Engineering active sites in a controllable manner plays a critical role in developing catalysts with desired catalytic performance. A reliable and tunable molecular engineering strategy is presented to boost the oxygen reduction reaction (ORR) performance of single-atom catalysts (SACs) by manipulating the steric hindrance effect of metalloporphyrins. The results demonstrate that the metalloporphyrin molecules with four tert-butylphenyl groups as steric hindrance moieties can be used to prepare various SACs with targeted active sites on conductive carbon black (CB). It is found that the single iron catalyst on CB prepared using tert-butylphenyl iron-porphyrins as a precursor (denoted as t-Fe-800/CB) exhibits significantly enhanced ORR performance compared with the Fe-800/CB catalyst prepared from unsubstituted iron-porphyrin. Moreover, the t-Fe-800/CB catalyst exhibits superior ORR performance relative to t-Mn-800/CB and t-Co-800/CB with different metal centers, indicating that the intrinsic ORR activity originates from single Fe sites. The remarkable ORR properties are mainly attributed to the enhanced intrinsic activity and density of Fe active sites, as well as improved conductivity and mass transfer induced by the steric hindrance effect. The optimized t-Fe-800/CB catalyst also delivers impressive performance in both flexible and aqueous Zn–air batteries. This study offers a new perspective for the development of advanced SAC electrocatalysts for energy conversion applications.

The transition from a linear economy to a circular carbon economy urgently requires sustainable and efficient technologies for converting non-fossil biomass and waste plastics into fuels and high-value chemicals. Solar-driven photocatalytic technology has emerged as a promising strategy due to its mild reaction conditions and potential for selective transformation, which addresses the limitations of traditional recycling and conversion methods (e.g., high energy consumption, harsh conditions, and poor selectivity). However, current photocatalytic valorization systems still suffer from insufficient activity and selectivity, mainly due to the inability to precisely regulate reaction pathways. Considering that selective bond activation (especially C–H and C–C bond activation) is the key determinant, this review focuses on the photocatalytic valorization of biomass and plastics, classifies reaction pathways based on dominant bond selectivity, and mainly emphasizes the contrast between C–H and C–C bond activation. This classification approach overcomes the limitations of traditional substrate-based classification, providing new insights for the rational design of highly selective photocatalytic systems to realize the valorization of biomass and waste plastics.

Photocatalytic CO₂ reduction for solar fuel production is a critical technology enabling carbon cycling and efficient renewable energy storage. However, conversion efficiency remains severely limited by bottlenecks such as rapid recombination of photogenerated charge carriers, high activation barriers for CO₂ molecules, and inadequate catalyst stability. To overcome these challenges, this study constructed an in situ ZrO₂ nanoparticle protective layer on CdS nanospheres, yielding a ZrO₂/CdS-20 (ZOCS-20) core-shell composite photocatalyst. Under light conditions, this catalyst demonstrated exceptional performance, with a CO production rate of 330.23 μmol/(g·h) and near 100% CO selectivity. Systematic characterization and density functional theory (DFT) calculations reveal the underlying enhancement mechanism. The core-shell heterostructure suppresses charge recombination through interfacial engineering, significantly improving charge separation efficiency and carrier transport kinetics while enhancing material stability. Crucially, strong electron coupling at the ZrO₂/CdS interface shifts the d-band center of catalyst toward the Fermi level, strengthening CO₂ chemisorption and lowering its activation barrier. The optimized electronic interface also reduces the energy barrier for forming the ^*COOH intermediate, substantially decreasing activation energy of the rate-determining step (RDS) and providing additional thermodynamic driving force. This work elucidates an interface-band synergy enhancement mechanism, offering both theoretical insights and experimental guidance for the design of efficient photocatalytic materials.

Proton-exchange-membrane water electrolysis (PEMWE) is a leading technology for green hydrogen production, yet its performance and durability at high current densities are increasingly constrained by transport and interfacial losses within the porous transport layer (PTL). Positioned between the flow field and the catalyst layer, the PTL governs coupled two-phase water/oxygen transport, electronic conduction, heat dissipation, and mechanical support under harsh anodic conditions. In particular, the counter-current flow of liquid water and evolved oxygen, bubble nucleation and detachment dynamics, interfacial contact resistance, and corrosion-induced degradation collectively dictate cell efficiency and lifetime. This review summarizes recent advances in the development of high-performance Ti-based PTLs for PEMWE. Key thermal/electrical conduction and mass-transport mechanisms in PTLs, together with their influence on cell performance, are discussed. PTL performance can be improved through rational control of substrate microstructure, protective coatings, and surface modification. Two-phase transport can be enhanced by tuning pore architecture and wettability, while PTL–CL contact and catalyst utilization can be improved by introducing a microporous top layer. In addition, various PTL fabrication and processing strategies are comparatively discussed to highlight their respective advantages, limitations, and roles in enabling high-performance PEMWE operation.

High NO_x emissions pose a critical challenge for ammonia engines. This study proposes ammonia post-injection as a strategy to achieve in-cylinder NO_x active reduction in ammonia direct-injection engines, offering an innovative approach for NO_x emission control. Computational fluid dynamics (CFD) simulation results elucidate the characteristics of ammonia combustion and NO_x evolution under ammonia post-injection conditions. The post-injected ammonia can efficiently reduce the in-cylinder NO_x it encounters, leading to a significant decrease in NO_x concentration. Chemical kinetics analysis was conducted to reveal the underlying mechanisms and reaction pathways of the SNCR effect on NO_x. The reduction of NO_x primarily proceeds through the reactions between NO/NO₂ and NH/NH₂. NO is reduced via three pathways, yielding NNH (by NH₂), N₂O (by NH), and N₂ (by NH and NH₂), respectively. In contrast, NO₂ is reduced via a single pathway that yields N₂O under the action of NH and NH₂. NH₂ plays the overwhelmingly dominant role in reducing both NO and NO₂. The effectiveness and feasibility of ammonia post-injection in reducing NO_x emissions were evaluated through engine experiments. The experimental results demonstrate that the ammonia post-injection strategy enables significant NO_x reduction for ammonia direct-injection engines. In the current work, a 14.4% NO_x reduction was achieved without compromising combustion efficiency by appropriately delaying the ammonia post-injection timing, confirming the great potential of ammonia post-injection in NO_x emission control.

A series of layer-by-layer organic photovoltaics (LOPVs) were constructed using D18 as the donor and L8-BO, featuring exciton self-dissociation characteristics, as acceptor. A trace amount of high crystallinity, high-hole-mobility polymer P66 was intentionally introduced into the L8-BO layer to enhance the hole transport. The power conversion efficiency (PCE) of the LOPVs improved from 18.97% to 19.81% upon the addition of 0.005 wt.% P66 to the L8-BO layer, originating from the concurrent increases in short-circuit current density from 26.87 to 27.72 mA/cm² and fill factor from 78.61% to 79.39%. The introduction of P66 into the L8-BO layer forms an efficient hole-transport network, promoting the transport of holes generated by exciton self-dissociation in L8-BO. In addition, introducing P66 optimizes molecular packing, thereby enhancing charge extraction and transport within active layers. The universality of incorporating P66 into acceptor layers is further demonstrated in a series of LOPVs with different acceptors. This work indicates that introducing materials with high hole mobility and crystallinity into the acceptor layer is a promising strategy for boosting the performance of LOPVs.

Solid-state thermoelectric (TE) power generation through the direct conversion of a temperature difference into electricity has received worldwide attention. In this work, a segmented GeTe/BST-SKD TE module is optimized and fabricated to achieve outstanding power density and energy conversion efficiency. To enable high module-level TE performance, p-type GeTe with a ZT_max of 2.47 is used, while p-type BST (Bi_2−xSb_xTe₃, with high ZT in the low temperature range) and n-type SKD (skutterudite, Yb_0.3Co₄Sb₁₂) are optimized to reach ZT_max values of 1.38 and 1.33, respectively. Furthermore, module structure optimization is conducted using multiphysics-field simulations for three shape factors, including the segmentation ratio, height-to-area ratio, and cross-sectional area ratio between p- and n-type legs. When the three factors are 0.35, 0.67 mm⁻¹, and 1.85, respectively, both the maximum power density and energy conversion efficiency reach their optimal values. Finally, Ni foil is applied at the GeTe/BST interface to serve as both a metallization layer and a diffusion barrier, minimizing internal contact resistances and enhancing high-temperature stability. The maximum power density and energy conversion efficiency of the segmented module are increased by 35% and 21%, respectively, compared with those of the unsegmented one. The segmented module achieves a substantial power output of ~0.43 W at ΔT = 500 K, corresponding to a power density of 0.35 W/cm² per module area and 143 W kg⁻¹ per module weight, with an effective material-level power density of 1.51 W/cm². The segmented module achieves an outstanding energy conversion efficiency of 12.7%, demonstrating the effectiveness of the optimized leg-segmentation strategy for high-performance solid-state energy harvesting.