What happened 

Shares of Plug Power (PLUG -1.25%), a hydrogen fuel cell company, had surged by 10.8%  this week as of early afternoon Friday, according to data from S&P Global Market Intelligence. A couple of bits of news appeared to be driving those gains. 

First, the company signed an agreement with a key supplier that management said will help it reach its revenue goals over the next several years. Additionally, Honda made an announcement regarding its long-term plans to develop new hydrogen fuel cell vehicles.

Despite this week's gains, Plug Power's highly volatile stock remains down by about 20% over the past year. 

So what

Plug Power's stock got its first boost of the week Tuesday when the company said that it had signed an agreement with parts supplier Johnson Matthey (LSE: JMAT). Plug Power said in a press release that the deal will help the company meet its needs for catalysts, membranes, and catalyst-coated membranes.  

More importantly, the company said the partnership will help it reach its revenue goals of $5 billion in sales by 2026 and $20 billion in sales by 2030. 

Investors' optimism about Plug Power increased Thursday after Honda said that it is expanding its hydrogen fuel cell business. The automaker noted that it has been co-developing a hydrogen fuel cell system with General Motors, but said it aims to improve on that platform, and that its goal is to sell a few hundred thousand fuel cell vehicles per year by the second half of the 2030s. 

Investors appear to have latched onto that news as a good sign for the future of the hydrogen fuel cell market. 

Now what 

While Plug Power's share price gains were impressive this week, investors may still want to be cautious with this stock. 

Plug Power's management recently told investors that the company will miss its prior revenue estimates for 2022. It now expects to report that sales grew in the 45% to 50% range, compared to its previous guidance for 80% growth. 

Plug Power's stock remains volatile, and in the wake of the company's significant revenue guidance cut, investors probably shouldn't be overly upbeat about this week's news. 

Investors will get a clearer picture of how the company is doing when it delivers its fourth-quarter results. That report is likely to come out early next month.