PtFe and Fe3C nanoparticles encapsulated in Fe–N-doped carbon bowl toward the oxygen reduction reaction

The high-temperature calcination strategy facilitates the formation of alloy atoms but inevitably results in the aggregation and deactivation of the metal particles for the oxygen reduction reaction (ORR) electrocatalysts. Herein, we report the successful encapsulation of Platinum–Iron (PtFe) nanoparticles (∼4.7 nm) in the N-doped hollow carbon hemisphere matrix (NCB) containing Fe–N and Fe₃C without employing high-temperature pyrolysis, which effectively facilitates the well-dispersed Pt nanoparticles and the formation of PtFe nanoalloys. The hollow carbon hemisphere structure contributes to the expansion of the specific surface area and exposure of active sites of the catalyst, meanwhile, the modification of the surface of the carbon nano-bowl from a predominantly Fe to a functional electrocatalyst with a primarily PtFe alloy can boost the ORR catalytic activity and stability. It is found that the Pt3Fe/Fe₃C-NCB catalyst exhibits the optimum ORR performance with a mass activity (0.97 A mg⁻¹_Pt), 5.10 times higher than the commercial Pt/C (0.19 A mg⁻¹_Pt). Pt3Fe/Fe₃C-NCB also displays excellent durability in comparison to the commercial Pt/C after 20,000 potential cycles. Combined with the Physical characterization and the electrochemical test results, Fe₃C-NCB plays a strong metal-support role for the encapsulated PtFe nanoparticles structure, thereby preventing nanoparticle migration and corrosion. Experimental characterization and theoretical calculations show that the appropriate PtFe alloy composition and the strain effect induced by Fe–N/Fe₃C active sites are sufficient to accelerate the detachment of oxygenated species from the alloy surface, resulting in a catalyst with excellent ORR performance.     

Kinetic study of oxygen reduction reaction and PEM fuel cell performance of Pt/TiO2-C electrocatalyst

The electrochemical activity and thermal stability of the Pt/TiO₂-C were evaluated in the oxygen reduction reaction (ORR) in acid medium at different temperatures. The platinum was selectively deposited onto the TiO₂ (E_bg = 2.3 eV) by the photo-irradiation of platinum precursor (Pt⁴⁺→Pt⁰). The Pt/TiO₂-C electrocatalyst prepared was characterized by XRD, TEM/EDS, cyclic and lineal voltammetry techniques. TEM images indicated that platinum nanoparticles (<5 nm) were deposited in agglomerates form around the oxide sites. EDS and XRD results confirm the composition and crystalline structure of Pt/TiO₂-C. The thermal stability and electrochemical activity of the Pt/TiO₂-C for ORR at different temperatures (298–343 K) is higher than Pt/C commercial sample (Pt-Etek). A more favorable apparent enthalpy of activation for Pt/TiO₂-C was greatly influenced by addition of oxide in the catalyst compare to Pt-Etek. Single H₂/O₂ fuel cell performance results of Pt/TiO₂-C show an improvement of the power density with the increase of the temperature.     

Nitrogen doped carbon layer coated platinum electrocatalyst supported on carbon nanotubes with enhanced stability

Enhancement in durability of electrocatalyst is still one of the most important issues in polymer electrolyte fuel cells (PEFCs). Here, we report a structurally coated electrocatalyst supported on carbon nanotubes (CNT), in which platinum (Pt) nanoparticles are coated by nitrogen doped carbon (NC) layers. CNT/NC/Pt/NC shows comparable electrochemical surface area (ECSA) and oxygen reduction reaction (ORR) activity to the non-coated electrocatalyst (CNT/NC/Pt), indicating that NC layer on Pt nanoparticles almost negligibly affects the activities of electrocatalyst; while, CNT/NC/Pt/NC exhibits a higher Pt stability due to the unique structure, in which the Pt nanoparticles are stabilized by the NC layers and Pt aggregation is decelerated proved by TEM measurement. Maximum power density of CNT/NC/Pt/NC reached 604 mW cm^?2 with Pt loading of 0.1 mg_Pt cm^?2, which only decreases by 7% compared to CNT/NC/Pt (650 mW cm^?2). The electrochemical analysis and fuel cell test illustrate that NC layer on Pt nanoparticles enhances the durability without serious deterioration of fuel cell performance.     

Lattice-strained Pt nanoparticles anchored on petroleum vacuum residue derived N-doped porous carbon as highly active and durable cathode catalysts for PEMFCs

High cost and poor durability of Pt-based cathode catalysts for oxygen reduction reaction (ORR) severely hamper the popularization of proton exchange membrane fuel cells (PEMFCs). Tailoring carbon support is one of effective strategies for improving the performance of Pt-based catalysts. Herein, petroleum vacuum residue was used as carbon source, and nitrogen-doped porous carbon (N-PPC) was synthesized using a simple template-assisted and secondary calcination method. Small Pt nanoparticles (Pt NPs) with an average particles size of 1.8 nm were in-situ prepared and spread evenly on the N-PPC. Interestingly, the lattice compression (1.08%) of Pt NPs on the N-PPC (Pt/N-PPC) was clearly observed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), which was also verified by the shift of (111) crystal plane of Pt on N-PPC to higher angles. The X-ray photoelectron spectroscopy (XPS) results suggest that the N-PPC support had a strong effect on anchoring Pt NPs and endowing surface Pt NPs with lowered d band center. Thus, the Pt/N-PPC as a catalyst simultaneously boosted the ORR activity and durability. The specific activity (SA) and mass activity (MA) of the Pt/N-PPC at 0.9 V reached 0.83 mA cm⁻² and 0.37 A mg_Pt⁻¹, respectively, much higher than those of the commercial Pt/C (0.21 mA cm⁻² and 0.11 A mg_Pt⁻¹) in 0.1 M HClO₄. The half-wave potential (E_1/2) of Pt/N-PPC exhibited only a minimal negative shift of 7 mV after 30,000 accelerated durability tests (ADT) cycles. More importantly, an H₂–O₂ fuel cell with a Pt/N-PPC cathode achieved a power density of 866 mW cm⁻², demonstrating that the prepared catalyst has a promising application potential in working environment of PEMFCs.     

ZIF derived mesoporous carbon frameworks with numerous edges and heteroatom-doped sites to anchor nano-Pt electrocatalyst

We report the use of nitrogen-doped three-dimensional carbon frameworks (N-MCF) to promote the catalytic performance of nano-sized Pt electrocatalyst for the catalysis of oxygen reduction reaction (ORR). The N-MCF, obtained by pyrolysis of zeolitic imidazolate framework, provides abundant edges, defects, and heteroatom-doped sites to anchor Pt nanoparticles, leading to strong Pt-support interaction and excellent particle dispersion within its three-dimensional mass transport channels. Electrochemical results show only 8 mV degradation in the half-wave potential after accelerated durability test for the N-MCF supported Pt catalysts. Meanwhile, the mass activity and specific activity of Pt/N-MFC could reach 246 mA mg⁻¹_Pt and 0.276 mA cm⁻² at 0.90 V_RHE, which is better than that of commercial Pt/C. Moreover, the high Pt utilization of Pt/N-MFC (186 mg _Pt kW⁻¹) could reach 1.9 times than that of fuel cell fabricated with commercial Pt/C cathode.     

Highly efficient and ORR active platinum-scandium alloy-partially exfoliated carbon nanotubes electrocatalyst for Proton Exchange Membrane Fuel Cell

Oxygen reduction reaction (ORR) in Proton Exchange Membrane Fuel Cell (PEMFC) is the most sluggish reaction, which impedes the performance and commercialization of PEMFC. Platinum-based alloys show higher ORR activity than Pt and it is suggested by density functional theory calculations that Pt₃Sc alloy has high stability and higher ORR activity due to filling the metal d-bands and lowers binding energy of the oxygen species respectively. Herein, we report Pt₃Sc alloy nanoparticles (NPs) dispersed over partially exfoliated carbon nanotubes (PECNTs) as a cathode catalyst for single-cell measurements of PEMFC where Pt₃Sc alloy shows a lower binding energy towards oxygen and facilitates ORR with much faster kinetics. The ORR activity of Pt₃Sc/PECNTs electrocatalyst, investigated by cyclic voltammetry, Rotating Disk electrode (RDE) and Rotating Ring Disk electrode (RRDE), shows the higher mass activity and lower H₂O₂ formation than the commercial catalyst Pt/C-TKK. Accelerated Durability Tests (ADT) was performed to evaluate the stability of catalysts in acidic medium. In single-cell measurements, Pt₃Sc/PECNTs cathode catalyst exhibits a power density of 760 mW cm⁻² at 60 °C. Our study gives an important insight into the design of a novel ORR electrocatalyst with an excellent stability and high power density of PEMFC.     

MoO2 nanocrystals down to 5 nm as Pt electrocatalyst promoter for stable oxygen reduction reaction

The single molybdenum oxide (MoO₂) crystals down to 5 nm in diameter on carbon (denoted as C-MoO₂) are synthesized based on ion-exchange principle for the first time. The structures, morphologies, chemical and electrocatalytic performances of as-synthesized nanomaterials are characterized by physical, chemical and electrochemical methods. The results indicate that electrocatalysts made with Pt nanoparticles supporting on C-MoO₂ (denoted as Pt/C-MoO₂) are highly active and stable for oxygen reduction reaction (ORR) in fuel cells. A mass activity of 187.4 mA mg⁻¹_Pt at 0.9 V is obtained for ORR, which is much higher than that on commercial Pt/C (TKK) electrocatalyst (98.4 mA mg⁻¹_Pt). Furthermore, the electrochemical stability of Pt/C-MoO₂ is more excellent than that of Pt/C (TKK). The origin of the improvement in catalytic activity can be attributed to the synergistic or promotion effect of MoO₂ on Pt. The improvement in electrochemical stability is due to the strong interaction force between Pt and MoO₂.     

Engineering the electronic structure of PtCo sites via electron injection to CoNC boosts acidic oxygen electroreduction

Inadequate performance of oxygen reduction reaction (ORR) hinders the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, we report an ORR catalyst consisting of intermetallic PtCo nanoparticles and atomically dispersed CoNC sites, exhibiting outstanding performance in the RDE test (E_1/2 = 0.906 V vs. RHE, 7 mV loss after 20,000 cycles, 0.63 A mg⁻¹_Pt of mass activity at 0.9 V). The enhancement of activity and durability is attributed to the unique structure that Pt atoms are modified by the smaller transition metal atoms Co to form PtCo intermetallic and further regulated by CoNC, the dual electronic engineering results appropriate binding energy between Pt and oxygen species. In addition, enhanced PtCo–CoNC interaction impedes the agglomeration of nanoparticles, which enables the formation of sub-5 nm PtCo intermetallic and enhances the stability. This synthesis method provides an idea for further regulating the electronic structure of Pt alloy and synthesize uniform and small intermetallic particles.     

Platinum-nickel bimetallic catalyst doped with rare earth for enhancing methanol electrocatalytic oxidation reaction

Platinum (Pt) is often used as anodic catalyst for direct methanol fuel cell (DMFC). However, platinum is difficult to achieve large-scale application because of its low stability and high cost. In this work, the electrocatalytic activity and stability of the Pt-based catalyst for methanol oxidation (MOR) are significantly improved by adding Ce and Ni to the catalyst. Additionally, the rare earth element-Pr (Dy) is also chosen to be added into the catalysts for comparison. A series of PtMNi (M = Ce, Pr, Dy) catalysts are prepared by impregnation and galvanic replacement reaction methods using carbon black as support. The electrocatalytic mass activity of PtCeNi/C, PtDyNi/C, PtPrNi/C and Pt/C is 3.92, 1.86, 1.69 and 0.8 A mg_Pt⁻¹, respectively. The mass activity of these the above four catalysts after stability measurement is 3.14, 1.49, 1.27 and 0.72 A mg_Pt⁻¹. Among them, PtCeNi/C has the highest catalytic activity. These as-prepared catalysts are also characterized by various analyzing techniques, such as TEM, HRTEM, XRD, XPS, ICP-OES, STEM, STEM-EDS elemental mapping and line-scanning etc. It shows that PtCeNi/C exhibits best catalytic activity (3.92 A mg_Pt⁻¹) among the as-obtained catalysts, 4.9 times higher than that of commercial Pt/C (0.8 A mg_Pt⁻¹). PtCeNi/C is also with excellent anti-CO poisoning ability. The outstanding catalytic performance of PtCeNi/C for the MOR is mainly attributable to uniform-sized PtCeNi nanoparticles, uniform Ni, Ce and Pt element distribution, and electron interaction among Pt-, Ni- and Ce-related species (electron transferring from Pt to CeO₂).     

Feasibility of ultra-low Pt loading electrodes for high temperature proton exchange membrane fuel cells based in phosphoric acid-doped membrane

Factors as the Pt/C ratio of the catalyst, the binder content of the electrode and the catalyst deposition method were studied within the scope of ultra-low Pt loading electrodes for high temperature proton exchange membrane fuel cells (HT-PEMFCs). The Pt/C ratio of the catalyst allowed to tune the thickness of the catalytic layer and so to minimize the detrimental effect of the phosphoric acid flooding. A membrane electrode assembly (MEA) with 0.05 mg_Ptcm⁻² at anode and 0.1 mg_Ptcm⁻² at cathode (0.150 mg_Ptcm⁻² in total) attained a peak power density of 346 mW cm⁻². It was proven that including a binder in the catalytic layer of ultra-low Pt loading electrodes lowers its performance. Electrospraying-based MEAs with ultra-low Pt loaded electrodes (0.1 mg_Ptcm⁻²) rendered the best (peak power density of 400 mW cm⁻²) compared to conventional methods (spraying or ultrasonic spraying) but with the penalty of a low catalyst deposition rate.     

Pt and Pt–Ag nanoparticles supported on carbon nanotubes (CNT) for oxygen reduction reaction in alkaline medium

In this work, we investigated the effect of the carbon nanotubes (CNT) as alternative support of cathodes for oxygen reduction reaction (ORR) in alkaline medium. The Pt and Pt–Ag nanomaterials supported on CNT were synthesized by sonochemical method. The crystalline structure, morphology, particle size, dispersion, specific surface area, and composition were investigated by XRD, SEM-EDS, TEM, HR-TEM, N₂ adsorption-desorption and XPS characterization. The electrochemical activity for ORR was evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) in alkaline medium. The electrochemical stability was researched by an accelerated degradation test (ADT). Pt/CNT showed the better electrocatalytic activity towards ORR compared with Pt–Ag/CNT and Pt/C. Pt/CNT exhibited higher specific activity (1.12 mA cm^?2 _Pt) than Pt/C (0.25 mA cm^?2 _Pt) which can be attributed to smaller particle size, Pt-CNT interaction, and Pt load (5 wt%). The Pt monometallic samples supported on CNT and Vulcan showed higher electrochemical stability after ADT than Pt–Ag bimetallic. The ORR activity of all materials synthesized proceeded through a four-electron pathway. Furthermore, the EIS results showed that Pt/CNT exhibited the lower resistance to the transfer electron compared with conventional Pt/C and Pt–Ag/CNT.     

Fe-doped CoP nanotube heterostructure enhanced the catalytic activity of Pt nanoparticles towards methanol oxidation reaction

Developing the efficient and stable anode catalysts of direct methanol fuel cell has been a pivotal requirement for its extensive commercial application. Herein, we design the Fe-doped CoP nanotube heterostructure as the co-catalyst of Pt-based catalyst via combining a facile hydrothermal with phosphorization process, subsequently, the traditional NaBH₄ reduction method is utilized to deposit Pt nanoparticles. As anticipated, Fe species have been successfully doped into CoP to generate the Fe-doped CoP nanotube heterostructure, and the involved characterizations identify that Pt–C/Fe₂–CoP catalyst exhibits admirable mass activity (1237 mA·mg⁻¹_Pt) towards methanol oxidation reaction, which is approximately 2.04 and 3.66 times as high as the Pt–C/CoP (607 mA·mg⁻¹_Pt) and Pt–C–H (338 mA·mg⁻¹_Pt). After stability test, the decline ratio of mass activity for Pt–C/Fe₂–CoP (83.43%) is markedly preferable to Pt–C/CoP (94.92%) and Pt–C–H (98.67%) catalysts. The enhanced catalytic activity and durability can be imputed to the formation of uniform Pt nanoparticles and co-catalysis effect of Fe-doped CoP nanotube heterostructure since the introduction of hetero-metal cations is able to effectively accelerate the charge transfer rate and adjust the electronic structure of material. Therefore, the fabrication of nanotube heterostructure and introduction of hetero-metal may provide a new direction to the development of other high-efficiency electrocatalysts.     

Carbon supported Pt-Y electrocatalysts for the oxygen reduction reaction

Carbon supported Pt₃Y (Pt₃Y/C) and PtY (PtY/C) were investigated as oxygen reduction reaction (ORR) catalysts. After synthesis via reduction by NaBH₄, the alloy catalysts exhibited 10-20% higher mass activity (mA mg_Pt⁻¹) than comparably synthesized Pt/C catalyst. The specific activity (μA cm_Pt⁻²) was 23 and 65% higher for the Pt₃Y/C and PtY/C catalysts, respectively, compared to Pt/C. After annealing at 900 °C under a reducing atmosphere, Pt₃Y/C-900 and PtY/C-900 catalysts showed improved ORR activity; the Pt/C and Pt/C-900 (Pt/C catalyst annealed at 900 °C) catalysts exhibited specific activities of 334 and 393 μA cm_Pt⁻², respectively, while those of the Pt₃Y/C-900 and PtY/C-900 catalysts were 492 and 1050 μA cm_Pt⁻², respectively. X-ray diffraction results revealed that both the Pt₃Y/C and PtY/C catalysts have a fcc Pt structure with slight Y doping. After annealing, XRD showed that more Y was incorporated into the Pt structure in the Pt₃Y/C-900 catalyst, while the PtY/C-900 catalyst remained unchanged. Although these results suggested that the high ORR activity of the PtY/C-900 catalyst did not originate from Pt-Y alloy formation, it is clear that the Pt-Y system is a promising ORR catalyst which merits further investigation.     

PtCo incorporated porous carbon nanofiber as a promising oxygen reduction electrocatalyst

Designing oxygen reduction reaction (ORR) catalysts with high activity and long durability is significant for the development of proton exchange membrane fuel cells. Herein, the optimized platinum nanowires are used as templates for inducing growth of cobalt-containing metal-organic framework, deriving uniform nanofibers. After the calcination, the metal ions are transferred into the nitrogen-rich porous carbon, and wrapped by the carbon skeleton to form the PtCo bimetal incorporated nanofibers as high-performance ORR electrocatalyst. The Pt₄Co@NC-900 catalyst yields high specific activity (1.37 mA cm⁻²) in comparison to Pt/C (0.38 mA cm⁻²). The mass activity (MA) of Pt₄Co@NC-900 catalyst is approximately 3.8-fold higher than that of the commercial Pt/C under acidic conditions. After the accelerated durability tests, the Pt₄Co@NC-900 catalyst presents only 16% loss in MA, while Pt/C catalyst retains 73.0% of the initial MA. The improved ORR performance can be ascribed to the synergistic interaction between Co and Pt.     

One-pot synthesis of Pt/CeO2/C catalyst for improving the ORR activity and durability of PEMFC

Oxygen reduction reaction (ORR) activity and durability of Pt catalysts should be both valued for successful commercialization of proton exchange membrane fuel cells (PEMFCs). We offer a facile one-pot synthesis method to prepare Pt/CeO₂/C composite catalysts. CeO₂ nanoparticles, with high Ce³⁺ concentration ranging from 30.9% to 50.6%, offers the very defective surface where Pt nanoparticles preferentially nuclear and growth. The Pt nanoparticles are observed sitting on the CeO₂ surface, increasing the PtCeO₂ interface. The high concentration of oxygen vacancies on CeO₂ surface and large PtCeO₂ interface lead to the strong PtCeO₂ interaction, effectively improving the ORR activity and durability. The mass activity is increased by up to 50%, from 36.44 mA mg^?1 of Pt/C to 52.09 mA mg^?1 of Pt/CeO₂/C containing 20 wt.% CeO₂. Pt/CeO₂/C composite catalysts containing 10–30 wt.% CeO₂ loss about 80% electrochemical surface area after 10,000 cycles, which is a fivefold enhancement in durability, compared to Pt/C losing 79% electrochemical surface area after 2000 cycles.     

Solution plasma method assisted with MOF for the synthesis of Pt@CoOx@N-C composite catalysts with enhanced methanol oxidation performance

The key to direct methanol fuel cells (DMFCs) is the anode catalyst for methanol oxidation reaction (MOR) which has good catalytic activity and stability. Pt@CoO_x@N-C catalysts were synthesized by compounding Pt nanoparticles and CoO_x with nitrogen-doped porous carbon (N-C). Pt nanoparticles were prepared by solution plasma technique. CoO_x@N-C are derived from zeolitic-imidazolate-framework-67 (ZIF-67) by heat treatment at 700 °C. For MOR, Pt@CoO_x@N-C exhibits an outstanding electrocatalytic performance (mass activity of 2400 mA mg_Pt⁻¹) and stability (70% remained after 300 cycles) under acidic condition, which owing to the synergistic effects among the Pt nanoparticles, CoO_x and nitrogen-doped porous carbon. Pt@CoO_x@N-C shows such mass activity superior to that of Pt/C (460 mA mg_Pt⁻¹) due to the fact that CoO can adsorb –OH in the solution and then assist Pt to oxidize the CO-like intermediates to CO₂ which improves the resistance to CO poisoning of Pt nanoparticles. Therefore, solution plasma method assisted with metal-organic frameworks have good development prospects on synthesis of highly efficient electrocatalysts.     

Composition-tunable PtCu porous nanowires as highly active and durable catalyst for oxygen reduction reaction

To accelerate the commercialization of fuel cells, many efforts have been made to develope highly active and durable Pt-based catalyst for oxygen reduction reaction (ORR). Herein, PtCu porous nanowires (PNWs) with controllable composition are synthesized through an ultrasound-assisted galvanic replacement reaction. The porous structure, surface strain, and electronic property of PtCu PNWs are optimized by tuning composition, which can improve activity for ORR. Electrochemical tests reveal that the mass activity of Pt_0.5Cu_0.5 PNWs (Pt/Cu atomic ratio of 1:1) reaches 0.80 A mg_Pt^?1, which is about 5 times higher than that of the commercial Pt/C catalyst. Notably, the improved activity of the porous nanowire catalyst is also confirmed in the single-cell test. In addition, the large contact area with the carrier and internal interconnection structure of Pt_0.5Cu_0.5 PNWs enables them to exhibit much better durability than the commercial Pt/C catalyst and Pt_0.5Cu_0.5 nanotubes in accelerated durability test.     

Cu-template-dependent synthesis of PtCu nanotubes for oxygen reduction reactions

The development of electrocatalysts with high activity and durability for oxygen reduction reaction (ORR) in acidic electrolyte environments remains a serious challenge for clean and efficient energy conversion. Synergistic effects between Pt and inexpensive metals, the d band center of Pt and catalyst morphology could adjust the adsorption and desorption of oxygen intermediates by the Pt. All the factors affect the catalytic performance of Pt-based nanocrystals. Here, we prepared Cu@PtCu₃ NWs with an average diameter of 74.9 nm for Cu and about 10 nm PtCu₃ layer. After etching, the Cu@PtCu₃ nanowires is transformed into PtCu nanotube structure, due to the removal of copper from the surface and interior. PtCu NTs for ORR shows excellent activities and durability due to the integration of structural advantages and synergistic effects. Notably, the mass activity and specific activity of PtCu NTs (0.105 A mg^?1_Pt and 0.230 mA cm^?2_Pt) are 2.0 and 3.8 times higher than that of commercial Pt/C (0.053 A mg^?1_Pt and 0.06 mA cm^?2_Pt). The etching process to change the morphology of the catalyst and alter the electronic structure of the catalyst is expected to be useful for the design of future structured Pt-based alloy nanocatalysts.     

Comparative study of the effect of TiO2 support composition and Pt loading on the performance of Pt/TiO2 photocatalysts for catalytic photoreforming of cellulose

Herein, catalytic aqueous phase photoreforming of cellulose was carried out over Pt/m-TiO₂ (i.e., mixed phase of anatase and rutile) and Pt/anatase catalysts to investigate the effect of the TiO₂ support structure and Pt loading on the production of H₂. The effect of the TiO₂ support on the properties of the resulting Pt/TiO₂ catalysts (such as actual Pt loading and BET surface area) was not significant. At low Pt loading of 0.16 wt.%, the TiO₂ supports affected the sub-nanometre Pt structures which was confirmed by the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterisation (using CO as the probe). Conversely, the effect of TiO₂ supports on larger Pt particles (on 1 wt.% catalysts) was insignificant possibly due to the reduced effect of restructuration of bigger Pt particles on the TiO₂ supports. With an increase in Pt loading from 0.16 wt% to 1.00 wt.%, the normalised H₂ production rate (with respect to the actual supported Pt amount and specific surface area of the catalysts) showed a decreasing trend over the two types of the catalysts, i.e., from 10.6 to 1.4 μmol h⁻¹ m⁻² mg_Pt⁻¹ for Pt/m-TiO₂, and from 8.5 to 1.2 μmol h⁻¹ m⁻² mg_Pt⁻¹ for Pt/anatase. Specifically, large Pt particle sizes reduced the CO₂/H₂ production from cellulose photoreforming over both Pt/m-TiO₂ and Pt/anatase catalysts, indicting an important role played by Pt particle size in photoreforming. Interestingly, in this study, the m-TiO₂ supported catalysts only showed the benefits of enhanced charge separation across the phase junction in producing H₂ with small Pt particles (at sub-nanometre), whilst, when large Pt particles (at around 1–2 nm) were supported, such a benefit was not significant in cellulose photoreforming. The promoting effect of small, sub-nm particles is attributed to the better capture of photoelectrons from bulk TiO₂ and better activity of H⁺ coupling on small Pt particle. Further fundamental study on such guest-host interactions is devised to optimise Pt/TiO₂ catalysts for improving H₂ production from photoreforming reactions.