The transition to non-platinum group metal (PGM) electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs) is central to achieving sustainable and cost-effective energy conversion. However, the continued widespread use of platinum counter electrodes in electrochemical testing introduces a critical artefact, namely, platinum dissolution, migration through the electrolyte and redeposition onto the working electrode. This potentially skews performance metrics and undermines claims of ‘platinum-free’ sustained ORR activity. This study systematically investigates this issue using a model nitrogen-doped carbon electrocatalyst with inherently low catalytic activity, allowing facile observation of small performance improvements that may be difficult to separate in high-performance catalysts. Platinum wire and graphite rod counter electrodes are compared under load cycling and start-stop conditions in both acidic and alkaline media over 60,000 potential cycles. We demonstrate that platinum contamination from the counter electrode significantly enhances ORR activity and slows performance degradation, effects which are absent when a graphite counter electrode is used. Transmission electron microscopy (TEM) confirms platinum electrodeposition on the working electrode. These findings challenge prevailing experimental protocols and establish the graphite counter electrode as essential for accurate benchmarking of non-PGM catalysts. The work delivers a clear methodological clarification with broad implications for electrocatalyst development and validation.
The transition to non-platinum group metal (PGM) electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs) is central to achieving sustainable and cost-effective energy conversion. However, the continued widespread use of platinum counter electrodes in electrochemical testing introduces a critical artefact, namely, platinum dissolution, migration through the electrolyte and redeposition onto the working electrode. This potentially skews performance metrics and undermines claims of 'platinum-free' sustained ORR activity. This study systematically investigates this issue using a model nitrogen-doped carbon electrocatalyst with inherently low catalytic activity, allowing facile observation of small performance improvements that may be difficult to separate in highperformance catalysts. Platinum wire and graphite rod counter electrodes are compared under load cycling and start-stop conditions in both acidic and alkaline media over 60,000 potential cycles. We demonstrate that platinum contamination from the counter electrode significantly enhances ORR activity and slows performance degradation, effects which are absent when a graphite counter electrode is used. Transmission electron microscopy (TEM) confirms platinum electrodeposition on the working electrode. These findings challenge prevailing experimental protocols and establish the graphite counter electrode as essential for accurate benchmarking of non-PGM catalysts. The work delivers a clear methodological clarification with broad implications for electrocatalyst development and validation.
Photocatalytic overall water splitting (POWS) is a developing method of green hydrogen production that utilises light as an energy source. Lanthanide tantalum perovskite oxynitrides (LnTaON2, Ln = lanthanide) are promising photocatalyst candidates as their valence and conduction band positions are suitable for POWS and their small bandgaps (1.8-2.4 eV) allow for utilisation of visible light. For lanthanides other than lanthanum, LnTaON2 perovskites remain underexplored for photocatalytic water splitting, with little work undertaken to optimise their photocatalytic activity and efficiency. In contrast, many successful synthetic variations have been explored to improve the photocatalytic activity of LaTaON2, including solid solution formation, morphology control and heterojunction formation. An overview of current work into non-lanthanum LnTaON2 photocatalysts is provided, along with the successful strategies utilised to improve the photocatalytic performance of LaTaON2, providing a toolbox of techniques to apply to non-lanthanum LnTaON2 photocatalysts to improve their photocatalytic performance in the future.
The southern Sichuan Basin in China is frequently plagued by particulate matter (PM2.5) pollution events in winter, owing to its unique topographical and meteorological conditions. This study combined the machine learning method with the receptor model to reveal the significance of driving factors and their impacts on PM(2.5 )concentrations. The results indicated that three primary wintertime severe PM(2.5 )pollution episodes in the southern Sichuan Basin were driven by the combination of high temperatures (>283 K), high atmospheric pressure (P) (>980 hPa), high relative humidity (RH) (>80%), weak wind speeds (WS) (<1 m s(-1)) and low boundary layer height (BLH) (<500 m). Emissions were identified as the dominant factor (76.5%), followed by meteorological conditions (12.8%) and atmospheric chemical reactions (10.7%). Secondary sources (25.5%) and transport-related sources (24.7%) were identified as the main contributors to PM(2.5 )concentrations. The sensitivity analysis of secondary inorganic aerosols (SIAs) revealed that the most influential factor was ammonium (NH4+), followed by sulfate (SO42-) and nitrate (NO3-). This study advances our understanding of PM(2.5 )drivers and informs targeted pollution control strategies.
Platinum-gold alloys have attracted attention as promising candidates for next-generation platinum channels due to their cost-effectiveness and enhanced performance on glass substrates. The addition of trace amounts of zirconium is expected to improve chemical stability and tune key properties such as strength and conductivity. To examine the influence of zirconium concentration, density functional theory (DFT) was used to study the structural, thermal and electronic properties of Pt-5Au-xZr alloys with zirconium contents ranging from 0.0 wt% to 5.0 wt%. The results show that zirconium addition effectively improves the stability of Pt-5Au-xZr crystals. Regarding mechanical properties, the toughness of Pt-5Au-xZr alloys initially increases and then decreases with added zirconium, while hardness exhibits an opposite trend. Notably, at 2.0 wt% zirconium, the Pugh's ratio peaks at 5.197 GPa and hardness reaches its lowest value of 2.215 GPa. Regarding high-temperature performance, Pt-5Au-2.0Zr exhibits excellent stability. At 1600 K, its thermal expansion coefficient is measured to be 3.60 & times; 10-5 K-1. Density of states (DOS) analysis confirms that zirconium incorporation modifies the electronic states near the Fermi level: at moderate contents, electronic delocalisation lowers the dislocation slip barrier, while excessive contents induce partial localisation, strengthening rigidity but reducing ductility. Consequently, Pt-5Au-2.0Zr achieves an optimal balance of toughness and high-temperature stability. This study provides a comprehensive analysis of different zirconium contents on the performance of Pt-5Au alloys, delivering important theoretical guidance for their potential engineering applications.
