Increasing the Photocatalytic Hydrogen Generation Activity of CdS Nanorods by Introducing Interfacial and Polarization Electric Fields

Plant-Based Phytochemicals for Synthesis of Z-Scheme In2O3/CdS Heterostructures: DFT Analysis and Photocatalytic CO2 Reduction to HCOOH and CO

Photocatalytic CO2 reduction shows potential for mitigating industrial emissions. Z-scheme In2O3/CdS(bio) heterostructures (25 nm, 217.0 m2 g-1 surface area) with a more negative conduction band synthesized using phytochemicals present in Aegle marmelos with short microwave irradiation inhibit CdS(bio) photocorrosion forming SO42-. In2O3/CdS(bio) increased the photocurrent density (0.82 μA cm-2) and CO2 adsorption (0.431 mmol g-1) significantly compared to CdS(bio) and In2O3(bio) NPs. Heterostructures increased decay time and reduced PL intensity by 46.28 and 61.80% over those of CdS(bio) and In2O3(bio) NPs. Density functional theory (DFT)-optimized geometry, band structure analysis, and density of states (DOS) studies indicate that the DOS of CdS is modified with In2O3 incorporation, enhancing charge separation. Optimal 0.4In2O3/CdS(bio) heterostructures exhibit remarkable CO2 conversion to HCOOH/CO production of 514.4/162 μmol g-1 h-1 (AQY 4.44/2.45%), surpassing CdS(bio) and In2O3(bio) by 9 and 6.5 times, and retain their morphological and structural stability. This study provides valuable insight for developing bio-based CdS heterostructures for photocatalytic CO2 reduction.

A general strategy for the enhanced H2 production performance of CdS/noble metal sulfide nanorods photocatalysts by cation exchange

In this work, we report a series of noble metal (Ag, Au, Pt, etc.) sulfides that act as co-catalysts anchoring on CdS nanorods (NRs) obtained via a cation exchange strategy to promote photocatalytic hydrogen evolution. CdS NRs are first generated via a hydrothermal routine, noble metal sulfides are then in-situ grown on CdS NRs by a cation exchange method. CdS/Ag2S, CdS/Au2S and CdS/PtS NRs show improved hydrogen production rates (2506.88, 1513.17 and 1004.54 μmol g-1h-1, respectively), approximately 18, 11 and 7 times higher than CdS NRs (138.27 μmol g-1h-1). Among CdS/noble metal sulfide NRs, CdS/Ag2S NRs present the best H2 production performance. The apparent quantum efficiency (AQE) of CdS/Ag2S NRs achieves 3.11 % at λ = 370 nm. The improved photocatalytic performance of CdS/noble metal sulfide NRs dues to the following points: i) Noble metal sulfides on CdS NRs are beneficial for elevating light-absorbing and light-utilizing capacities, contributing to generating more photoexcited charges; ii) Noble metal sulfides are in-situ grown on CdS NRs as electron acceptors by a cation exchange method, thus the photoexcited electrons generated by CdS NRs rapidly migrate to the surface of noble metal sulfides, successfully accelerating the carriers separation efficiency. This series of noble metal sulfides acting as co-catalysts anchoring on CdS NRs offer new insights into the construction principles of high-performance photocatalytic hydrogen evolution catalysts.

Inducing spin polarization via Co doping in the BiVO4 cell to enhance the built-in electric field for promotion of photocatalytic CO2 reduction

The efficiency of CO2 photocatalytic reduction is severely limited by inefficient separation and sluggish transfer. In this study, spin polarization was induced and built-in electric field was strengthened via Co doping in the BiVO4 cell to boost photocatalytic CO2 reduction. Results showed that owing to the generation of spin-polarized electrons upon Co doping, carrier separation and photocurrent production of the Co-doped BiVO4 were enhanced. CO production during CO2 photocatalytic reduction from the Co-BiVO4 was 61.6 times of the BiVO4. Notably, application of an external magnetic field (100 mT) further boosted photocatalytic CO2 reduction from the Co-BiVO4, with 68.25 folds improvement of CO production compared to pristine BiVO4. The existence of a built-in electric field (IEF) was demonstrated through density functional theory (DFT) simulations and kelvin probe force microscopy (KPFM). Mechanism insights could be elucidated as follows: doping of magnetic Co into the BiVO4 resulted in increased the number of spin-polarized photo-excited carriers, and application of a magnetic field led to an augmentation of intrinsic electric field due to a dipole shift, thereby extending carrier lifetime and suppressing charges recombination. Additionally, HCOO- was a crucial intermediate in the process of CO2RR, and possible pathways for CO2 reduction were proposed. This study highlights the significance of built-in electric fields and the important role of spin polarization for promotion of photocatalytic CO2 reduction.

Directional Charge Pumping from Photoactive P-doped CdS to Catalytic Active Ni2 P via Funneled Bandgap and Bridged Interface for Greatly Enhanced Photocatalytic H2 Evolution

Loading cocatalysts onto semiconductors is one of the most popular strategies to inhibit charge recombination, but the efficiency is generally hindered by the localized built-in electric field and the weakly connected interface. Here, this work designs and synthesizes a 1D P-doped CdS nanowire/Ni2 P heterojunction with gradient doped P to address the challenges. In the composite, the gradient P doping not only creates a funneled bandgap structure with a built-in electric field oriented from the bulk of P-CdS to the surface, but also facilitates the formation of a tightly connected interface using the co-shared P element. Consequently, the photogenerated charge carriers are enabled to be pumped from inside to surface of the P-CdS and then smoothly across the interface to the Ni2 P. The as-obtained P-CdS/Ni2 P displays high visible-light-driven H2 evolution rate of ≈8265 µmol g-1 h-1 , which is 336 times and 120 times as that of CdS and P-CdS, respectively. This work is anticipated to inspire more research attention for designing new gradient-doped semiconductor/cocatalyst heterojunction photocatalysts with bridged interface for efficient solar energy conversion.