Catalysis Towards Sustainability

Catalysis plays a pivotal role in advancing sustainability by enabling cleaner, more efficient chemical transformations essential for energy, environment, and materials innovation. As humanity faces pressing challenges like climate change, energy insecurity, and resource depletion, catalysis offers viable pathways toward renewable fuels, green chemicals, and circular processes. Harnessing the power of catalytic science will not only mitigate environmental impact but also shape a more resilient, equitable, and sustainable future for generations to come. This special issue on Catalysis Towards Sustainability features 18 peer-reviewed contributions, including three comprehensive reviews and two forward-looking perspectives from leading researchers across the globe. The collected works explore a diverse array of topics at the intersection of catalysis and sustainability, with particular emphasis on the development of advanced materials for photocatalysis, biomass conversion, and other critical energy conversion and storage technologies. Cutting-edge analytical techniques enabling in-situ and operando observations of catalytic processes under real working conditions are also showcased, underscoring the progress in understanding and optimizing catalytic systems for sustainable applications.

Photocatalysis plays a vital role in advancing sustainability by harnessing solar energy to drive chemical reactions for clean fuel production, pollutant degradation, and CO₂ reduction. As a light-driven, low-energy process, it offers a green and efficient alternative to traditional catalytic methods that often rely on harsh conditions or fossil-based energy inputs. By enabling the conversion of abundant and renewable resources into valuable products, photocatalysis supports the development of environmentally friendly technologies for energy and environmental applications. This special issue presents a review, a perspective, and four research articles highlighting recent advances in photocatalytic materials for diverse applications. Ying-Chih Pu and co-workers (article 202400329) reviewed recent advances in understanding charge carrier dynamics at the heterojunctions of semiconductor nanoheterostructures for photocatalytic solar fuel generation. Time-resolved spectroscopic techniques such as transient absorption spectroscopy (TAS), time-resolved photoluminescence, and in-situ TAS were highlighted for their ability to capture ultrafast and long-lived charge behaviors, providing deep insights into excitation, separation, and recombination processes. The review emphasizes how integrating these techniques with material engineering through nanostructure tuning and co-catalyst incorporation can enhance charge separation and light absorption, thereby informing the rational design of more efficient photocatalysts for water splitting and CO₂ reduction. Hisao Yoshida (article 202400439) presented a perspective on heterogeneous photocatalytic organic transformations using metal-loaded TiO₂ photocatalysts, with a focus on dehydrogenative cross-coupling and alkene addition reactions. Through mechanisms such as radical addition-elimination, radical-radical coupling, and radical anti-Markovnikov addition, the study demonstrated how cocatalyst selection, particularly Pt, Pd, and Pd-Au, critically influences product selectivity and efficiency. Despite challenges like low quantum efficiency and limited visible light absorption, strategic catalyst design, surface modification, and reactor engineering are highlighted as promising approaches to advance photocatalytic methodologies for sustainable organic synthesis.

Tso-Fu Mark Chang and co-workers (article 202400285) studied the enhancement of photocatalytic activity in BiFeO₃ nanoparticles through electrical polarization (poling) to improve their performance under visible light. Poling aligned the ferroelectric domains, significantly boosting charge separation and enabling near-complete degradation (99%) of Indigo dye compared to 56% with unpoled BiFeO₃. The poling-treated BiFeO₃ maintained 65% of its activity after multiple cycles, demonstrating both high efficiency and durability for environmental remediation applications. Takashi Hisatomi and co-workers (article 202400321) studied the synthesis of Al-doped LaTiO₂N photocatalysts via flame spray pyrolysis to enhance H₂ evolution under visible light. By using a metastable La–Ti oxide precursor and incorporating Al doping, the process suppressed mesopore formation and Ti³⁺ generation during nitridation, resulting in improved apparent quantum yield. The findings highlight the importance of designing isostructural oxide precursors to minimize structural changes and optimize photocatalytic activity for sustainable H₂ production. Akihide Iwase and co-workers (article 202400371) developed a Z-scheme photocatalyst system for visible-light-driven water splitting, combining (CuGa)_0.5ZnS₂ as the H₂-evolving photocatalyst and TaON as the O₂-evolving photocatalyst. Enhanced performance was achieved through the coloading of Ir and CoO_x cocatalysts on TaON and the use of reduced graphene oxide as a solid-state electron mediator to facilitate efficient charge transfer. This novel combination of non-metal oxide materials offers valuable insights into designing advanced Z-scheme systems for sustainable solar water splitting. Haoxin Mai and co-workers (article 202400397) developed a rapid and effective strategy for designing Al-doped Mn₃O₄-based photocatalysts by integrating density functional theory (DFT), machine learning (ML), and experimental validation. Al_0.5Mn_2.5O₄ was identified as an optimal composition due to its favorable bandgap and charge mobility, and further performance was achieved through the formation of heterojunctions with Ag₃PO₄. The optimized Al_0.5Mn_2.5O₄/35%-Ag₃PO₄ composite exhibited a 27-fold enhancement in photocatalytic dye degradation efficiency, showcasing the power of DFT- and ML-guided design for advancing environmental remediation technologies.

Biomass conversion and valorization are essential for achieving sustainability by transforming renewable organic resources into valuable fuels, chemicals, and materials. This approach reduces reliance on fossil fuels, minimizes waste, and promotes a circular carbon economy by utilizing agricultural and industrial by-products. Through innovative catalytic processes, biomass valorization supports the development of greener technologies and contributes to energy security and environmental preservation. This special issue presents a review and two research articles showcasing recent developments in advanced catalytic materials for efficient and sustainable biomass conversion. Jeong Gil Seo and co-workers (article 202400369) reviewed recent advancements in upgrading furfural and its derivatives into green transport fuels and fuel precursors through carbon–carbon coupling reactions, such as aldol condensation and hydroxyalkylation-alkylation. Emphasis was placed on catalyst development, process integration, and emerging strategies, including hydrophobic catalyst modifications and tandem catalytic systems, to improve efficiency, selectivity, and catalyst stability. While significant progress has been made, challenges related to H₂ consumption, catalyst deactivation, and side reactions remain, highlighting the need for continued innovation to advance the industrial viability of biomass-to-fuel technologies. Keiichi Tomishige and co-workers (article 202400363) developed a low-metal-loading ReO_x-Pd/CeO₂ catalyst with enhanced activity, stability, and reusability for the consecutive deoxydehydration and hydrogenation of biomass-derived vicinal diols. A 0.5 wt% Re catalyst outperformed the higher-loading counterpart by achieving faster conversion rates, a three-fold reduction in deactivation, and full regeneration under mild thermal conditions. These findings demonstrate a promising strategy for designing efficient, recyclable catalysts for biomass valorization, supporting greener and more sustainable chemical processes. Yutaka Amao and co-workers (article 202500008) investigated the biocatalytic production of isocitrate from low-concentration gaseous CO₂ and biobased 2-oxoglutarate using yeast-derived isocitrate dehydrogenase (IDH). The addition of divalent manganese ions was found to significantly enhance the IDH-catalyzed carboxylation reaction, enabling efficient C–C bond formation with CO₂. This study demonstrates a promising strategy for CO₂ utilization under mild conditions, contributing to the development of carbon recycling technologies through enzymatic catalysis.

Critical energy conversion technologies, such as ammonia decomposition, refrigerant decomposition, hydrogenation, methane oxidation, organic electrosynthesis, and CO₂ conversion, are pivotal in transitioning to a sustainable, low-carbon energy future. These processes enable the efficient transformation of energy carriers and waste compounds into clean fuels and valuable chemicals, thereby reducing greenhouse gas emissions and dependence on fossil resources. Advancing these technologies through innovative catalysts and reaction systems is essential for realizing scalable and economically viable sustainable energy solutions. In addition to energy conversion, the development of sustainable materials for energy storage, such as supercapacitors, plays a crucial role in balancing supply and demand, improving energy efficiency, and supporting renewable energy integration. This special issue presents a review and seven research articles that highlight recent progress in the development of advanced materials for energy conversion and storage technologies. Yongju Yun and co-workers (article 202400406) reviewed recent advances in Co-based catalysts for ammonia decomposition as a route to carbon-free H₂ production, highlighting their catalytic performance and economic advantages. Strategies to enhance activity include optimizing Co particle size and dispersion, incorporating secondary metals or promoters, tuning support properties, and employing heteroatom doping to improve reaction kinetics and catalyst stability. The review also emphasizes the need for in-situ characterization techniques and operational considerations under pressurized conditions to guide the rational design of scalable, cost-effective alternatives to Ru-based catalysts for industrial H₂ production. Dong-woo Cho and co-workers (article 202400306) investigated the long-term stability of metal-impregnated γ-Al₂O₃ catalysts (M = Mg, Ni, Co, Zn, Cu) for HFC-134a decomposition under harsh industrial conditions. Among the tested catalysts, Mg/γ-Al₂O₃ demonstrated the highest durability, maintaining over 70 % conversion for 72 hours due to its high concentration of weak Lewis acid sites and resistance to deactivation. The formation of MgF₂ was found to inhibit the full fluorination of γ-Al₂O₃, reducing AlF₃ formation and preserving catalyst structure, highlighting Mg impregnation as an effective strategy for improving catalyst performance in fluorocarbon decomposition applications. Seok Ki Kim and co-workers (article 202400341) explored strategies to mitigate green-oil-induced deactivation in acetylene hydrogenation using Pd catalysts supported on various carbon materials. Carbon-supported catalysts, especially those with higher surface areas like carbon nanotubes, showed significantly greater stability than alumina-supported ones, with surface area emerging as the key factor influencing deactivation resistance. The study underscores the importance of optimizing textural properties, rather than solely chemical characteristics, for designing durable catalysts suited to high-acetylene environments from nonpetroleum sources. Sung Bong Kang and co-workers (article 202400358) investigated how nitric acid (NA) treatment influences the performance of Pt/TiO₂ catalysts in methane oxidation, focusing on the relationship between acid concentration, Pt dispersion, and catalytic activity. Controlled NA treatment enhanced surface acidity and Pt dispersion, leading to significantly improved catalytic efficiency, while excessive acid use caused Pt aggregation and reduced performance. The study provides a straightforward strategy for optimizing Pt-based oxidation catalysts and offers valuable insights for designing advanced materials for environmental methane control. Tomoyuki Kurioka and co-workers (article 202400420) developed Au/poly(3-methoxythiophene) (Au/P3MeOT) hybrid electrodes through simultaneous electrochemical doping of the polymer and Au electrodeposition to enhance the anodic oxidation of 1-propanol, an important model reaction involved in organic electrosynthesis. The applied potential during synthesis was found to control Au particle morphology and distribution, with optimal hybridization occurring when both doping and Au reduction occurred simultaneously. The resulting hybrid materials demonstrated strong and stable electrocatalytic performance, offering a versatile platform for designing tailor-made catalysts for alcohol oxidation and related electrochemical reactions.

Yung-Jung Hsu and co-workers (article 202400409) demonstrated effective CO₂ decomposition using a non-thermal atmospheric pressure plasma jet (NTAPPJ) system coupled with CuO catalysts, achieving a conversion rate of 37.98% and improved energy efficiency. The synergy between plasma activation and CuO catalysts, particularly the formation of oxygen vacancies, was identified as key to facilitating CO₂ adsorption and dissociation. This first application of an NTAPPJ-CuO system for CO₂ conversion offers promising potential for plasma-catalyst strategies, with future improvements needed in reducing energy consumption for broader application. Chia-Yu Lin and co-workers (article 202500080) developed a geopolymer/graphene-cobalt phthalocyanine (graphene-CoPc) composite for the integrated capture and electroreduction of low-concentration CO₂ to CO under simulated biogas conditions. The geopolymer matrix enhanced electrical conductivity and CO₂ adsorption, resulting in a significant boost in turnover frequency and Faradaic efficiency compared to pristine graphene-CoPc. This composite achieved 93.7% Faradaic efficiency at low overpotential, offering a promising, cost-effective strategy for CO₂ valorization using renewable electricity. Ajayan Vinu and co-workers (article 202500037) developed nitrogen and sulfur co-doped nanoporous biocarbons from casein and dithiooxamide with exceptionally high surface areas and microporosity for supercapacitor applications. The optimized material achieved a specific capacitance of 178 F g⁻¹ at 0.5 A g⁻¹ and maintained 93.2% capacitance after 3000 cycles, owing to the synergistic effects of N, S, and O heteroatoms providing redox-active sites and enhanced conductivity. This green, low-cost synthesis strategy offers a promising route for designing high-performance electrode materials for next-generation energy storage devices.

In-situ and operando synchrotron radiation techniques are powerful tools for unveiling the structural, electronic, and chemical dynamics of catalysts under real working conditions. These advanced characterization methods provide critical insights into reaction mechanisms and active sites, enabling the rational design of more efficient and durable catalytic systems. Yan-Gu Lin and co-workers (article 202500029) provided a perspective on the use of advanced in-situ and operando synchrotron radiation techniques to investigate dynamic structural and electronic changes at electrified solid–liquid interfaces in electrocatalytic systems. These methods, including X-ray scattering and spectroscopy, enable the direct observation of active sites and reaction intermediates, offering critical insights into the mechanisms of electrochemical processes. The authors also proposed a practical framework, the in-situ/operando electrocatalytic mechanism probing map, to guide systematic studies of complex catalytic interfaces and accelerate the development of efficient electrocatalysts.

This special issue on Catalysis Towards Sustainability showcases recent advances in photocatalysis, biomass conversion, energy conversion and storage, as well as in-situ/operando characterization techniques, reflecting the multifaceted efforts to build a more sustainable future through catalytic science. The development of innovative materials and reaction systems for applications such as H₂ production, CO₂ reduction, organic synthesis, and supercapacitor technologies highlights the critical role of catalysis in enabling green energy solutions and carbon-neutral processes. Significant progress has been made in designing efficient, cost-effective, and durable catalysts; however, challenges remain in scaling up these technologies, enhancing selectivity, and improving long-term stability under realistic conditions. Emerging strategies, such as ML-guided catalyst design and advanced in-situ/operando analysis, offer promising pathways to accelerate catalyst discovery and deepen mechanistic understanding. Continued interdisciplinary collaboration and integration of fundamental research with practical applications will be key to overcoming existing barriers and driving transformative progress in sustainable catalysis.