Potential- and Time-Dependent Dynamic Nature of an Oxide-Derived PdIn Nanocatalyst during Electrochemical CO2_2 Reduction

Electrochemical reduction of CO$_2$ into valuable fuels and chemicals is a promising route of replacing fossil fuels by reducing CO$_2$ emissions and minimizing its adverse effects on the climate. Tremendous efforts have been carried out for designing efficient catalyst materials to selectively produce the desired product in high yield from CO$_2$ by the electrochemical process. In this work, a strategy is reported to enhance the electrochemical CO$_2$ reduction reaction (ECO$_2$RR) by constructing an interface between a metal-based alloy (PdIn) nanoparticle and an oxide (In$_2$O$_3$), which was synthesized by a facile solution method. The oxide-derived PdIn surface has shown excellent eCO$_2$RR activity and enhanced CO selectivity with a Faradaic efficiency (FE) of 92.13% at −0.9 V (vs RHE). On the other hand, surface PdO formation due to charge transfer on the bare PdIn alloy reduces the CO$_2$RR activity. With the support of in situ (EXAFS and IR) and ex situ (XPS, Raman) spectroscopic techniques, the optimum presence of the Pd–In–O interface has been identified as a crucial parameter for enhancing eCO$_2$RR toward CO in a reducing atmosphere. The influence of eCO$_2$RR duration is reported to affect the overall performance by switching the product selectivity from H$_2$ (from water reduction) to CO (from eCO$_2$RR) on the oxide-derived alloy surface. This work also succeeded in the multifold enhancement of the current density by employing the gas diffusion electrode (GDE) and optimizing its process parameters in a flow cell configuration

Ultralow non-noble metal loaded MOF derived bi-functional electrocatalysts for the oxygen evolution and reduction reactions

The rational design of efficient electrode materials for fuel cells, water oxidation, and metal–air batteries is now cutting-edge activity in renewable energy research. In this regard, tuning activity at the molecular level is one of the most challenging problems. Here, we have strategically employed two isophthalate-based ligands to tune the molecular structure and chemical bonding of three Co-based MOFs at the atomic level. MOFs were well characterized by single-crystal X-ray diffraction, IR spectroscopy, and X-ray absorption spectroscopy. The assembly of Co in these three novel MOFs at the atomic level dictates the catalytic activity towards the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The catalytic activity of these MOFs has been boosted further upon annealing thereby forming highly efficient noble-metal-free Co-single atom catalysts where the amount of cobalt is extremely low

In Situ Mechanistic Insights for the Oxygen Reduction Reaction in Chemically Modulated Ordered Intermetallic Catalyst Promoting Complete Electron Transfer

The well-known limitation of alkaline fuel cells is the slack kinetics of the cathodic half-cell reaction, the oxygen reduction reaction (ORR). Platinum, being the most active ORR catalyst, is still facing challenges due to its corrosive nature and sluggish kinetics. Many novel approaches for substituting Pt have been reported, which suffer from stability issues even after mighty modifications. Designing an extremely stable, but unexplored ordered intermetallic structure, Pd$_2$Ge, and tuning the electronic environment of the active sites by site-selective Pt substitution to overcome the hurdle of alkaline ORR is the main motive of this paper. The substitution of platinum atoms at a specific Pd position leads to Pt$_{0.2}$Pd$_{1.8}$Ge demonstrating a half-wave potential (E$_{1/2}$) of 0.95 V vs RHE, which outperforms the state-of-the-art catalyst 20% Pt/C. The mass activity (MA) of Pt$_{0.2}$Pd$_{1.8}$Ge is 320 mA/mg$_{Pt}$, which is almost 3.2 times better than that of Pt/C. E$_{1/2}$ and MA remained unaltered even after 50,000 accelerated degradation test (ADT) cycles, which makes it a promising stable catalyst with its activity better than that of the state-of-the-art Pt/C. The undesired 2e$^–$ transfer ORR forming hydrogen peroxide (H$_2$O$_2$) is diminished in Pt$_{0.2}$Pd$_{1.8}$Ge as visible from the rotating ring-disk electrode (RRDE) experiment, spectroscopically visualized by in situ Fourier transform infrared (FTIR) spectroscopy and supported by computational studies. The effect of Pt substitution on Pd has been properly manifested by X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). The swinging of the oxidation state of atomic sites of Pt$_{0.2}$Pd$_{1.8}$Ge during the reaction is probed by in situ XAS, which efficiently enhances 4e$^–$ transfer, producing an extremely low percentage of H$_2$O$_2$

Morphology‐Tuned Pt3_3Ge Accelerates Water Dissociation to Industrial‐Standard Hydrogen Production over a wide pH Range

The discovery of novel materials for industrial-standard hydrogen production is the present need considering the global energy infrastructure. A novel electrocatalyst, Pt$_3$Ge, which is engineered with a desired crystallographic facet (202), accelerates hydrogen production by water electrolysis, and records industrially desired operational stability compared to the commercial catalyst platinum is introduced. Pt$_3$Ge-(202) exhibits low overpotential of 21.7 mV (24.6 mV for Pt/C) and 92 mV for 10 and 200 mA cm$^{−2}$ current density, respectively in 0.5 m H$_2$SO$_4$. It also exhibits remarkable stability of 15 000 accelerated degradation tests cycles (5000 for Pt/C) and exceptional durability of 500 h (@10 mA cm$^{−2}$) in acidic media. Pt$_3$Ge-(202) also displays low overpotential of 96 mV for 10 mA cm$^{−2}$ current density in the alkaline medium, rationalizing its hydrogen production ability over a wide pH range required commercial operations. Long-term durability (>75 h in alkaline media) with the industrial level current density (>500 mA cm$^{−2}$) has been demonstrated by utilizing the electrochemical flow reactor. The driving force behind this stupendous performance of Pt$_3$Ge-(202) has been envisaged by mapping the reaction mechanism, active sites, and charge-transfer kinetics via controlled electrochemical experiments, ex situ X-ray photoelectron spectroscopy, in situ infrared spectroscopy, and in situ X-ray absorption spectroscopy further corroborated by first principles calculations