Human beings might have the means to all what they can possibly imagine, but they still cannot do anything better than growing on a consistent basis. This tendency to get better, no matter the situation, has brought the world some huge milestones, with technology emerging as quite a major member of the group. The reason why we hold technology in such a high regard is, by and large, predicated upon its skill-set, which guided us towards a reality that nobody could have ever imagined otherwise. Nevertheless, if we look beyond the surface for one hot second, it will become abundantly clear how the whole runner was also very much inspired from the way we applied those skills across a real world environment. The latter component, in fact, did a lot to give the creation a spectrum-wide presence, and as a result, initiate a full-blown tech revolution. Of course, this revolution then went on to scale up the human experience through some outright unique avenues, but even after achieving a feat so notable, technology will somehow continue to bring forth the right goods. The same has turned more and more evident in recent times, and assuming one new discovery ends up with the desired impact, it will only put that trend on a higher pedestal moving forward.

The researching team at Pacific Northwest National Laboratory (PNNL) has successfully developed a mechanism, which can inform the development of new and more effective catalysts for abating NO_x (polluting reactive nitrogen oxide gases) emissions from combustion engines burning diesel or low-carbon fuels. Now, while electrification of automotive vehicles is already reducing emissions from many mobile sources, emissions coming from hard-to-electrify sectors like farming and other off-road vehicles still pose a massive environmental challenge. On top of that, it is becoming increasingly difficult to realize an efficient catalytic reduction, considering most efficient diesel engines of today tend to produce inadequate heat for driving the desired catalytic reaction. Fortunately enough, the development in question solves that conundrum big time. But how did the researchers land on this mechanism? Well, they were actually comparing the efficacy of a series of best-in-class copper-based catalysts when they noticed an anomaly. This anomaly talked to how one of the catalysts, denoted Cu/LTA, was a whopping 40% less effective at 180 °C than its counterparts, and notably enough, the stated anomaly remained firmly in place even after more reaction sites were dropped within the mix. In a bid to better understand the problematic catalyst, the researchers would apply electron paramagnetic resonance spectroscopy, which revealed to them a substantial amount of copper than what was present in other similar elements. Such a quantity meant the copper was accumulating rather than reacting. The team then used certain theoretical calculations to support their discovery, a stage where lower acidity proportions was deemed as the primary culprit.

“We wanted to understand what really caused this catalyst to be less active even though there are more active sites,” said Feng Gao, a staff scientist in PNNL’s Catalysis Science Group and the lead author of the paper explaining their study. “Its acidity is lower than the other two. Mainly, it is the lower acidity that makes the intermediate less reactive.”

Next up, the researchers roped in hydrothermal aging to reduce the acid sites in the other catalysts. The move confirmed their initial ideas, considering it reduced the efficiency displayed by these catalysts.

“A lot of the research has focused on the role of copper: how copper has to form complexes, and actually has to move around in this structure,” said Kenneth Rappe, a chief engineer and Applied Catalysis team leader at PNNL. “Then there’s long been a debate as to, okay, what’s the role of the acidity? It’s more than that. It actually plays an active, participating role. The active copper complex that forms, in the absence of acidity, actually doesn’t drive the reaction. It gets confined in space.”

Talk about how the discovery benefits an automotive industry trying to become more environmental-friendly, the answer is rooted in the way selective catalytic reduction (SCR) of NO_x leverages a reductant, typically ammonia, and a catalyst to convert NO_x to nitrogen, water, and carbon dioxide. Hence, armed with the new piece of information, car manufacturers and researchers should be extensively prepared to pursue more efficient catalytic reduction of NO_x in industrial combustion engines burning diesel or low-carbon fuels. However, this isn’t all. For the future, the researchers plan on working with catalyst manufacturers, engine manufacturers, or both to improve the current state of the art in SCR for those same combustion engines.

“The acid sites are an important component to drive this reaction at low temperatures and a key consideration for designing superior catalysts that will be more active at lower temperatures,” Rappe said. “It is a major development. This field has been so intensely studied. This is a significant advancement because it gives us another tool to actually improve these catalysts.”