Bismuth vanadate (BiVO₄) is a promising photoanode material for efficient photoelectrochemical (PEC) water splitting, whereas its performance is inhibited by detrimental surface states. To solve the problem, herein, a low-cost organic molecule 1,3,5-benzenetricarboxylic acid (BTC) is selected for surface passivation of BiVO₄ photoanodes (BVOs), which also provides bonding sites for Co²⁺ to anchor, resulting in a Co-BTC-BVO photoanode. Owing to its strong coordination with metal ions, BTC not only passivates surface states of BVO, but also provides bonding between BVO and catalytic active sites (Co²⁺) to form a molecular cocatalyst. Computational study and interfacial charge kinetic investigation reveal that chemical bonding formed at the interface greatly suppresses charge recombination and accelerates charge transfer. The obtained Co-BTC-BVO photoanode exhibits a photocurrent density of 4.82 mA/cm² at 1.23 V vs. reversible hydrogen electrode (RHE) and a low onset potential of 0.22 V_RHE under AM 1.5 G illumination, which ranks among the best photoanodes coupled with Co-based cocatalysts. This work presents a novel selection of passivation layers and emphasizes the significance of interfacial chemical bonding for the construction of efficient photoanodes.

Oxygen vacancies in oxygen evolution cocatalysts (OECs) can significantly improve the photoelectrochemical (PEC) water splitting performance of photoanodes. However, OECs with abundant oxygen vacancies have a poor stability when exposing to the highly-oxidizing photogenerated holes. Herein, we partly fill oxygen vacancies in a MnCo₂O_x OEC with N atoms by a combined electrodeposition and sol-gel method, which dramatically improves both photocurrent density and stability of a BiVO₄ photoanode. The optimized N filled oxygen vacancy-rich MnCo₂O_x/BiVO₄ photoanode (3 at.% of N) exhibits an outstanding photocurrent density of 6.5 mA·cm⁻² at 1.23 V_RHE under AM 1.5 G illumination (100 mW·cm⁻²), and an excellent stability of over 150 h. Systematic characterizations and theoretical calculations demonstrate that N atoms stabilize the defect structure and modulate the surface electron distribution, which significantly enhances the stability and further increases the photocurrent density. Meanwhile, other heteroatoms such as carbon, phosphorus, and sulfur are confirmed to have similar effects on improving PEC water splitting performance of photoanodes.

The electrochemical N₂ reduction reaction (NRR) represents a green and sustainable route for NH₃ synthesis under ambient conditions. However, the mechanism of N₂ activation in the electrocatalytic NRR remains unclear. Herein, we found that the high spin state Mn³⁺-Mn³⁺ pairs induced by oxygen vacancy in MnO₂ nanosheets greatly enhance the catalytic activities. The strong electron transfer between d orbital of Mn and orbital of N₂ forces the N₂ to be of radical nature, which activates the hydrogenation process and weakens the N≡N bond. Based on the density functional theory (DFT) calculation results, we precisely designed mesoporous MnO₂ nanosheets with rich oxygen vacancies via using methyltriphenylphosphonium bromide (MPB) to induce more Mn³⁺-Mn³⁺ pairs (Mn^3-3-MnO₂), which can achieve a fairly high ammonia yield of up to 147.2 µg·h⁻¹·mg_cat⁻¹_. at −0.75 V vs. reversible hydrogen electrode (RHE) and a high Faradaic efficiency (FE) of 11%. Furthermore, these mesoporous MnO₂ nanosheets exhibit the superior durability with negligible changes in both NH₃ yield and FE after a consecutive 6-recycle test and the current density electrolyzed over a 24-hour period. Our findings offer an approach to designing highly active transition metal catalysts for electrocatalytic nitrogen reduction.

Coupling graphitic carbon nitride (CN) with carbonaceous materials is an effective strategy to improve photocatalytic performance, but the contributions of carbonaceous materials are not fully understood. Herein, a new type of carbon/CN (CCN) complex photocatalyst is synthesized with a 6-fold enhancement of H₂ evolution rate compared to that of pristine CN. The role of carbon in photocatalytic H₂ evolution reaction is systemically studied and it is experimentally and theoretically revealed that carbon mainly contributes to the improved capability of exciton dissociation and enhanced electric conductivity for charge transfer, leading to an increased population of photo-carriers for photocatalytic reactions. Interestingly, the enhanced light absorption originated from carbon barely generates charge carriers for H₂ evolution activity. These new findings will inspire the rational design of carbon-based photocatalysts for efficient solar fuel production.

The development of low-cost and high-active cocatalysts is one of the most significant links for photocatalytic water splitting. Herein, a novel strategy of electron delocalization modulation for transition metal sulfides has been developed by anion hybridization. P-modified CoS₂ (CoS₂|P) nanocrystals were firstly fabricated via a gas-solid reaction and coupled with CdS nanorods to construct a composite catalyst for solar H₂ evolution reaction (HER). The CdS/CoS₂|P catalyst shows an HER rate of 57.8 μmol·h⁻¹, which is 18 times that of the bare CdS, 8 times that of the CdS/CoS₂, and twice that of Pt/CdS. The reduced energy barrier and suppressed reverse reaction for HER on the catalyst have been predicted and explained by density functional theory (DFT) calculation. The underlying design strategy of novel cocatalysts by electron delocalization modulation may shed light on the rational development of other advanced catalysts for energy conversion.

Graphitic carbon nitride (g-C₃N₄, CN) exhibits inefficient charge separation, deficient CO₂ adsorption and activation sites, and sluggish surface reaction kinetics, which have been recognized as the main barriers to its application in CO₂ photocatalytic reduction. In this work, carbon quantum dot (CQD) decoration and oxygen atom doping were applied to CN by a facile one-step hydrothermal method. The incorporated CQDs not only facilitate charge transfer and separation, but also provide alternative CO₂ adsorption and activation sites. Further, the oxygen-atom-doped CN (OCN), in which oxygen doping is accompanied by the formation of nitrogen defects, proves to be a sustainable H⁺ provider by facilitating the water dissociation and oxidation half-reactions. Because of the synergistic effect of the hybridized binary CQDs/OCN addressing the three challenging issues of the CN based materials, the performance of CO₂ photocatalytic conversion to CH₄ over CQDs/OCN-x (x represents the volume ratio of laboratory-used H₂O₂ (30 wt.%) in the mixed solution) is dramatically improved by 11 times at least. The hybrid photocatalyst design and mechanism proposed in this work could inspire more rational design and fabrication of effective photocatalysts for CO₂ photocatalytic conversion with a high CH₄ selectivity.

Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications. However, due to the large size of Na⁺, most Na⁺ host structures resembling their Li+ counterparts show sluggish ion mobility and destructive volume changes during Na ion (de)intercalation, resulting in unsatisfactory rate and cycling performances. Herein, we report a new type of sodium iron phosphate (Na_0.71Fe_1.07PO₄), which exhibits an extremely small volume change (~ 1%) during desodiation. When applied as a cathode material for SIBs, this new phosphate delivers a capacity of 78 mA·h·g^-1 even at a high rate of 50 C and maintains its capacity over 5, 000 cycles at 20 C. In situ synchrotron characterization disclosed a highly reversible solid-solution mechanism during charging/discharging. The findings are believed to contribute to the development of high-performance batteries based on Earth-abundant elements.

The assembly of hybrid nanomaterials has opened up a new direction for the construction of high-performance anodes for lithium-ion batteries (LIBs). In this work, we present a straightforward, eco-friendly, one-step hydrothermal protocol for the synthesis of a new type of Fe₂O₃-SnO₂/graphene hybrid, in which zero-dimensional (0D) SnO₂ nanoparticles with an average diameter of 8 nm and one-dimensional (1D) Fe₂O₃ nanorods with a length of ~150 nm are homogeneously attached onto two-dimensional (2D) reduced graphene oxide nanosheets, generating a unique point-line-plane (0D-1D-2D) architecture. The achieved Fe₂O₃-SnO₂/graphene exhibits a well-defined morphology, a uniform size, and good monodispersity. As anode materials for LIBs, the hybrids exhibit a remarkable reversible capacity of 1, 530 mA·g⁻¹ at a current density of 100 mA·g⁻¹ after 200 cycles, as well as a high rate capability of 615 mAh·g⁻¹ at 2, 000 mA·g⁻¹. Detailed characterizations reveal that the superior lithium-storage capacity and good cycle stability of the hybrids arise from their peculiar hybrid nanostructure and conductive graphene matrix, as well as the synergistic interaction among the components.

A new type of lead-free, formamidinium (FA)-based halide perovskites, FASnI₂Br, are investigated as light-harvesting materials for low-temperature processed p–i–n heterojunction solar cells with different configurations. The FASnI₂Br perovskite, with a band-gap of 1.68 eV, exhibits optimal photovoltaic performance after low-temperature annealing at 75 ℃. By using C₆₀ as electron-transport layer, the device yields a hysteresis-less power conversion efficiency of 1.72%. The possible use of an inorganic MoO_x film as a new type of independent hole-transport layer for the present tin-based perovskite solar cells is also demonstrated.

Methylammonium bismuth (Ⅲ) iodide single crystals and films have been developed and investigated. We have further presented the first demonstration of using this organic–inorganic bismuth-based material to replace lead/tin-based perovskite materials in solution-processable solar cells. The organic–inorganic bismuth-based material has advantages of non-toxicity, ambient stability, and low-temperature solution-processability, which provides a promising solution to address the toxicity and stability challenges in organolead- and organotin-based perovskite solar cells. We also demonstrated that trivalent metal cation-based organic–inorganic hybrid materials can exhibit photovoltaic effect, which may inspire more research work on developing and applying organic-inorganic hybrid materials beyond divalent metal cations (Pb (Ⅱ) and Sn (Ⅱ)) for solar energy applications.