{"id":"f1e79e26-2f37-439d-9ffc-101c27a288f5","arxiv_id":"2606.25992","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":3.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"A 3D numerical model shows ammonia reduces proton conductivity in PEM and anode catalyst layer of fuel cells, with higher temperature, humidity, and thinner membranes mitigating the effect.","lead":"This preprint describes a numerical study on how ammonia impurities poison proton exchange membrane fuel cells used with ammonia-derived hydrogen. Smart readers might care because ammonia is seen as a promising way to store and transport hydrogen for clean energy, and understanding poisoning is key to making it work.","discovery_kind":"new_application","skeptic_critique":{"model":"grok-4.3","headline":"No significant objection identified","rationale":"The reader's assessment is based on the abstract alone and correctly flags model accuracy as the key uncertainty. With no full text equations or results available for scrutiny, no additional load-bearing concern (e.g., internal inconsistency in derivations or parameter choices) can be identified. The verdict therefore remains UNVERDICTED.","tokens_in":1678,"tokens_out":259,"duration_ms":8927,"concrete_test":"Re-run the 3D model with the ammonia conductivity reduction term removed from the PEM and CL domains; if the predicted performance drop disappears while all other transport equations remain unchanged, the claimed mechanism is directly attributable to that term.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is that a 3D numerical model demonstrates ammonia reduces proton conductivity in the PEM and anode CL, with mitigation via temperature, humidity, and thickness. Because the full manuscript (including governing equations, boundary conditions, ammonia reaction kinetics, and any validation) is referenced but not reproduced here, no independent technical inconsistency can be located in the argument itself. The reader's weakest assumption correctly isolates the model's fidelity as the load-bearing element; absent the actual equations or data, no further internal flaw is detectable.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript develops a three-dimensional numerical model of proton exchange membrane fuel cells (PEMFCs) incorporating ammonia impurities to investigate transport processes and the poisoning mechanism. It examines the effects of ammonia concentration, operating temperature, humidity, and membrane thickness on performance, analyzing distributions of proton conductivity, current density, and dissolved water content. The central claims are that ammonia substantially reduces proton conductivity in both the PEM and anode catalyst layer, thereby diminishing cell performance, while higher temperature, higher humidity, and decreased membrane thickness can mitigate the poisoning (with the latter potentially causing less uniform current distribution).","tokens_in":1752,"tokens_out":342,"duration_ms":18170,"significance":"If the numerical model is shown to be accurate, the parametric results on conductivity reduction and mitigation strategies would be significant for PEMFC applications using ammonia-derived hydrogen, providing practical guidance on operating conditions to alleviate poisoning effects.","major_comments":[{"comment":"Model setup and validation (referenced in the methods and results sections): The central claims rest entirely on outputs from the 3D numerical model, yet no validation against experimental data, error analysis, or benchmark comparisons (e.g., ammonia-free polarization curves) is provided. This makes it impossible to assess whether the reported conductivity reductions and mitigation trends are physically reliable.","section":"Model description and validation"}],"minor_comments":[{"comment":"The abstract states qualitative trends but omits the specific ammonia concentration range examined and any quantitative performance metrics (e.g., voltage loss percentages), which would improve clarity.","section":"Abstract"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the constructive feedback. We address the single major comment below.","responses":[{"response":"We agree that explicit validation strengthens the manuscript. The model employs well-established governing equations for species, charge, and energy transport in PEMFCs, with ammonia effects incorporated via literature-derived conductivity correlations. However, the current version lacks direct benchmark comparisons. In the revised manuscript we will add polarization-curve comparisons against published experimental data for ammonia-free operation, include a quantitative error analysis, and discuss parameter uncertainty. These additions will allow readers to evaluate the physical reliability of the reported trends.","revision_made":"yes","referee_comment":"[Model description and validation] Model setup and validation (referenced in the methods and results sections): The central claims rest entirely on outputs from the 3D numerical model, yet no validation against experimental data, error analysis, or benchmark comparisons (e.g., ammonia-free polarization curves) is provided. This makes it impossible to assess whether the reported conductivity reductions and mitigation trends are physically reliable."}],"tokens_in":1252,"tokens_out":234,"duration_ms":17504,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main point from this paper is a three-dimensional numerical model of proton exchange membrane fuel cells that includes ammonia impurities. It concludes that ammonia reduces proton conductivity in both the PEM and the anode catalyst layer, which hurts overall cell performance. The study also finds that raising the operating temperature or humidity can reduce the poisoning effect, and that a thinner membrane helps but can make the current distribution less uniform.\n\nOn the positive side, the work connects to the practical issue of using ammonia as a hydrogen carrier, where trace ammonia can remain after decomposition. The analysis from the perspectives of proton conductivity, current density, and dissolved water content distributions is a reasonable way to look at the transport processes. The parametric studies on ammonia concentration, temperature, humidity, and membrane thickness give a sense of how operating conditions matter.\n\nThe main weakness is that everything rests on the simulation without any reported validation. There are no comparisons to experimental data, no error bars, and no discussion of how the ammonia poisoning is incorporated into the model equations. For claims about specific reductions in conductivity or the degree of mitigation, this is a problem because we can't tell if the model is accurate or if it's just producing plausible-looking outputs. The abstract doesn't even hint at how the model was set up or tested.\n\nThis paper is aimed at people in the fuel cell modeling community who deal with impurity effects or at engineers working on ammonia-based hydrogen systems. A reader looking for new modeling techniques won't find much, but someone wanting to see the impact of these parameters in a 3D setup might get some ideas.\n\nI think it deserves to go to peer review. The topic is timely for clean energy applications, and the modeling is the kind of thing that can be checked and improved by referees. It won't change the field, but it could be a solid incremental contribution if the methods hold up.","headline":"This is a standard 3D simulation of ammonia poisoning in PEM fuel cells that reports conductivity drops and mitigation trends but rests entirely on unvalidated model outputs.","tokens_in":2219,"tokens_out":449,"would_cite":false,"duration_ms":16113,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Ammonia impurities reduce proton conductivity in PEM fuel cells, lowering performance.","keywords":["ammonia poisoning","PEM fuel cells","proton conductivity","numerical model","transport process","hydrogen carrier","operating conditions"],"falsifier":"An experiment that measures proton conductivity in the membrane and anode layer at the modeled ammonia concentrations and finds no reduction would falsify the central claim.","tokens_in":2589,"feed_emoji":"⚡","tokens_out":581,"duration_ms":17346,"temperature":0.7,"pith_summary":"The paper builds a three-dimensional numerical model of proton exchange membrane fuel cells to examine the effects of trace ammonia impurities from decomposed ammonia used as a hydrogen source. It establishes that ammonia poisons the cell mainly by cutting proton conductivity in the membrane and the anode catalyst layer. The study then maps how this effect changes with ammonia concentration, operating temperature, humidity levels, and membrane thickness, using distributions of conductivity, current density, and water content. A sympathetic reader would care because ammonia offers a compact way to store and transport hydrogen, yet any persistent impurity could limit the reliability of fuel-cell systems that rely on it.","feed_headline":"Ammonia reduces PEM fuel cell proton conductivity","feed_subtitle":"Higher temperature and humidity lessen the effect; thinner membranes help but reduce current uniformity","key_machinery":"Three-dimensional numerical model of PEM fuel cells that incorporates ammonia impurities and tracks the resulting changes in proton conductivity, current density, and dissolved water content across the cell.","core_discovery":"The results show that ammonia diminishes the cell performance by substantially reducing the proton conductivity of both the PEM and the anode catalyst layer. Higher operating temperatures and higher operating humidity can alleviate ammonia poisoning. Decreasing the membrane thickness can also help to mitigate ammonia poisoning, but may lead to less uniform current distribution.","pith_inferences":["Systems that generate hydrogen from ammonia may need to pair fuel cells with tighter impurity controls or adjusted operating set-points to preserve output.","The thickness-conductivity trade-off identified here suggests a design choice between poisoning tolerance and electrical uniformity that would appear in any scaled ammonia-hydrogen fuel-cell stack.","If the modeled conductivity drop is confirmed, real-time monitoring of local current density could serve as an early indicator of ammonia exposure in operating cells."],"forward_implications":["Higher operating temperatures reduce the performance loss caused by ammonia.","Higher operating humidity reduces the performance loss caused by ammonia.","Thinner membranes reduce the performance loss caused by ammonia but produce less uniform current distribution across the cell."],"fun_headline_variants":["Ammonia lowers proton conductivity in PEM and anode layers","Higher temperature and humidity reduce ammonia poisoning","Thinner membranes mitigate ammonia poisoning but uneven current","Ammonia reduces PEM fuel cell performance via conductivity loss"],"cache_read_input_tokens":2112,"weakest_assumption_plain":"The three-dimensional numerical model accurately captures the transport processes and underlying poisoning mechanism of ammonia impurities in PEM fuel cells.","fun_headline_variants_meta":{"raw":{"variants":["Ammonia lowers proton conductivity in PEM and anode layers","Higher temperature and humidity reduce ammonia poisoning","Thinner membranes mitigate ammonia poisoning but uneven current","Ammonia reduces PEM fuel cell performance via conductivity loss"]},"model":"grok-4.3","cost_usd":0.013344,"raw_usage":{"total_tokens":5744,"prompt_tokens":598,"num_sources_used":0,"completion_tokens":50,"cost_in_usd_ticks":133437000,"prompt_tokens_details":{"text_tokens":598,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":5096,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":598,"tokens_out":50,"duration_ms":36797,"temperature":1.0,"reasoning_tokens":5096,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-06-25T19:42:38.214096+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"An experiment that measures proton conductivity in the membrane and anode layer at the modeled ammonia concentrations and finds no reduction would falsify the central claim.","supporting_citations":[],"review_version":1}