the direct utilization of seawater for hydrogen production aligns better with the principles of sustainable development. Seawater, however, contains impurity ions like Na+ and Cl-, which pose higher demands on photocatalysts. It is widely acknowledged that RuO2 and TiO2 demonstrate excellent stability in seawater. Consequently, this study focuses on the model system of RuO2-modified TiO2 for investigating hydrogen production in simulated seawater. TiO2/RuO2 nanofibers (NFs) were synthesized via a one-step electrospinning method, ensuring intimate contact between the two components. The hydrogen production activity of TiO2/RuO2 NFs in simulated seawater nearly matches that in pure water. Remarkably, RuO2 serves as an oxidation cocatalyst, effectively scavenging holes from the valence band of TiO2 and enhancing the separation efficiency of electrons and holes. Interestingly, Cl- ions, similar to RuO2, contribute to reducing excess holes. This study lays the groundwork for future research into hydrogen production from seawater.