The growing demand for sustainable energy technologies has driven the search for multifunctional electrocatalysts capable of operating efficiently across multiple electrochemical reactions. In this work, we report the successful solution-phase synthesis of an ordered Pd3Ni intermetallic compound, a system traditionally considered difficult to obtain due to the tendency of adjacent transition metals to form disordered alloys rather than ordered phases. The ordered Pd3Ni intermetallic (Pd3Ni-IM) exhibits exceptional tetrafunctional electrocatalytic activity, simultaneously supporting hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and ethanol oxidation reaction (EOR). This rare combination enables its application in both water electrolysers and fuel cell technologies. A key concept introduced in this study is “local entropy tailoring,” where the reduced configurational entropy of the ordered intermetallic lattice, compared to its alloy counterpart, leads to enhanced site-specific structural stability. Differential scanning calorimetry and extensive structural analysis confirmed this entropy-driven stabilisation. To distinguish the reaction mechanism at the atomic level between ordered and disordered Pd3Ni compounds, various operando spectroscopic and analytical techniques have been used.
Differential electrochemical mass spectrometry (DEMS) measurements, carried out using a Hiden HPR-40 DEMS system (Type Cell A), played a crucial role in elucidating the reaction pathways and product formation during electrochemical operation. During ethanol oxidation in alkaline media, DEMS enabled real-time detection of reaction products, revealing the formation of CO2 along with CH3CHO and CH3COOH for the Pd3Ni-IM catalyst. This directly confirmed complete C-C bond cleavage and a 12-electron transfer pathway. In contrast, the disordered Pd3Ni alloy catalyst showed no CO2 evolution, indicating only partial oxidation via a 4-electron pathway.
Figure (a) Full Hiden HPR-40 DEMS setup.
Figure (b) Type A cell with electrolyte inlet and outlet pipes.
These observations provided decisive mechanistic evidence for the superior catalytic behaviour of the ordered intermetallic. Here, in-situ ATR-FTIR captures the evolution of surface-bound reaction intermediates and their time-dependent transformation during EOR, while DEMS simultaneously provides direct, real-time detection of volatile and gaseous products formed at the electrode-electrolyte interface. The complementarity of these operando techniques enables clear correlation between surface chemistry, C-C bond cleavage, and electron-transfer pathways, making their combined application a powerful approach for mechanistic elucidation of complex electrocatalytic reactions. In addition, DEMS analysis during HER and OER confirmed the simultaneous evolution of H2 and O2, further demonstrating the multifunctional nature of the Pd3Ni-IM catalyst.
Post-reaction PXRD studies revealed that the ordered intermetallic phase remains intact under HER, ORR, and EOR conditions up to 1.2 V vs RHE, while higher anodic potentials during OER induce a transition toward a disordered alloy phase. This phase transformation obtained from PXRD is well supported by in-situ XAS and in-Raman spectroscopic analysis during OER. This phase evolution highlights the critical role of pH and operating potential in maintaining intermetallic order under working conditions. Overall, this study demonstrates how DEMS analysis can provide deep mechanistic insights and guide the rational design of robust, multifunctional electrocatalysts for next-generation energy conversion systems.
Figure (c) Type A cell with electrolyte inlet and outlet pipes.
Project Summary by: Sebastian Chirambatte Peter, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur, Bengaluru, Karnataka 560064, India.
Paper Reference: Mondal, S., Sarkar, S., Kediya, S., Riyaz, M., Singh, A., Das, S.,
Bagchi, D., Burman, R., Dutta, N., Singh, A. K., Radhakrishnan, M. and Peter, S. C. (2026) ‘Unravelling the Growth Mechanism of Local Entropy Tailored Intermetallic Pd 3 Ni Exhibiting Tetrafunctional Activity in a Water Electrolyzer and Fuel Cell.’ ACS Nano. American Chemical Society (ACS), 20(4) pp. 3886–3903. DOI: 10.1021/acsnano.5c21752.
Hiden Product: HPR-40 DEMS.
