Young Researcher’s Hybrid School on Theory and Simulation in Electrochemical Conversion Processes – 23-26/05/2023, Paris
State of the Art and Workshop Objectives
Electrochemical processes are the cornerstone of green chemistry and energy-conversion devices. The accurate modelling of electrocatalytic reactions in the presence of electric fields, in particular, is key to the study of reduction/oxidation processes involved in the synthesis of value-added chemicals, as well as to shedding light on the mechanisms underlying the origin of life (i.e., prebiotic chemistry). The theoretical treatment of electrochemical phenomena is characterised by a high level of complexity. Non-trivial chemistry and electrodynamics are intertwined to form intrinsically multiscale systems, with certain aspects that can be treated only at the atomistic level, while others must be treated as a continuum. From a methodological perspective, the simulation of a system’s dynamics at the atomic scale in the presence of applied potentials benefits from a number of advancements that have brought the modelling of electrode-reactants-electrolyte interactions from a fairly quantitative to a strikingly accurate predictive ability. On the one hand, grand-canonical density functional theory (GC-DFT) methods have been extensively used to simulate the quantum properties of electrochemical interfaces and, due to their ab-initio nature, have proven to be particularly suited for the simulation of electrochemical reactions and the rationalisation of absorption mechanisms. On the other hand, constant-potential molecular dynamics (MD) methods have been used to model complete electrochemical cells under an applied voltage, paving the way to the atomistic simulation of energy-storage devices. Recent advancements in classical density functional theories (c-DFT) make it possible to compute accurate solvation free-energies of electrochemical interfaces and gain new insights on the thermodynamic stability of electrochemical products and reactants. Finally, the modern theory of polarisation and its application to deal with finite electric fields or electric displacement fields have fostered recent advancements in the modelling of metal-electrolyte interactions, allowing for an explicit treatment of the electrolyte while maintaining a quantum-level description of the system. On this front, equivariant and long-range machine-learning methods hold great promise in overcoming the time and length scale limit associated with current ab-initio approaches and predicting the non-local electronic response of the electrochemical interface under applied fields. The event aims at bringing together a multidisciplinary array of leading experts and young researchers working on the theory and simulation of electrochemical conversion processes.
By promoting the discussion of methods and approaches leveraging different philosophies, we expect the workshop to achieve three main objectives: 1) Create a koiné within which method-oriented and application-oriented practitioners can more easily and fruitfully exchange ideas and disseminate cutting-edge achievements. To this end, introductory lectures, a panel discussion and ample time for informal discussion during coffee breaks are foreseen. 2) Offer to young researchers a complete and pedagogical overview of the state-of-the-art in the modelling of electrochemical processes. Towards this objective, the workshop will include: i) introductory lectures to present in detail the theories and computational methods underlying the simulation of electrochemical systems, ii) hands-on tutorials to nurture practical experience in the dedicated codes and software, i.e., constant-potential classical MD, grand-canonical DFT, finite-field methods with fixed electric or displacement field calculations, iii) coffee breaks and poster sessions to stimulate informal exchanges among junior and experienced researchers. 3) Identify challenging frontier problems which are now accessible thanks to the latest advancements in the field and discuss the criticalities related to pressing technological and environmental problems. To this end, discussion among participants will be promoted by means of multi-thematic invited lectures, time for informal exchanges during coffee breaks and a panel discussion.
Outcomes
The workshop introduced to the audience five state-of-the-art community codes in the field of electrochemistry, with tutorial sessions showcasing specific applications and illustrating actions and requirements inherent to broad case studies. These included: i) MetalWalls, a classical molecular dynamics code dedicated to electrochemical systems; ii) CP2K, with a particular focus on Finite field density functional theory molecular dynamics; iii) GPAW, with a deep-dive on Electrochemical thermodynamics and kinetics with grand canonical ensemble DFT; iv) Quantum Espresso and Quantum Environ, and their use for Electrochemical interfaces simulations; v) tranSIESTA, and the Non-Equilibrium Green’s Functions formalism for electrochemical cell simulations.
From the application perspective, during the workshop applications of advanced theory and software developments have been discussed in the context of a broad array of domains. These include (but are not limited to): electrified metal-water and oxide-water interfaces, carbon based electrodes and water-carbon interfaces, reactive processes at electrochemical interfaces (e.g., catalytic reactions and corrosion), spectroscopy at aqueous interfaces, electrochemistry in solution (e.g., prebiotic chemistry), transport phenomena in electrolytes.
During the course of the event, possible research trends have emerged. Significant examples are:
- The integration of machine learning approaches to partly by-pass ab initio approaches.
- The importance of advancing the state-of-the-art in software engineering to empower researchers with larger-scale modelling via more efficient codes.
- The need to go beyond idealised models to move from qualitative to quantitative agreement with experiments.
- The potential and relevance of models encompassing or interfacing different levels of theory (ab initio+atomistic empirical models+cDFT) at the same time.
Throughout the school, the relevance of cross-fertilization of ideas and know-how to account for the multiple scales involved in the electrochemical problem was also a recurring emergent theme.
The benefit of a tailored event, where technical detail about numerous codes and approaches were discussed in an open and pedagogical manner, was highly appreciated. In the future we foresee the integration of expertise and perspective by also including experimentalist and/or industry representatives, to strengthen the interdisciplinarity of the event and consider novel outstanding challenges.
Community needs
The community needs emerged from our workshop and discussion are linked to both capacity and research coordination.
From a capacity standpoint, computational needs inherent to the simulation of large complex atomistic models with a good accuracy may result critical, in particular if only modest computational budgets are available. Computational expenses are quite tasking especially for purely ab initio approaches. Computational cost may result moderate in parametrized approaches, which nevertheless may suffer inaccuracies due to the constrained expressivity in the parametric function to evaluate energy, forces, and dipoles. Along these lines, the continuous development of polarizable empirical force fields is a viable strategy toward more and more reliable simulations.
Good software engineering practices and advancement code-developments (e.g., GPU-acceleration) would greatly benefit the community and are very much needed to democratise access to methods and performances.
The integration of advanced machine learning method that are endowed with the same generality of ab initio methods, but enable to decrease by one or more orders of magnitude the cost of a calculation, represent a promising methodological advancement to satisfy the need to run realistic complexity in the simulations at an affordable computational cost. The development of these methods is still emergent nevertheless. Machine learning developments are particularly advisable for the construction of surrogate models able to correctly address long-range electrostatic effects.
From a research coordination standpoint, the community benefits from further cross-fertilization of ideas and a focus on the multi-scale nature of electrochemical processes. Structural features at electronic, atomistic, nanoscopic, and microscopic level all affect, e.g., the activity and selectivity of a catalyst. While we hope that this event acted as a stepping stone in building links across different groups and specialisations, further steps in this direction are needed.
Not many workshops have been organised on the topic of this school this year. The feedback from the invited speakers, contributed speakers, and attendees, suggested a good appreciation for a focused event, with a technical-oriented program. While we do not foresee the immediate need for formally establishing a workshop series, we plan to organise a new edition in May 2025.
Funding
The present workshop was funded by CECAM, PSI-K, and ENS-PSL. For future events, we will consider application to Societies in Chemistry, Electrochemistry, and Catalysis. Towards establishing recurring (e.g. bi-annual) schools for young researchers, synergies with these entities could in fact be highly instrumental. Gathering funding from additional sources will further allow to accommodate more young researchers as in-person attendees, which we see as a possible additional need in future events.
Dissemination
TSECP gathered scientists at the interface between chemical physics, physical chemistry, catalysis, materials engineering, and theoretical chemistry. From a demographic standpoint, the attendees consisted of a large majority of young researchers, with a fair gender balance both among participants and speakers. 14 different countries (with 3 non-continental Europe Nations) found a representative among the participants. We thus hope that the ideas and know-how disseminated during the event will be thus likely exploited by several other communities worldwide. All lecture slides and recordings are archived on the conference’s website for anyone to follow, facilitating dissemination in the years to come ( https://www.youtube.com/@TSECP-School ). Overall, the positive response from the participants of TSECP workshop strongly motivates another edition in the future, possibly every two years to allow both continuity and new significant development to be achieved and disseminated.
Scientific, Technologic, and Societal Impact
TSECP focuses on advancing research in electrochemistry by disseminating both the theoretical foundations as well as presenting the state-of-the-art and beyond to young researchers. Our primary goal was to train a young generation of scientists with a broad vision and strong technical skill to tackle complex challenges in the theory and simulation of electrochemical processes. In the long-term, we hope that this training and technical capacity-building was beneficial to the professional life of researchers that will work in green energy and chemistry, with an academic, industrial, or policymaking role.
In this regard, the electrification of society will in fact play a key role in transforming our economy while meeting highly desired techno-economic and socio-environmental objectives, such as the UN Sustainable Development Goals (SDGs). The discovery and application of new electrochemical processes could indeed represent a turning point towards CO2 neutrality, closed-loop production on essential platform molecules, and in green energy.
In recent years, numerical methods in the field of electrochemistry made leaps, moving from niche application to almost approaching a realistic complexity in the models that are simulated. These advancements include the design of sustainable conversion reactions, efficient manufacturing processes, and the creation of high-performance materials for green energy solutions like photovoltaics and lightweight, robust metals for transportation.
In the field of theoretical electrochemistry, important milestones have been put forward concerning the theoretical assessment of interfaces in different conditions (constant potential vs constant charge) and their reliable simulation. Although algorithm design and theoretical understanding have made substantial progress, the practical implementation of these approaches on a large scale is still in its early stages. However, it holds the potential to uncover new stable materials and facilitate the design of unprecedented materials.
While the current event did not foresee the participation of industry representatives, we will consider this for next events, to enrich the experience of the audience and facilitate the collaboration between academic experts and industry. Potential partners are emerging European holdings in the manufacturing of fuel cells and other electrochemical devices, e.g., De Nora (IT), Thyssenkrupp Nucera (DE).